# HG changeset patch # User anoop # Date 1286576766 -19800 # Node ID c7f0069d698af1b5d9295d43279f259f77456402 # Parent 25b4e962b55eb600fc43703782f95463fa875112 added base scripts and questions except for matrices and other-type-of-plots. previous commit only removed unwanted files. diff -r 25b4e962b55e -r c7f0069d698a dictionaries/questions.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/dictionaries/questions.rst Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,102 @@ +Objective Questions +------------------- + +.. A mininum of 8 questions here (along with answers) + +1. Container-ship of values can be checked in a python dictionary + + a. True + #. False + +Answer: False + +2. Container-ship of only keys can be checked in a python dictionary + + a. True + #. False + +Answer: True + +3. The value in a dictionary can be + + a. String + #. Integer + #. Any data type + #. None + +Answer: Any data type + +4. Python lists can be made as a key in dictionaries. + + a. True + #. False + +Answer: False + +5. Given a python dictionary ``x = {'a' : 1, 'b' : 2, 'c' : 3, 'd' : + 4}``. When printed using ``print x`` will generate the output in + the order. {key-value pair ``'a':1`` identified as a, ``'b':2`` + identified as b and so on} + + a. a, b, c, d + #. d, c, b, a + #. a, c, b, d + #. b, d, a, c + #. Cannot predict + +Answer: Cannot predict + +6. The python dictionary ``x = {'a' : ['a', 'b', 'c'], 'b' : (1, 2, 3), + 1 : {1 : 'one', 2 : 'two'}, 10 : {10 : 'ten', 11 : 'eleven'}}`` is + invalid. + + a. True + #. False + +Answer: False + +7. Consider the python dictionary ``x = {'a' : ['a','b','c'], 'b' : + (1, 2, 3), 1 : {1 : 'one', 2 : 'two'}, 10 : {10 : 'ten', 11 : + 'eleven'}}``. And after applying the code below, what will be the + output of ``print x['a']`` + :: + + x['a'].extend(['d', 'e']) + x['a'][3] = x[10] + + a. Code will result in error + #. ['a', 'b', 'c', {11: 'eleven', 10: 'ten'}, 'e'] + #. {10 : 'ten', 11 : 'eleven'} + #. {10 : 'ten', 11 : 'eleven', 'a' : ['a', 'b', 'c']} + #. (1, 2, 3, ['a', 'b', 'c']) + +Answer: ['a', 'b', 'c', {11: 'eleven', 10: 'ten'}, 'e'] + +8. Consider the python dictionary ``x = {'a' : ['a','b','c'], 'b' : + (1, 2, 3), 1 : {1 : 'one', 2 : 'two'}, 10 : {10 : 'ten', 11 : + 'eleven'}}``. The code ``(1, 2, 3) in x.values()`` will return + + a. True + #. False + #. Container-ship of values cannot be checked in dictionaries + #. The dictionary is invalid + +Answer: True + +Larger Questions +---------------- + +.. A minimum of 2 questions here (along with answers) + +1. Write a python script which can print the numbers from 1 to + 999(both included) in words. + +2. Given the list of marks of students in a class, write a program to + find the duplicate marks. List the duplicate marks and also print + the number of duplicates for each. + +3. Given a list of words, find the anagrams in it and list them. + [meats, tap, steep, tames, hare, pets, had, apt, teams, dark, + dealer, once, rhea, cloud, step, steam, have, could, ounce, pest, + head, leader, cone, rare, rear, hear, pat, mates] + diff -r 25b4e962b55e -r c7f0069d698a dictionaries/script.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/dictionaries/script.rst Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,177 @@ +.. 8.4 LO: dictionaries (2) +.. ------------------------ +.. * empty +.. * filled +.. * accessing via keys +.. * .values(), .keys() +.. * in +.. * iteration + +============ +Dictionaries +============ + +{{{ show the welcome slide }}} + +Welcome to the spoken tutorial on dictionaries. + +{{{ switch to next slide, outline slide }}} + +In this tutorial, we will see how to create empty dictionaries, learn +about keys and values of dictionaries. Checking for elements and +iterating over elements. + +{{{ switch to next slide on overview of dictionaries }}} + +A dictionary in general, is designed to look up meanings of +words. Similarly, Python dictionary is also designed to look up for a +specific key and retrieve the corresponding value. Dictionaries are +data structures that provide key-value mappings. Dictionaries are +similar to lists except that instead of the values having integer +indexes, dictionaries have keys or strings as indexes. + +Before we can proceed, start your IPython interpreter with the +``-pylab`` option. + +{{{ start ipython interpreter by issuing command ipython -pylab }}} + +Let us start by creating an empty dictionary, type the following in +your IPython interpreter. +:: + + mt_dict = {} + +Notice that unlike lists curly braces are used define ``dictionary``, + +{{{ move the mouse over curly braces to grab attention }}} + +Now let us see how to create a filled dictionary, +:: + + extensions = {'jpg' : 'JPEG Image', 'py' : 'Python script', 'html' : 'Html document', 'pdf' : 'Portable Document Format'} + +Notice that each key-value pair is separated by a comma + +{{{ move the mouse over the commas to grab attention }}} + +and each key and value are separated using a colon. + +{{{ move the mouse over the colon one by one to grab attention }}} + +Here, we defined four entries in the dictionary extensions. The keys +are + +{{{ spell the keys letter by letter }}} + +jpg, py, html, and pdf. + +Simply type, +:: + + extensions + +in the interpreter to see the content of the dictionary. Notice that +in dictionaries the order cannot be predicted and you can see that the +values are not in the order that we entered in. + +Like in lists, the elements in a dictionary can be accessed using the +index, here the index is the key. Try, +:: + + print extensions['jpg'] + +It printed JPEG Image. And now try, +:: + + print extensions['zip'] + +Well it gave us an error, saying that the key 'zip' is not in the +dictionary. + +Pause here for some time and try few more keys. Also try jpg in +capital letters. + +{{{ switch to next slide, adding and deleting keys and values in +dictionaries }}} + +Well that was about creating dictionaries, now how do we add or delete +items. We can add new items into dictionaries as, +:: + + extensions['cpp'] = 'C++ code' + +and delete items using the ``del`` keyword as, +:: + + del extension['pdf'] + +Let us check the content of the dictionary now, +:: + + extensions + +So the changes have been made. Now let us try one more thing, +:: + + extensions['cpp'] = 'C++ source code' + extensions + +As you can see, it did not add a new thing nor gave an error, but it +simply replaces the existing value with the new one. + +Now let us learn how to check if a particular key is present in the +dictionary. For that we can use ``in``, +:: + + 'py' in extensions + 'odt' in extensions + +So in short it will return ``True`` if the key is found in the +dictionary, and will return ``False`` if key is not present. Note that +we can check only for container-ship of keys in dictionaries and not +values. + +{{{ switch to next slide, Retrieve keys and values }}} + +Now let us see how to retrieve the keys and values. We can use the +method ``keys()`` for getting a list of the keys in a particular +dictionary and the method ``values()`` for getting a list of +values. Let us try them, +:: + + extensions.keys() + +It returned the ``list`` of keys in the dictionary extensions. And now +the other one, +:: + + extensions.values() + +It returned the ``list`` of values in the dictionary. + +{{{ switch to next slide, problem statement for the next solved +exercise }}} + +Now let us try to print the data in the dictionary. We can use ``for`` +loop to iterate. +:: + + for each in extensions.keys(): + print each, "-->", extensions[each] + + +{{{ switch to next slide, recap }}} + +This brings us to the end of this tutorial, we learned dictionaries +and saw how to create an empty dictionary, build a dictionary with +some data in it, adding data, ``keys()`` and ``values()`` methods, and +iterating over the dictionaries. + +{{{ switch to next slide, thank you slide }}} + +Thank you! + +.. Author: Anoop Jacob Thomas + Reviewer 1: + Reviewer 2: + External reviewer: diff -r 25b4e962b55e -r c7f0069d698a getting-started-with-arrays/questions.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/getting-started-with-arrays/questions.rst Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,132 @@ +Objective Questions +------------------- + +.. A mininum of 8 questions here (along with answers) + +1. An array in Python is the same as a Python list + + a. True + #. False + +Answer: False + +2. ``x = array([1, 2, 3], [5, 6, 7])`` is a valid statement + + a. True + #. False + +Answer: False + +3. What will be the output of the following code, + :: + + x = array([[1, 2, 3], ['a', 2, 'c']]) + print x[0][0] + x[0][1] + x[0][2] + + a. 6 + #. 123 + #. a2c + #. Error as array takes only homogeneous elements + +Answer: 123 + +4. What will be the output of the following code, + :: + + x = [[1, 2, 3], [4.1, 4.2, 4.3], ['6','7',8]] + y = array(x) + print y[-1][-2] + y[-1][-1] + y[-2][0] + y[0][-2] + + a. 21.1 + #. 12.5 + #. 784.12 + #. Error as array takes only homogeneous elements + + .. 4.2 4.3 2 2 + +Answer: 784.12 + +5. What is the output of the following code, + :: + + x = array([[1, 2, 3], ['a', 2, 'c']]) + identity(x.shape) + + a. Will create an identity matrix of shape (2, 3). + #. ``identity()`` function takes an integer as argument and a tuple + is passed. + #. Will return, array([[1,0,1],[0,1,0]]) + #. Will return, array([[0,1,0],[0,1,0]]) + +Answer: ``identity()`` function takes an integer as argument and a + tuple is passed. + +6. ``ones_like()`` function? + + (A) Returns an array of ones with the same shape and type as a + given array. + (B) Return a new array of given shape and type, filled with ones. + + Read the statements and answer, + + a. Only statement A is correct. + #. Only statement B is correct. + #. Both statement A and B are correct. + #. Both statement A and B are incorrect. + +Answer: Only statement A is correct. + +7. ``zeros_like()`` function? + + (A) Return a new array of given shape and type, filled with zeros. + (B) Returns an array of zeros with the same shape and type as a + given array. + + + Read the statements and answer, + + a. Only statement A is correct. + #. Only statement B is correct. + #. Both statement A and B are correct. + #. Both statement A and B are incorrect. + +Answer: Only statement B is correct. + +8. What will be output of the following code snippet. + :: + + x = linspace(1,10,10).reshape(5,2) + print (x[-3]+x[-4]).sum() + + a. 10.0 + #. 18.0 + #. 14.0 + #. 16.44 + #. Error + +Answer: 18 + +Larger Questions +---------------- + +.. A minimum of 2 questions here (along with answers) + +1. Write a python script to create a 15x15 array of equally spaced 225 + elements from 1 to 1000, add 5 to each of the diagonal elements and + find the sum of all odd rows of the array. Say for example the + array, + :: + + x = array([[1, 2, 3], + [4, 5, 6], + [7, 8, 9]]) + + will give answer 40 ((1+5) + 2 + 3 + 7 + 8 + (9+5)). + +2. For any given array([a1, a2, a3, .. , an]) the Vandermonde matrix + will be [[1, a1, a1**2, .. , a1**(n-1)], [1, a2, a2**2, .. , + a2**(n-1)], .. , [1, an, an**2, .. ,an**(n-1)]]. Write a python + script to generate the Vandermonde matrix and find the determinant + of the matrix for [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, + 16, 17, 18, 19, 20]. [Hint: to find the determinant use the + function ``det()`` from ``linalg`` module.] diff -r 25b4e962b55e -r c7f0069d698a getting-started-with-arrays/script.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/getting-started-with-arrays/script.rst Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,242 @@ +.. 4.1 LO: getting started with arrays (2) [anoop] +.. ------------------------------------------------ +.. * why arrays +.. + speed - simply say +.. + array level operations +.. * creating arrays +.. + direct data +.. + list conversion +.. + homogeneous +.. + builtins - identitiy, zeros, +.. * array operations +.. + =+ - * /= + +=========================== +Getting started with Arrays +=========================== + +{{{ show the welcome slide }}} + +Welcome to the spoken tutorial on getting started with arrays. + +{{{ switch to next slide, outline slide }}} + +In this tutorial, we will learn about arrays, how to convert a list +into an array and also why an array is preferred over lists. And array +operations. + +{{{ switch to next slide on overview of array }}} + +Arrays are homogeneous data structures, unlike lists, arrays cannot +have heterogeneous data elements, that is, it can have only one type +of data type, either all integers, or strings, or float, and not a +mix. + +Arrays are really fast in mathematical operations when compared to +lists, it is at least 80 to 100 times faster than lists. + +{{{ switch to the next slide, creating arrays }}} + +Now let us see how to create arrays. + +I am assuming that you have your IPython interpreter running with the +``-pylab`` option, so that you have the required modules loaded. + +To create an array we will use the function ``array()`` as, +:: + + a1 = array([1,2,3,4]) + +Notice that here we created a one dimensional array. Also notice the +object we passed to create an array. Now let us see how to create a +two dimensional array. Pause here and try to do it yourself before +looking at the solution. + +This is how we create two dimensional arrays. +:: + + a2 = array([[1,2,3,4],[5,6,7,8]]) + +Let us see an easy method of creating an array with elements 1 to 8. +:: + + ar = arange(1,9) + +And it created a single dimensional array of elements from 1 to 8. +:: + + print ar + +And how can we make it a two dimensional array of order 2 by 4. Pause +here and try to do it yourself, try ``ar.tab`` and find a suitable +method for that. + +We can use the function ``reshape()`` for that purpose and it can be +done as, +:: + + ar.reshape(2,4) + ar.reshape(4,2) + ar = ar.reshape(2,4) + +Now, let us see how to convert a list object to an array. As you have +already seen, in both of the previous statements we have passed a +list, so creating an array can be done so, first let us create a list +``l1`` +:: + + l1 = [1,2,3,4] + +Now we can convert the list to an array as, +:: + + a3 = array(l1) + + +{{{ switch to the next slide, problem statement of unsolved exercise 1 }}} + +Create a three dimensional array of the order (2,2,4). + +{{{ switch to the next slide, shape of an array }}} + +To find the shape of an array we can use the object ``.shape``, let us +check the shape of the arrays we have created so far, +:: + + a1.shape + +``a1.shape`` object is a tuple, and since a1 is a single dimensional +array, it returned a tuple (4,). + +{{{ switch to the next slide, unsolved exercise 2 }}} + +Find out the shape of the other two arrays that we have created. + +{{{ Array can have only a single type of data }}} + +Now let us try to create a new array with a mix of elements and see +what will happen, +:: + + a4 = array([1,2,3,'a string']) + +Well, we expected an error as previously I said that an array can have +only homogeneous elements, but it didn't give an error. Let us check +the values in the new array created. In your IPython terminal type, +:: + + a4 + +Did you notice it, + +{{{ highlight all the array elements one by one using mouse +movements }}} + +all the elements have been implicitly type casted as string, though +our first three elements were integers. + +{{{ switch to the next slide, identity & zeros methods }}} + +An identity matrix is a square matrix in which all the diagonal +elements are one and rest of the elements zero. We can create an +identity matrix using the method ``identity()``. + +The function ``identity()`` takes an integer argument, +:: + + identity(3) + +As you can see the identity method returned a three by three square +array with all the diagonal elements as one and the rest of the +elements as zero. + +``zeros()`` function accepts a tuple, which is the order of the array +we want to create, and it generates an array with all elements zero. + +{{{ switch to the next slide, problem statement of the solved exercise +1 }}} + +Let us creates an array of the order four by five with all the +elements zero. We can do it using the method zeros, +:: + + zeros((4,5)) + +Notice that we passed a tuple to the function zeros. + +{{{ switch to next slide, learning exercise }}} + +We learned two functions ``identity()`` and ``zeros()``, find out more +about the functions ``zeros_like()``, ``ones()``, ``ones_like()``. + +{{{ switch to next slide, array operations }}} + +Try the following, first check the value of a1, +:: + + a1 + +``a1`` is a single dimensional array, and now try, +:: + + a1 * 2 + +It returned a new array with all the elements multiplied by 2. +:: + + a1 + +note that the value of a1 still remains the same. + +Similarly with addition, +:: + + a1 + 2 + +it returns a new array, with all the elements summed with two. But +again notice that the value of a1 has not been changed. +:: + + a1 + +You may change the value of a1 by simply assigning the newly returned +array as, +:: + + a1 += 2 + +Notice the change in elements of a, +:: + + a + +We can use all the mathematical operations with arrays, Now let us try +this +:: + + a1 = array([1,2,3,4]) + a2 = array([1,2,3,4]) + a1 + a2 + +Returns an array with element by element addition, +:: + + a1 * a2 + +Returns an array with element by element multiplication, notice that +it does not perform matrix multiplication. + +{{{ switch to next slide, recap slide }}} + +So this brings us to the end of this tutorial, in this tutorial we +covered basics of arrays, how to create an array, converting a list to +an array, basic array operations etc. + +{{{ switch to next slide, thank you }}} + +Thank you! + +.. Author: Anoop Jacob Thomas + Reviewer 1: + Reviewer 2: + External reviewer: diff -r 25b4e962b55e -r c7f0069d698a getting-started-with-for/questions.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/getting-started-with-for/questions.rst Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,115 @@ +Objective Questions +------------------- + +.. A mininum of 8 questions here (along with answers) + +1. In Python a block is represented by + + a. Curly braces + #. Begin and End keywords + #. Indentation + #. Curly braces + Indentation + #. All of the above + +Answer: Indentation + +2. Indentation is not mandatory in Python + + a. True + #. False + +Answer: False + +3. A ``for`` loop in Python, + + a. is a simple iterator + #. is a condition based loop + #. can iterate only over integer list of elements + #. All of the above + +Answer: is a simple iterator + +4. ``range()`` function can generate negative numbers + + a. True + #. False + +Answer: True + +5. ``range(a,b)`` function returns, + + a. A tuple of elements from a to b including a and b + #. A tuple of elements from a to b excluding b + #. A list of elements from a to b including a and b + #. A list of elements from a to b excluding b + +Answer: A list of elements from a to b excluding b + +6. ``linspace(1,100,2)`` and ``range(1,100,2)`` produces the same output, + + a. True + #. False + +Answer: False + +7. What is the output of the below code snippet? + :: + + y = 1 + for x in range(21): + y*=x + print y + + a. Product of natural numbers up to 20(including) + #. Product of natural numbers up to 21(including) + #. Zero + #. Error + +Answer: Zero + +8. What is the output of the below code snippet? + :: + + y = 1 + for x in range(1,21): + y*=x + print y + + a. Product of natural numbers up to 20(including) + #. Product of natural numbers up to 21(including) + #. Zero + #. Error + +Answer: Product of natural numbers up to 20(including) + +9. What is the output of the below code snippet? + :: + + y = 1 + for x in range(1,21) + y*=x + print y + + a. Product of natural numbers up to 20(including) + #. Product of natural numbers up to 21(including) + #. Zero + #. Error + +Answer: Error + +Larger Questions +---------------- + +.. A minimum of 2 questions here (along with answers) + +1. Write a python script to calculate the sum of the first 1000 + natural numbers? + +2. Write a python script to find out prime numbers up to 500. + [`hint`: a number ``A`` which is divisible by only ``1`` and ``A`` + is a prime number.] + +3. Write a python script to find out the difference between the + square of sum of first 100 natural numbers and sum of squares of + first 100 natural numbers. + diff -r 25b4e962b55e -r c7f0069d698a getting-started-with-for/script.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/getting-started-with-for/script.rst Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,273 @@ +.. 3.2 LO: getting started with =for= (2) [anoop] +.. ----------------------------------------------- +.. * blocks in python +.. + (indentation) +.. * blocks in ipython +.. + ... prompt +.. + hitting enter +.. * =for= with a list +.. * =range= function + +============================= +Getting started with for loop +============================= + +{{{ show welcome slide }}} + +Hello and welcome to the tutorial getting started with ``for`` loop. + +{{{ switch to next slide, outline slide }}} + +In this tutorial we will learn about ``for`` loops in python, and also +learn how to write blocks of code in Python. + +.. #[Nishanth]: Instead of saying basics of indenting code, + say How to define code blocks in Python + +{{{ switch to next slide, about whitespaces }}} + +In Python whitespace is significant, and the blocks are visually +separated. + +.. #[nishanth]: Simply tell how blocks are defined in python. + The details like braces are not used and its + advantages like neat code can be told after completely + explaining the indentation + +.. #[Amit]: Do you want to do that here. May be its better to talk about + this after some initiation into the idea of blocks. + +The best practice is to indent the code using four spaces. + +.. #[Nishanth]: Even this detail may be skipped. Simply say use 4 spaces + for indentation. Do that while typing so that they can + actually see what is being typed. + +Now let us move straight into ``for`` loop. + +{{{ switch to next slide, problem statement of exercise 1 }}} + + +Write a for loop which iterates through a list of numbers and find the +square root of each number. +:: + + numbers are 1369, 7225, 3364, 7056, 5625, 729, 7056, 576, 2916 + +.. #[nishanth]: making new list with square roots induces extra complication + like appending which has no use case here + +.. #[Nishanth]: The problem focuses more on square root and creation + of list. The problem must be simple and focusing on + nothing more but the indentation and for loop. + May be change the problem to print squares than to + print square roots. + +For the problem, first we need to create a ``list`` of numbers and +then iterate over the list and find the square root of each element in +it. And let us create a script, rather than typing it out in the +interpreter itself. Create a script called list_roots.py and type the +following. + +{{{ open the text editor and paste the following code there }}} +:: + + numbers = [1369, 7225, 3364, 7056, 5625, 729, 7056, 576, 2916] + for each in numbers: + print "Square root of", each, "is", sqrt(each) + print "This is not in for loop!" + +.. numbers = [1, 12, 3, 4, 21, 17] + for each in numbers: + print each, each * each + +.. #[nishanth]: I don't see a use case to append the sq_root to + square_roots. It is only complicating stuff. + Simply iterate and print. + +{{{ save the script }}} + +Now save the script, and run it from your IPython interpreter. I +assume that you have started your IPython interpreter using ``-pylab`` +option. + +Run the script as, +:: + + %run -i list_roots.py + +.. #[Nishanth]: you don't have to use the -i option here + +{{{ run the script }}} + +So that was easy! All what we did was iterate over the list element by +element and then use the element for calculation. Note that here we +used two variables. One the variable ``numbers``, which is a list, +another one ``each``, which is the element of list under consideration +in each cycle of the ``for`` loop. The variable names can be chosen by +you. + +.. #[Nishanth]: The details like we didn't have to find the length + are relevant for people who have programmed in C or + other languages earlier. But for a newbie it is more + of confusing extra info. That part may be skipped. + Simply go ahead and focus on the syntax of for loop. + And how the variable name is used inside the for loop. + If you modify the question to only print, the extra + variable sq_root can also be avoided. let it be more + about "each", "numbers" and "for". no other new names. + +{{{ show the script which was created }}} + +Note that the lines after ``for`` statement, is indented using four +spaces. + +{{{ highlight the line after for statement }}} + +It means that line is part of the for loop. And it is a block of code, +although it is only a single statement in the block. And the fourth +line or the immediate line after the ``for`` block is not indented, + +{{{ highlight the fourth line - the line just after for loop }}} + +it means that it is not part of the ``for`` loop and the lines after +that doesn't fall in the scope of the ``for`` loop. Thus each block is +separated by the indentation level. Thus marking the importance of +white-spaces in Python. + +{{{ switch to the slide which shows the problem statement of the first +problem to be tried out }}} + +Now a question for you to try, from the given numbers make a list of +perfect squares and a list of those which are not. The numbers are, +:: + + 7225, 3268, 3364, 2966, 7056, 5625, 729, 5547, 7056, 576, 2916 + +{{{ switch to next slide, problem statement of second problem in +solved exercise}}} + +Now let us try a simple one, to print the square root of numbers in +the list. And this time let us do it right in the IPython +interpreter. + +{{{ switch focus to the IPython interpreter }}} + +So let us start with making a list. Type the following +:: + + numbers = [1369, 7225, 3364, 7056, 5625, 729, 7056, 576, 2916] + for each in numbers: + +and now you will notice that, as soon as you press the return key +after for statement, the prompt changes to four dots and the cursor is +not right after the four dots but there are four spaces from the +dots. Please note that IPython automatically indents the block. The +four dots tell you that you are inside a block. Now type the rest of +the ``for`` loop, + +.. #[Nishanth]: Tell that IPython does auto indentation. + +:: + + print "Square root of", each, "is", sqrt(each) + +Now we have finished the statements in the block, and still the +interpreter is showing four dots, which means you are still inside the +block. To exit from the block press return key or the enter key twice +without entering anything else. It printed the square root of each +number in the list, and that is executed in a ``for`` loop. + +Now, let us find the cube of all the numbers from one to ten. But this +time let us try it in the vanilla version of Python interpreter. + +Start the vanilla version of Python interpreter by issuing the command +``python`` in your terminal. + +{{{ open the python interpreter in the terminal using the command +python to start the vanilla Python interpreter }}} + +Start with, +:: + + for i in range(1,11): + +and press enter once, and we will see that this time it shows four +dots, but the cursor is close to the dots, so we have to indent the +block. The vanilla version of Python interpreter does not indent the +code automatically. So enter four spaces there and then type the +following +:: + + print i, "cube is", i**3 + +Now when we hit enter, we still see the four dots, to get out of the +block, hit enter once again + +.. #[Nishanth]: Here also the overhead on print can be reduced. + Think of a simple print statement. This statement + will be confusing for a newbie. + We can focus more on indentation in python. + +.. #[nishanth]: Not sure if you must use range here. You can + define a list of numbers and iterate on it. + Then say this list can also be generated using + the range function and hence introduce range. + +Okay! so the main thing here we learned is how to use Python +interpreter and IPython interpreter to specify blocks. But while we +were generating the multiplication table we used something new, +``range()`` function. ``range()`` is an inbuilt function in Python +which can be used to generate a ``list`` of integers from a starting +number to an ending number. Note that the ending number that you +specify will not be included in the ``list``. + +.. #[Nishanth]: Show some examples of range without the step argument + May be give an exercise with negative numbers as arguments + +Now, let us print all the odd numbers from 1 to 50. Let us do it in +our IPython interpreter for ease of use. + +{{{ switch to next slide, problem statement of the next problem in +solved exercises }}} + +{{{ switch focus to ipython interpreter }}} + +The problem can be solved by just using the ``range()`` function. + +It can be solved as, +:: + + print range(1,51,2) + +This time we passed three parameters to ``range()`` function unlike +the previous case where we passed only two parameters. The first two +parameters are the same in both the cases. The first parameter is the +starting number of the sequence and the second parameter is the end of +the range. Note that the sequence doesn't include the ending +number. The third parameter is for stepping through the sequence. Here +we gave two which means we are skipping every alternate element. + +{{{ switch to next slide, recap slide }}} + +Thus we come to the end of this tutorial. We learned about blocks in +Python, indentation, blocks in IPython, for loop, iterating over a +list and then the ``range()`` function. + +.. #[Amit]: There does seem to too much overhead of details. Should + the first example be done using script is it necessary. + Do add some things in evolutionary manner. Like introducing + range as a list and doing a very very simple for loop.Like + iterating over [1,2,3] .Before getting into a problem. + And club details about problem in one paragraph and syntactic details + in other. + +{{{ switch to next slide, thank you slide }}} + +Thank you! + +.. Author: Anoop Jacob Thomas + Reviewer 1: Nishanth + Reviewer 2: Amit Sethi + External reviewer: + diff -r 25b4e962b55e -r c7f0069d698a matrices/questions.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/matrices/questions.rst Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,32 @@ +Objective Questions +------------------- + +.. A mininum of 8 questions here (along with answers) + + +Larger Questions +---------------- + +.. A minimum of 2 questions here (along with answers) + +1. Consider an array [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. A fold and add + operation consist of two phases, a right fold and add and a left + fold and add. + + Say in first fold and add, we take the right fold of the array and + add it to the left like, + + [1+10, 2+9, 3+8, 4+7, 5+6, 6, 7, 8, 9, 10] + + and it becomes + + [11, 11, 11, 11, 11, 6, 7, 8, 9, 10] + + and in the second fold and add, we take the left fold of the new + array and add it to the right and it becomes, + + [11, 11, 11, 11, 11, 17, 18, 19, 20, 21]. + + What will be the array after 22 such operations starting with [1, + 2, 3, 4, 5, 6, 7, 8, 9, 10] + diff -r 25b4e962b55e -r c7f0069d698a matrices/script.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/matrices/script.rst Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,265 @@ +.. 4.3 LO: Matrices (3) [anoop] +.. ----------------------------- +.. * creating matrices +.. + direct data +.. + list conversion +.. + builtins - identitiy, zeros, +.. * matrix operations +.. + + - * / +.. + dot +.. + inv +.. + det +.. + eig +.. + norm +.. + svd + +======== +Matrices +======== +{{{ show the welcome slide }}} + +Welcome to the spoken tutorial on Matrices. + +{{{ switch to next slide, outline slide }}} + +In this tutorial we will learn about matrices, creating matrices and +matrix operations. + +{{{ creating a matrix }}} + +All matrix operations are done using arrays. Thus all the operations +on arrays are valid on matrices also. A matrix may be created as, +:: + + m1 = matrix([1,2,3,4]) + +Using the tuple ``m1.shape`` we can find out the shape or size of the +matrix, +:: + + m1.shape + +Since it is a one row four column matrix it returned a tuple, one by +four. + +A list can be converted to a matrix as follows, +:: + + l1 = [[1,2,3,4],[5,6,7,8]] + m2 = matrix(l1) + +Note that all matrix operations are done using arrays, so a matrix may +also be created as +:: + + m3 = array([[5,6,7,8],[9,10,11,12]]) + +{{{ switch to next slide, matrix operations }}} + +We can do matrix addition and subtraction as, +:: + + m3 + m2 + +does element by element addition, thus matrix addition. + +Similarly, +:: + + m3 - m2 + +it does matrix subtraction, that is element by element +subtraction. Now let us try, +:: + + m3 * m2 + +Note that in arrays ``array(A) star array(B)`` does element wise +multiplication and not matrix multiplication, but unlike arrays, the +operation ``matrix(A) star matrix(B)`` does matrix multiplication and +not element wise multiplication. And in this case since the sizes are +not compatible for multiplication it returned an error. + +And element wise multiplication in matrices are done using the +function ``multiply()`` +:: + + multiply(m3,m2) + +Now let us see an example for matrix multiplication. For doing matrix +multiplication we need to have two matrices of the order n by m and m +by r and the resulting matrix will be of the order n by r. Thus let us +first create two matrices which are compatible for multiplication. +:: + + m1.shape + +matrix m1 is of the shape one by four, let us create another one of +the order four by two, +:: + + m4 = matrix([[1,2],[3,4],[5,6],[7,8]]) + m1 * m4 + +thus unlike in array object ``star`` can be used for matrix multiplication +in matrix object. + +{{{ switch to next slide, recall from arrays }}} + +As we already saw in arrays, the functions ``identity()``, +``zeros()``, ``zeros_like()``, ``ones()``, ``ones_like()`` may also be +used with matrices. + +{{{ switch to next slide, matrix operations }}} + +To find out the transpose of a matrix we can do, +:: + + print m4 + m4.T + +Matrix name dot capital T will give the transpose of a matrix + +{{{ switch to next slide, Euclidean norm of inverse of matrix }}} + +Now let us try to find out the Euclidean norm of inverse of a 4 by 4 +matrix, the matrix being, +:: + + m5 = matrix(arange(1,17).reshape(4,4)) + print m5 + +The inverse of a matrix A, A raise to minus one is also called the +reciprocal matrix such that A multiplied by A inverse will give 1. The +Euclidean norm or the Frobenius norm of a matrix is defined as square +root of sum of squares of elements in the matrix. Pause here and try +to solve the problem yourself, the inverse of a matrix can be found +using the function ``inv(A)``. + +And here is the solution, first let us find the inverse of matrix m5. +:: + + im5 = inv(m5) + +And the euclidean norm of the matrix ``im5`` can be found out as, +:: + + sum = 0 + for each in array(im5.flatten())[0]: + sum += each * each + print sqrt(sum) + +{{{ switch to next slide, infinity norm }}} + +Now try to find out the infinity norm of the matrix im5. The infinity +norm of a matrix is defined as the maximum value of sum of the +absolute of elements in each row. Pause here and try to solve the +problem yourself. + +The solution for the problem is, +:: + + sum_rows = [] + for i in im5: + sum_rows.append(abs(i).sum()) + print max(sum_rows) + +{{{ switch to slide the ``norm()`` method }}} + +Well! to find the Euclidean norm and Infinity norm we have an even easier +method, and let us see that now. + +The norm of a matrix can be found out using the method +``norm()``. Inorder to find out the Euclidean norm of the matrix im5, +we do, +:: + + norm(im5) + +And to find out the Infinity norm of the matrix im5, we do, +:: + + norm(im5,ord=inf) + +This is easier when compared to the code we wrote. Do ``norm`` +question mark to read up more about ord and the possible type of norms +the norm function produces. + +{{{ switch to next slide, determinant }}} + +Now let us find out the determinant of a the matrix m5. + +The determinant of a square matrix can be obtained using the function +``det()`` and the determinant of m5 can be found out as, +:: + + det(m5) + +{{{ switch to next slide, eigen vectors and eigen values }}} + +The eigen values and eigen vector of a square matrix can be computed +using the function ``eig()`` and ``eigvals()``. + +Let us find out the eigen values and eigen vectors of the matrix +m5. We can do it as, +:: + + eig(m5) + +Note that it returned a tuple of two matrices. The first element in +the tuple are the eigen values and the second element in the tuple are +the eigen vectors. Thus the eigen values are, +:: + + eig(m5)[0] + +and the eigen vectors are, +:: + + eig(m5)[1] + +The eigen values can also be computed using the function ``eigvals()`` as, +:: + + eigvals(m5) + +{{{ switch to next slide, singular value decomposition }}} + +Now let us learn how to do the singular value decomposition or S V D +of a matrix. + +Suppose M is an m×n matrix whose entries come from the field K, which +is either the field of real numbers or the field of complex +numbers. Then there exists a factorization of the form + + M = U\Sigma V star + +where U is an (m by m) unitary matrix over K, the matrix \Sigma is an +(m by n) diagonal matrix with nonnegative real numbers on the +diagonal, and V*, an (n by n) unitary matrix over K, denotes the +conjugate transpose of V. Such a factorization is called the +singular-value decomposition of M. + +The SVD of matrix m5 can be found as +:: + + svd(m5) + +Notice that it returned a tuple of 3 elements. The first one U the +next one Sigma and the third one V star. + +{{{ switch to next slide, recap slide }}} + +So this brings us to the end of this tutorial. In this tutorial, we +learned about matrices, creating matrices, matrix operations, inverse +of matrices, determinant, norm, eigen values and vectors and singular +value decomposition of matrices. + +{{{ switch to next slide, thank you }}} + +Thank you! + +.. Author: Anoop Jacob Thomas + Reviewer 1: + Reviewer 2: + External reviewer: diff -r 25b4e962b55e -r c7f0069d698a other-type-of-plots/script.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/other-type-of-plots/script.rst Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,220 @@ +.. 2.4 LO: other types of plots (3) [anoop] +.. ----------------------------------------- +.. * scatter +.. * pie chart +.. * bar chart +.. * log +.. * illustration of other plots, matplotlib help + +=================== +Other type of plots +=================== + +{{{ show the first slide }}} + +Hello and welcome to the tutorial other type of plots. + +{{{ show the outline slide }}} + +In this tutorial we will cover scatter plot, pie chart, bar chart and +log plot. We will also see few other plots and also introduce you to +the matplotlib help. + + +Let us start with scatter plot. + +{{{ switch to the next slide }}} + +In a scatter plot, the data is displayed as a collection of points, +each having the value of one variable determining the position on the +horizontal axis and the value of the other variable determining the +position on the vertical axis. This kind of plot is also called a +scatter chart, scatter diagram and scatter graph. + +Before we proceed further get your IPython interpreter running with +the ``-pylab`` option. Start your IPython interpreter as +:: + + ipython -pylab + +{{{ open the ipython interpreter in the terminal using the command +ipython -pylab }}} + +{{{ switch to the next slide having the problem statement of first +exercise }}} + +Now, let us plot a scatter plot showing the percentage profit of company A +from the year 2000-2010. The data for the same is available in the +file ``company-a-data.txt``. + +{{{ open the file company-a-data.txt and show the content }}} + +The data file has two lines with a set of values in each line, the +first line representing years and the second line representing the +profit percentages. + +{{{ close the file and switch to the terminal }}} + +To product the scatter plot first we need to load the data from the +file using ``loadtxt``. We learned in one of the previous sessions, +and it can be done as :: + + year,profit = loadtxt('/home/fossee/other-plot/company-a-data.txt',dtype=type(int())) + +Now in-order to generate the scatter graph we will use the function +``scatter()`` +:: + + scatter(year,profit) + +Notice that we passed two arguments to ``scatter()`` function, first +one the values in x-coordinate, year, and the other the values in +y-coordinate, the profit percentage. + +{{{ switch to the next slide which has the problem statement of +problem to be tried out }}} + +Now here is a question for you to try out, plot the same data with red +diamonds. + +**Clue** - *try scatter? in your ipython interpreter* + +.. scatter(year,profit,color='r',marker='d') + +Now let us move on to pie chart. + +{{{ switch to the slide which says about pie chart }}} + +A pie chart or a circle graph is a circular chart divided into +sectors, illustrating proportion. + +{{{ switch to the slide showing the problem statement of second +exercise question }}} + +Plot a pie chart representing the profit percentage of company A, with +the same data from file ``company-a-data.txt``. So let us reuse the +data we have loaded from the file previously. + +We can plot the pie chart using the function ``pie()``. +:: + + pie(profit,labels=year) + +Notice that we passed two arguments to the function ``pie()``. The +first one the values and the next one the set of labels to be used in +the pie chart. + +{{{ switch to the next slide which has the problem statement of +problem to be tried out }}} + +Now here is a question for you to try out, plot a pie chart with the +same data with colors for each wedges as white, red, black, magenta, +yellow, blue, green, cyan, yellow, magenta and blue respectively. + +**Clue** - *try pie? in your ipython interpreter* + +.. pie(t,labels=s,colors=('w','r','k','m','y','b','g','c','y','m','b')) + +{{{ switch to the slide which says about bar chart }}} + +Now let us move on to bar chart. A bar chart or bar graph is a chart +with rectangular bars with lengths proportional to the values that +they represent. + +{{{ switch to the slide showing the problem statement of third +exercise question }}} + +Plot a bar chart representing the profit percentage of company A, with +the same data from file ``company-a-data.txt``. + +So let us reuse the data we have loaded from the file previously. + +We can plot the bar chart using the function ``bar()``. +:: + + bar(year,profit) + +Note that the function ``bar()`` needs at least two arguments one the +values in x-coordinate and the other values in y-coordinate which is +used to determine the height of the bars. + +{{{ switch to the next slide which has the problem statement of +problem to be tried out }}} + +Now here is a question for you to try, plot a bar chart which is not +filled and which is hatched with 45\ :sup:`o` slanting lines as shown +in the image in the slide. + +**Clue** - *try bar? in your ipython interpreter* + +.. bar(year,profit,fill=False,hatch='/') + +{{{ switch to the slide which says about bar chart }}} + +Now let us move on to log-log plot. A log-log graph or log-log plot is +a two-dimensional graph of numerical data that uses logarithmic scales +on both the horizontal and vertical axes. Because of the nonlinear +scaling of the axes, a function of the form y = ax\ :sup:`b` will +appear as a straight line on a log-log graph + +{{{ switch to the slide showing the problem statement of fourth +exercise question }}} + + +Plot a `log-log` chart of y=5*x\ :sup:`3` for x from 1-20. + +Before we actually plot let us calculate the points needed for +that. And it could be done as, +:: + + x = linspace(1,20,100) + y = 5*x**3 + +Now we can plot the log-log chart using ``loglog()`` function, +:: + + loglog(x,y) + +To understand the difference between a normal ``plot`` and a ``log-log +plot`` let us create another plot using the function ``plot``. +:: + + figure(2) + plot(x,y) + +{{{ show both the plots side by side }}} + +So that was ``log-log() plot``. + +{{{ switch to the next slide which says: "How to get help on +matplotlib online"}}} + +Now we will see few more plots and also see how to access help of +matplotlib over the internet. + +Help about matplotlib can be obtained from +matplotlib.sourceforge.net/contents.html + +.. #[[Anoop: I am not so sure how to do the rest of it, so I guess we + can just browse through the side and tell them few. What is your + opinion??]] + +Now let us see few plots from +matplotlib.sourceforge.net/users/screenshots.html + +{{{ browse through the site quickly }}} + +{{{ switch to recap slide }}} + +Now we have come to the end of this tutorial. We have covered scatter +plot, pie chart, bar chart, log-log plot and also saw few other plots +and covered how to access the matplotlib online help. + +{{{ switch to the thank you slide }}} + +Thank you! + +.. Author: Anoop Jacob Thomas + Reviewer 1: + Reviewer 2: + External reviewer: diff -r 25b4e962b55e -r c7f0069d698a savefig/questions.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/savefig/questions.rst Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,118 @@ +Objective Questions +------------------- + +.. A mininum of 8 questions here (along with answers) + + +1. What argument can be used with savefig to increase the resolution + of the plot while saving a plot. + + a. fname + #. transparency + #. dpi + #. format + +Answer: dpi + +2. The fname argument of savefig has to be always absolute path. + + a. True + #. False + +Answer: False + +3. You are right now in the directory `/home/fossee`, from the + following which one is the correct one in-order to save the plot as + svg with the filename `plot` to the directory `/home/fossee/sine/` + + a. savefig('/sine/plot.svg') + #. savefig('sine/plot.svg') + #. savefig('home/fossee/sine/plot.svg') + #. All of these + #. None of the above + +Answer: savefig('sine/plot.svg') + +4. Which is the best image format to be used with Latex documents + which savefig supports? + + a. SVG - Scalable Vector Graphics + #. EPS - Encapsulated Post Script + #. PS - Post Script + #. PNG - Portable Network Graphics + #. None of the above + +Answer: EPS - Encapsulated Post Script + +5. ``savefig('sine.png')`` saves the plot in, + + a. The root directory ``/`` (on GNU/Linux, Unix based systems) + ``c:\`` (on windows). + #. Will result in an error as full path is not supplied. + #. The current working directory. + #. Predefined directory like ``/documents``. + +Answer: The current working directory. + +6. Study the following code and tell what will happen, + :: + savefig('cosine.png',facecolor='blue') + + a. Will generate an error as plot statements are missing + #. Will generate an error as full path is not specified + #. Create a file ``cosine.png`` with blue background at the current + working directory. + #. Create a file ``cosine.png`` with blue background at a + predefined directory like ``/documents``. + +Answer: Create a file ``cosine.png`` with blue background at the + current working directory. + +7. How to save the below plot as ``sine_green_border.png`` with green + color border/edge in the current working directory. The plot is given + as, + :: + x = linspace(-5*pi,5*pi,200) + plot(x,sin(x),linewidth=2) + legend(['sin(x)']) + + a. ``savefig('sine_green_border.png',bordercolor='green')`` + #. ``savefig('sine_green_border.png',facecolor='green')`` + #. ``savefig('sine_green_border.png',edgecolor='green')`` + #. ``savefig('/sine_green_border.png',bordercolor='green')`` + +Answer: savefig('sine_green_border.png',edgecolor='green') + +8. Given the below code snippet, what does it do? + :: + x = linspace(-5*pi,5*pi,200) + plot(x,sin(x),linewidth=2) + legend(['sin(x)']) + savefig('sine.png',format='pdf',papertype='a4') + + a. Save the sine plot in file sine.png as a pdf file in page-size + A4 and saves it into the current working directory + #. Save the sine plot in file sine.png.pdf in page-size A4 into the + current working directory. + #. Save the sine plot in a file sine.png in png format with + page-size A4 in the current working directory overriding the + format argument + #. Error in filename and format mismatch. + +Answer: Save the sine plot in file sine.png as a pdf file in page-size + A4 and saves it into the current working directory + +Larger Questions +---------------- + +.. A minimum of 2 questions here (along with answers) + +1. Plot a cosine plot from -2pi to 2pi in green color taking 300 + points. Title the plot as 'Cosine plot' and the legend plot with + 'cos(x)'. And save the plot as a pdf file with the filename + cosine_plot. + +2. Plot tan(x) where x varies from -4pi to 4pi in red color taking 600 + points. Title the plot as 'Tan plot' and the legend plot with + 'tan(x)'. And save the plot as a svg file with the filename + tangent_plot. diff -r 25b4e962b55e -r c7f0069d698a savefig/script.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/savefig/script.rst Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,118 @@ +.. 2.5 LO: saving plots (2) +.. ------------------------- +.. * Outline +.. + basic savefig +.. + png, pdf, ps, eps, svg +.. + going to OS and looking at the file + +======= +Savefig +======= + +Hello and welcome to the tutorial. In this tutorial you will learn how +to save plots using Python. + +Start your IPython interpreter with the command :: + + ipython -pylab + +It will start your IPython interpreter with the required python +modules for plotting and saving your plots. + +{{{ Open ipython }}} + +Now let us plot something, let us plot a sine wave from minus 3 pi to +3 pi. Let us start by calculating the required points for the plot. It +can be done using linspace as, :: + + x = linspace(-3*pi,3*pi,100) + +We have stored required points in x. Now let us plot the points using +the statement :: + + plot(x,sin(x)) + +{{{ Keep the plot open }}} + +Done! we have made a very basic sine plot, now let us see how to save +the plot for future use so that you can embed the plot in your +reports. + +{{{ Switch the focus to IPython interpreter window }}} + +For saving the plot, we will use savefig function, and it has to be +done with the plot window open. The statement is, :: + + savefig('/home/fossee/sine.png') + +Notice that ``savefig`` function takes one argument which is a string +which is the filename. The last 3 characters after the ``.`` in the +filename is the extension or type of the file which determines the +format in which you want to save. + +{{{ Highlight the /home/fossee part using mouse movements }}} + +Also, note that we gave the full path or the absolute path to which we +want to save the file. + +{{{ Highlight the .png part using mouse movements }}} + +Here I have used an extension ``.png`` which means i want to save the +image as a PNG file. + +Now let us locate ``sine.png`` file saved. We saved the file to +``/home/fossee`` so let us navigate to ``/home/fossee`` using the +file browser. + +{{{ Open the browser, navigate to /home/fossee and highlight the file +sine.png }}} + +Yes, the file ``sine.png`` is here and let us check it. + +{{{ Open the file sine.png and show it for two-three seconds and then +close it and return to IPython interpreter, make sure the plot window +is still open, also don't close the file browser window }}} + +So in-order to save a plot, we use ``savefig`` function. ``savefig`` +can save the plot in many formats, such as pdf - portable document +format, ps - post script, eps - encapsulated post script, svg - +scalable vector graphics, png - portable network graphics which +support transparency etc. + +.. #[[slide must give the extensions for the files - Anoop]] + +Let us now try to save the plot in eps format. ``eps`` stands for +encapsulated post script, and it can be embedded in your latex +documents. + +{{{ Switch focus to the already open plot window }}} + +We still have the sine plot with us, and now let us save the plot as +``sine.eps``. + +{{{ Switch focus to IPython interpreter }}} + +Now, We will save the plot using the function ``savefig`` :: + + savefig('/home/fossee/sine.eps') + +{{{ Switch focus to file browser window }}} + +Now let us go to ``/home/fossee`` and see the new file created. + +{{{ Highlight the file sine.eps with a single mouse click for 2 +seconds and then double click and open the file }}} + +Yes! the new file ``sine.eps`` is here. + +Now you may try saving the same in pdf, ps, svg formats. + +Let us review what we have learned in this session! We have learned to +save plots in different formats using the function ``savefig()``. + +Thank you! + +.. Author: Anoop Jacob Thomas + Reviewer 1: + Reviewer 2: + External reviewer: diff -r 25b4e962b55e -r c7f0069d698a using python modules/four_plot.png Binary file using python modules/four_plot.png has changed diff -r 25b4e962b55e -r c7f0069d698a using python modules/four_plot.py --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/using python modules/four_plot.py Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,11 @@ +x=linspace(-5*pi, 5*pi, 500) +plot(x, x, 'b') +plot(x, -x, 'b') +plot(x, sin(x), 'g', linewidth=2) +plot(x, x*sin(x), 'r', linewidth=3) +legend(['x', '-x', 'sin(x)', 'xsin(x)']) +annotate('origin', xy = (0, 0)) +title('Four Plot') +xlim(-5*pi, 5*pi) +ylim(-5*pi, 5*pi) +#show() diff -r 25b4e962b55e -r c7f0069d698a using python modules/questions.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/using python modules/questions.rst Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,120 @@ +Objective Questions +------------------- + +.. A mininum of 8 questions here (along with answers) + +1. What will be output of the following code snippet, + :: + + from math import sqrt + + def sqrt(i): + return i + + print sqrt(49) + + a. 7.0 + #. 7 + #. 49 + #. 49.0 + #. Error + +Answer: 49 + +2. What will be the output of the following code snippet, + :: + + import math + + def sqrt(i): + x = math.sqrt(i) + if int(x) == x: + return int(x) + else: + return x + + print math.sqrt(50), sqrt(50), math.sqrt(49), sqrt(49) + + a. 7.0710678118654755 7 7 7 + #. 7.0710678118654755 7 7.0 7 + #. 7 7 7 7 + #. 7.0710678118654755 7.0710678118654755 7.0 7 + +Answer: 7.0710678118654755, 7.0710678118654755, 7.0, 7 + +3. ``from math import *`` and ``import math`` does the same, + + a. True + #. False + +Answer: False + +4. Which among these libraries is part of python standard library, + + a. Mayavi + #. scipy + #. matplotlib + #. urllib2 + +Answer: urllib2 + +5. ``pylab.plot(x,sin(x))`` can be used in a script with ``from pylab + import *`` + + a. True + #. False + +Answer: False + +6. Which among this is correct, + + a. from scipy import plot + #. from numpy import plot + #. from matplotlib import plot + #. from pylab import plot + #. None of the above + +Answer: from pylab import plot + +7. Functions ``xlim()`` and ``ylim()`` can be imported to the current + name-space as, + + a. from pylab import xlim, ylim + #. import pylab + #. from scipy import xlim, ylim + #. import scipy + +Answer: from pylab import xlim, ylim + +8. ``scipy.linspace(-5*scipy.pi, 5*scipy.pi, 500)`` + + a. creates an array of 500 equally spaced elements from -5*scipy.pi + to 5*scipy.pi(excluded) + #. creates an array of 500 equally spaced elements from + -5*scipy.pi(excluded) to 5*scipy.pi(included) + #. creates an array of 500 equally spaced elements from -5*scipy.pi + to 5*scipy.pi, both end points included + #. created an array of 500 equally spaced elements from -5*scipy.pi + to 5*scipy.pi, both end points excluded. + #. None of the above + +Answer: creates an array of 500 equally spaced elements from + -5*scipy.pi to 5*scipy.pi, both end points included + + +Larger Questions +---------------- + +.. A minimum of 2 questions here (along with answers) + +1. Write a python script to plot a red colour tan plot between -pi to + pi, with x limits from -pi to pi. Label the figure appropriately + and with a legend 'tan(x)' and title 'tangent plot'. Label the axes + x as 'x' and y as 'tan(x)'. Make sure the script can be executed as + a python script. + +2. Write a python script to plot a parabola of the form y^2=4ax with a + = 0.5(a is the directrix), plot the line in green color add the + legend as 'y^2=4ax' and title as 'parabola'. For x from -20 to 20 + with 100 equidistant points. Make sure the script can be executed + as a python script. [`Hint`: Use parametric equations] diff -r 25b4e962b55e -r c7f0069d698a using python modules/script.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/using python modules/script.rst Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,227 @@ +.. 9.3 LO: using python modules (3) +.. --------------------------------- +.. * executing python scripts from command line +.. * import +.. * scipy +.. * pylab +.. * sys +.. * STDLIB modules show off + +==================== +Using Python modules +==================== +{{{ show the welcome slide }}} + +Welcome to the spoken tutorial on using python modules. + +{{{ switch to next slide, outline slide }}} + +In this tutorial, we will see how to run python scripts from command +line, importing modules, importing scipy and pylab modules. + +{{{ switch to next slide on executing python scripts from command line }}} + +Let us create a simple python script to print hello world. Open your +text editor and type the following, + +{{{ open the text editor and type the following }}} +:: + + print "Hello world!" + print + +and save the script as hello.py, + +{{{ save the script as hello.py }}} + +Till now we saw how to run a script using the IPython interpreter +using the +:: + + %run -i hello.py + +option, but that is not the correct way of running a python +script. + +The correct method is to run it using the Python interpreter. Open the +terminal and navigate to the directory where hello.py is, + +{{{ open terminal and navigate to directory where hello.py was saved }}} + +now run the Python script as, +:: + + python hello.py + +It executed the script and we got the output ``Hello World!``. + +{{{ highlight ``python filename`` syntax on slide while narrating }}} + +The syntax is python space filename. + +Now recall the four plot problem where we plotted four plots in a single +figure. Let us run that script from command line. + +If you don't have the script, + +{{{ open the four_plot.py file in text editor }}} + +just pause here and create a python script with the following lines +and save it as four_plot.py. + +Now let us run four_plot.py as a python script. +:: + + python four_plot.py + +Oops! even though it was supposed to work, it didn't. It gave an error +``linspace()`` is not defined, which means that the function +``linspace()`` is not available in the current name-space. + +But if you try to run the same script using ``%run -i four_plot.py`` +in your IPython interpreter started with the option ``-pylab`` it will +work, because the ``-pylab`` option does some work for us by importing +the required modules to our name-space when ipython interpreter +starts. And thus we don't have to explicitly import modules. + +So now let us try to fix the problem and run the script in command +line, + +add the following line as the first line in the script, +{{{ add the line as first line in four_plot.py and save }}} +:: + + from scipy import * + +Now let us run the script again, +:: + + python four_plot.py + +Now it gave another error plot not defined, let us edit the file again +and add the line below the line we just added, +{{{ add the line as second line in four_plot.py and save }}} +:: + + from pylab import * + +And run the script, +:: + + python four_plot.py + +Yes! it worked. So what did we do? + +We actually imported the required modules using the keyword ``import``. +It could have also be done as, + +{{{ highlight the following in slide and say it loud }}} +:: + + from scipy import linspace + +instead of, +:: + + from scipy import * + +So in practice it is always good to use function names instead of +asterisk or star. As if we use asterisk to import from a particular +module then it will replace any existing functions with the same name +in our name-space. + +So let us modify four_plot.py as, +{{{ delete the first two lines and add the following }}} +:: + + from scipy import linspace, pi, sin + from pylab import plot, legend, annotate, title, show + from pylab import xlim, ylim + +{{{ switch to next slide }}} +it could also be done as, + +.. import scipy +.. import pylab +.. x = scipy.linspace(-5*scipy.pi, 5*scipy.pi, 500) +.. pylab.plot(x, x, 'b') +.. pylab.plot(x, -x, 'b') +.. pylab.plot(x, scipy.sin(x), 'g', linewidth=2) +.. pylab.plot(x, x*scipy.sin(x), 'r', linewidth=3) +.. pylab.legend(['x', '-x', 'sin(x)', 'xsin(x)']) +.. pylab.annotate('origin', xy = (0, 0)) +.. pylab.xlim(-5*scipy.pi, 5*scipy.pi) +.. pylab.ylim(-5*scipy.pi, 5*scipy.pi) + + +Notice that we use ``scipy.pi`` instead of just ``pi`` as in the +previous method, and the functions are called as ``pylab.plot()`` and +``pylab.annotate()`` and not as ``plot()`` and ``annotate()``. + +{{{ switch to next slide, problem statement }}} + +Write a script to plot a sine wave from minus two pi to two pi. + +Pause here and try to solve the problem yourself before looking at the +solution. + +It can solved as, + +{{{ open sine.py and show it }}} + +the first line we import the required functions ``linspace()`` and +``sin()`` and constant ``pi`` from the module scipy. the second and +third line we import the functions ``plot()``, ``legend()``, +``show()``, ``title()``, ``xlabel()`` and ``ylabel()``. And the rest +the code to generate the plot. + +We can run it as, +{{{ now switch focus to terminal and run the script }}} +:: + + python sine.py + +{{{ switch to next slide, What is a module? }}} + +So till now we have been learning about importing modules, now what is +a module? + +A module is simply a file containing Python definitions and +statements. Definitions from a module can be imported into other +modules or into the main module. + +{{{ switch to next slide, Python standard library }}} + +Python has a very rich standard library of modules + +Python's standard library is very extensive, offering a wide range of +facilities. Some of the standard modules are, + +for Math: math, random +for Internet access: urllib2, smtplib +for System, Command line arguments: sys +for Operating system interface: os +for regular expressions: re +for compression: gzip, zipfile, tarfile +And there are lot more. + +Find more information at Python Library reference, +``http://docs.python.org/library/`` + +The modules pylab, scipy, Mayavi are not part of the standard python +library. + +{{{ switch to next slide, recap }}} + +This brings us to the end of this tutorial, in this tutorial we +learned running scripts from command line, learned about modules, saw +the python standard library. + +{{{ switch to next slide, thank you slide }}} + +Thank you! + +.. Author: Anoop Jacob Thomas + Reviewer 1: + Reviewer 2: + External reviewer: diff -r 25b4e962b55e -r c7f0069d698a using python modules/sine.py --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/using python modules/sine.py Sat Oct 09 03:56:06 2010 +0530 @@ -0,0 +1,11 @@ +from scipy import linspace, pi, sin +from pylab import plot, legend, show, title +from pylab import xlabel, ylabel + +x = linspace(-2*pi,2*pi,100) +plot(x,sin(x)) +legend(['sin(x)']) +title('Sine plot') +xlabel('x') +ylabel('sin(x)') +show()