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-*Script
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-
-*Hello and welcome to this tutorial on Basic Python using Python.
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-This tutorial formally introduces Python as a language . Through this tutorial we will be able to understand Basic Data types like number , Boolean and strings .Some basic operators , simple input/output and basic conditional flow .
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-In numbers Python supports three kinds of data types ,
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-floats,integers and complex numbers
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-An integer can be defined as follows :
-a=13
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-This make a an integer variable with value 13 .
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-You can also type 9 around 20 times
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-a=99999999999999999999999 . as you can see Python does not have a limit on how long an integer has to be . Isn't that great .
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-Now will try a float.
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-let's type
-p=3.141592 if you type out p now you will notice that it is not absolutely equal to p you typed in . The reason for that is how a computer saves decimal values .
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-Apart from integer and float, Python has an in-built support for complex numbers. Now we try to assign a complex value to a variable .
-Type:
-c = 3+4j
-As you can see ,the notation for complex numbers is similar to the one used in electric engineering.
-We will now try some operations on complex numbers . First we will try to get the absolute value of the complex number . For this we will use the abs built in function . For this do :
-abs in parenthesis c .
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-Do get the imaginary part of c you can do :
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-c.imag
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-and similarly for real part do :
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-c.real
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-Python also has Boolean as a built-in type .
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-Try it out just type ..
- t=True , note that T in true is capitalized .
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-You can apply different Boolean operations on t now for example :
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-f=not t , this saves the value of not t that is False in f.
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-We can apply other operators like or and and ,
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-f or t gives us the value True while
-f and t gives us the value false.
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-You can use parenthesis for precedence ,
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-Lets write some piece of code to check this out .
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-a=False
-b=True
-c=True
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-To check how precedence changes with parenthesis . We will try two expressions and their evaluation.
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-do
-(a and b) or c
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-This expression gives the value True
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-where as the expression a and (b or c) gives the value False .
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-Now we will have a look at strings
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-type
-w="hello"
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-w is now a string variable with the value "hello"
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-printing out w[0] + w[2] + w[-1] gives hlo if you notice the expression for accessing characters of a string is similar to lists .
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-Also functions like len work with strings just like the way they did with lists
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-Now lets try changing a character in the string in the same way we change lists .
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-type :
-w[0]='H'
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-oops this gives us a Type Error . Why? Because string are immutable . You can change a string simply by assigning a new element to it . This and some other features specific to string processing make string a different kind of data structure than lists .
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-Now lets see some of the ways in which you can modify strings and other methods related to strings .
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-Type :
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-a = 'Hello world'
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-To check if a particular string starts with a particular substring you can check that with startswith method
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-a.startswith('Hell')
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-Depending on whether the string starts with that substring the function returns true or false
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-same is the case a.endwith('ld')
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-a.upper()
- returns another string that is all the letters of given string capitalized
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-similarly a.lower returns all small letters .
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-Earlier we showed you how to see documentations of functions . You can see the documentation of the lower function by doing a.lower?
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-You can use a.join to joing a list of strings to one string using a given string as connector .
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-for example
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-type :
-', '.join(['a','b','c'])
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-In this case strings are joined over , and space
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-Python supports formatting values into strings. Although this can include very complicated expressions, the most basic usage is to insert values into a string with the %s placeholder. %d can be used for formatting things like integers and %f for floats
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-Their are many other string formatting options you can look at http://docs.python.org/library/stdtypes.html for more information on other options available for string formatting.
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-Operators ---- Probably can be a different chapter .
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-We will start the discussion on operators first with arithmetic operators .
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-% can be used for remainder for example
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-864675 % 10 gives remainder 5
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-you can use 2 *'s for power operation
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-for example 4 ** 3 gives the result 64
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-One thing one should notice is the type of result depends on the types of input for example :
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-17 / 2 both the values being integer gives the integer result 2
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-however the result when one or two of the operators are float is float for example:
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-17/2.0
-8.5
-17.0/2.0
-8.5