--- a/input_output.rst Thu Oct 07 14:25:44 2010 +0530
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-Hello friends and welcome to the tutorial on Input/Output
-
-{{{ Show the slide containing title }}}
-
-{{{ Show the slide containing the outline slide }}}
-
-Input and Output are used in almost every program we use.
-In this tutorial, we shall learn
-
- * Outputting data
- * Taking input from the user
-
-type
-::
-
- a = "This is a string"
- a
- print a
-
-print a prints the value of a which is obvious.
-As you can see, even when you type just a, the value of a is shown.
-But there is a difference.
-
-Typing a shows the value of a while print a prints the string. This difference
-becomes more evident when we use strings with newlines in them.
-type
-::
-
- b = "A line \n New line"
- b
- print b
-
-As you can see, just typing b shows that b contains a newline character.
-While typing print b prints the string and hence the newline.
-
-Moreover when we type just a, the value a is shown only in interactive mode and
-does not have any effect on the program while running it as a script.
-
-We shall look at different ways of outputting the data.
-
-print statement also accepts the syntax of C's printf statement.
-Various arguments can be passed to print using modifiers.
-type
-::
-
- x = 1.5
- y = 2
- z = "zed"
- print "x is %2.1f y is %d z is %s"%(x,y)
-
-As you can see, the values of x and y are substituted in place of %2.1f and %d
-
-{{{ Pause here and try out the following exercises }}}
-
-%% 1 %% What happens when you do print "x is %d y is %f"%(x)
-
-{{{ continue from paused state }}}
-
-We see that the int value of x and float value of y are printed corresponding
-to the modifiers used in the print statement.
-
-We can also see that print statement prints a new line character at the end of
-line, everytime it is called. This can be suppressed by using a "," at the end
-print statement.
-
-Let us see this by typing out following code on an editor as print_example.py
-
-{{{ open an editor }}}
-type
-::
-
- print "Hello"
- print "World"
-
- print "Hello",
- print "World"
-
-Now we run the script using %run /home/fossee/print_example.py
-
-As we can see, the print statement when used with comma in the end, prints a
-space instead of a new line.
-
-Now we shall look at taking input from the user.
-We will use the ~~raw_input~~ for this.
-type
-::
-
- ip = raw_input()
-
-The cursor is blinking indicating that it is waiting for input
-type
-::
-
- an input
-
-and hit enter.
-Now let us see what is the value of ip by typing.
-::
-
- ip
-
-We can see that it contains the string "an input"
-
-{{{ Pause here and try out the following exercises }}}
-
-%% 2 %% enter the number 5.6 as input and store it in a variable called c.
-
-{{{ continue from paused state }}}
-
-We have to use the raw_input command with variable c.
-type
-::
-
- c = raw_input()
- 5.6
- c
-
-Now let us see the type of c.
-
-::
-
- type(c)
-
-We see that c is a string. This implies that anything you enter as input, will
-be taken as a string no matter what you enter.
-
-{{{ Pause here and try out the following exercises }}}
-
-%% 3 %% What happens when you do not enter anything and hit enter
-
-{{{ continue from paused state }}}
-
-::
-
- d = raw_input()
- <RET>
- d
-
-We see that when nothing is entered, an empty string is considered as input.
-
-raw_input also can display a prompt to assist the user.
-::
-
- name = raw_input("Please enter your name: ")
-
-prints the string given as argument and then waits for the user input.
-
-{{{ Pause here and try out the following exercises }}}
-
-%% 4 %% How do you display a prompt and let the user enter input in a new line
-
-{{{ continue from paused state }}}
-
-The trick is to include a newline character at the end of the prompt string.
-::
-
- ip = raw_input("Please enter a number in the next line\n> ")
-
-prints the newline character and hence the user enters input in the new line
-
-{{{ Show summary slide }}}
-
-This brings us to the end of the tutorial.
-we have learnt
-
- * How to print some value
- * How to print using modifiers
- * How to take input from user
- * How to display a prompt to the user before taking the input
-
-{{{ Show the "sponsored by FOSSEE" slide }}}
-
-#[Nishanth]: Will add this line after all of us fix on one.
-This tutorial was created as a part of FOSSEE project, NME ICT, MHRD India
-
-Hope you have enjoyed and found it useful.
-Thankyou
-
-.. Author : Nishanth
- Internal Reviewer 1 :
- Internal Reviewer 2 :
- External Reviewer :
-
-Questions
-=========
-
- 1. ``a = 2.5``. What is the output of ``print "a is %d"%(a)``
-
- a. a is 2.5
- #. a is 2.0
- #. 2.0
- #. a is 2
-
- Answer: a is 2
-
- 2. What does ``print "This is", "a line ", "with spaces"`` print?
-
- a. This is a line with spaces
- #. This is a line with spaces
- #. This is a line with spaces
- #. This is a line with spaces
-
- Answer: This is a line with spaces
-
- 3. What does ``print "%2.5f"%(1.2)`` print?
-
- a. 1.2
- #. 1.20
- #. 1.20000
- #. 00001.2
-
- Answer: 1.20000
-
- 4. What is the output of the following code::
-
- for i in range(1,10,2):
- print i,
-
- Answer::
-
- 1 3 5 7 9
-
- 5. ``a = 2`` and ``b = 4.5``. What does ``print "a is %d and b is %2.1f"%(b, a)``
- print?
-
- a. a is 2 and b is 4.5
- #. a is 4 and b is 2
- #. a is 4 and b is 2.0
- #. a is 4.5 and b is 2
-
- Answer: a is 4 and b is 2.0
-
- 6. What is the prompt displayed by ``raw_input("Say something\nType here:")``
-
- Answer::
-
- Say something
- Type here:
-
- 6. What is the prompt displayed by ``raw_input("value of a is %d\nInput b
- value:"a)`` and ``a = 2.5``
-
- Answer::
-
- value of a is 2
- Input ba value:
-
- 7. ``a = raw_input()`` and user enters ``2.5``. What is the type of a?
-
- a. str
- #. int
- #. float
- #. char
-
- Answer: str
-
- 8. ``a = int(raw_input())`` and user enters ``4.5``. What happens?
-
- a. a = 4.5
- #. a = 4
- #. a = 4.0
- #. Error
-
- Answer: Error
-
- 9. ``a = raw_input()`` and user enters ``"this is a string"``. What does
- ``print a`` produce?
-
- a. 'this is a string'
- b. 'this is a string"
- c. "this is a string"
- #. this is a string
-
- Answer: "this is a string"
-
-Problems
-========
-
- 1. Answer to universe and everything. Keep taking input from user and print it
- back until the input is 42.
-
- Answer::
-
- ip = raw_input()
- while ip != "42":
- print ip
-
- 2.