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diff --git a/getting_started_with_functions/script.rst b/getting_started_with_functions/script.rst index 26e5b79..4288224 100644 --- a/getting_started_with_functions/script.rst +++ b/getting_started_with_functions/script.rst @@ -18,6 +18,8 @@ .. 1. should have ``ipython`` installed. .. #. getting started with ``ipython``. +.. #. Conditionals +.. #. Loops .. Author : Anoop Jacob Thomas <anoop@fossee.in> @@ -31,116 +33,217 @@ Getting started with functions ============================== -{{{ show welcome slide }}} +.. L1 -Hello and welcome to the tutorial getting started with functions. +{{{ Show the first slide containing title, name of the production +team along with the logo of MHRD }}} -{{{ switch to next slide, outline slide }}} +.. R1 -In this tutorial we will learn about functions in python, how to -define functions, arguments to functions, docstrings, and function -return value. +Hello friends and welcome to the tutorial 'Getting started with functions'. + +.. L2 + +{{{ switch to slide containing objectives }}} + +.. R2 + +At the end of this tutorial, you will be able to, + + 1. Define a function. + #. Define functions with arguments. + #. Learn about docstrings. + #. Learn about function return value. + #. Read code. + +.. L3 + +{{{ Switch to the pre-requisite slide }}} + +.. R3 + +Before beginning this tutorial,we would suggest you to complete the +tutorial on "Conditionals" and "Loops". + +.. L4 {{{ switch to next slide, Function }}} +.. R4 + While writing code, we always want to reduce the number of lines of -code and functions is a way of reusing the code. Thus the same lines +code, and functions is a way of reusing the code. Thus the same lines of code can be used as many times as needed. A function is a portion of code within a larger program that performs a specific task and is relatively independent of the remaining code. Now let us get more familiar with functions, +.. L5 + {{{ switch to next slide, f(x) a mathematical function }}} +.. R5 + Consider a mathematical function f(x) = x square. Here x is a variable and with different values of x the value of function will change. When -x is one f(1) will return the value 1 and f(2) will return us the +x is one, f(1) will return the value 1 and f(2) will return us the value 4. Let us now see how to define the function f(x) in python. -{{{ switch to next slide, define f(x) in Python }}} +.. R6 + +Start your ipython interpreter by typing, -In your Ipython interpreter type the following, +.. L6 + +{{{ Open the terminal }}} +:: + + ipython + +.. R7 + +Let us define our function f(x) + +.. L7 :: def f(x): return x*x +.. R8 + Well that defined the function, so before learning what we did let us see if it returns the expected values, try, + +.. L8 :: f(1) f(2) +.. R9 + Yes, it returned 1 and 4 respectively. And now let us see what we did. We wrote two lines: The first line ``def f(x)`` is used to define the -name and the parameters to the function and the second line is used to +name and the parameters to the function, and the second line is used to fix what the function is supposed to return. ``def`` is a keyword and ``f`` is the name of the function and ``x`` the parameter of the function. -{{{ switch to next slide, problem statement 1 }}} +Pause the video here, try out the following exercise and resume the video. + +.. L9 + +.. L10 + +{{{ Show slide with exercise 1 }}} + +.. R10 + + Write a python function named ``cube`` which computes the cube of + a given number n. -%% 1 %% Write a python function named cube which computes the cube of - a given number n. +.. R11 -Pause here and try to solve the problem yourself. +Switch to your terminal for solution.The problem can be solved as, -{{{ switch to next slide, solution }}} +.. L11 -The problem can be solved as, +{{{continue from paused state}}} +{{{ Switch to the terminal }}} :: def cube(n): return n**3 -And now let us see how to write functions without arguments. +.. R12 + +Let us check whether our function returns the cube of a number or not + +.. L12 +:: -{{{ switch to next slide, greet function }}} + cube(2) + +.. R13 + +It returned 8,which means we have defined our function,the right way. +And now let us see how to write functions without arguments. let us define a new function called ``greet`` which will print ``Hello World``. + +.. L13 :: def greet(): print "Hello World!" -now try calling the function, +.. R14 + +now we call the function as, + +.. L14 :: greet() +.. R15 + Well that is a function which takes no arguments. Also note that it is not mandatory for a function to return values. The function ``greet`` neither takes any argument nor returns any value. Now let us see how to write functions with more than one argument. -{{{ switch to next slide, exercise 2 }}} +Pause the video here, try out the following exercise and resume the video. + +.. L15 + +.. L16 + +{{{ Show slide with exercise 2 }}} -%% 2 %% Write a python function named ``avg`` which computes the - average of ``a`` and ``b``. +.. R16 -Pause here and try to solve the problem yourself. + Write a python function named ``avg`` which computes the + average of ``a`` and ``b``. -{{{ switch to next slide, solution 2 }}} +.. R17 -The problem can be solved as, +Switch to your terminal for solution. + +.. L17 + +{{{continue from paused state}}} +{{{ Switch to the terminal }}} :: def avg(a,b): return (a + b)/2 +.. R18 + +Let us test our function + +.. L18 +:: + + avg(20, 30) + +.. R19 + +We get the correct average, 25. Thus if we want a function to accept more arguments, we just list them separated with a comma between the parenthesis after the function's name in the ``def`` line. -{{{ switch to next slide, docstring }}} - It is always a good practice to document the code that we write, and -for a function we define we should write an abstract of what the +for a function we define, we should write an abstract of what the function does, and that is called a docstring. Let us modify the function ``avg`` and add docstring to it. Do the following, + +.. L19 :: def avg(a,b): @@ -148,35 +251,63 @@ function ``avg`` and add docstring to it. Do the following, returns the average of a and b""" return (a+b)/2 +.. L20 + +{{{ switch to next slide, docstring }}} + +.. R20 + Note that docstrings are entered in the immediate line after the function definition and put as a triple quoted string. And here as far as the code functionality is concerned, we didn't do anything. We just added an abstract of what the function does. +.. R21 + Now try this in the ipython interpreter. + +.. L21 + +{{{ Switch to the terminal }}} :: avg? +.. R22 + It displays the docstring as we gave it. Thus docstring is a good way of documenting the function we write. -Try to do this, + Now type, + +.. L22 :: f? +.. R23 + It doesn't have a docstring associated with it. Also we cannot infer anything from the function name, and thus we are forced to read the code to understand about the function. -{{{ switch to next slide, exercise 3 }}} +Pause the video here, try out the following exercise and resume the video. + +.. L23 + +.. L24 + +{{{ Show slide with exercise 3 }}} -%% 3 %% Add docstring to the function f. +.. R24 -Pause here and try to do it yourself. + Add docstring to the function f. -{{{ switch to next slide, solution }}} +.. L25 + +{{{ Show slide with solution 3 }}} + +.. R25 We need to define the function again to add docstring to the function ``f`` and we do it as, @@ -187,17 +318,28 @@ We need to define the function again to add docstring to the function returns the square of the number x.""" return x*x -{{{ switch to next slide, exercise 4 }}} +Let us solve one more exercise +Pause the video here, try out the following exercise and resume the video. + +.. L27 -%% 4 %% Write a python function named ``circle`` which returns the - area and perimeter of a circle given radius ``r``. +{{{ Show slide with exercise 4 }}} -Pause here and try to solve the problem yourself. +.. R27 -{{{ switch to next slide, solution 4 }}} + Write a python function named ``circle`` which returns the + area and perimeter of a circle given radius ``r``. + +.. R28 + +Switch to the terminal for solution. The problem requires us to return two values instead of one which we were doing till now. We can solve the problem as, + +.. L28 + +{{{ Switch to the terminal }}} :: def circle(r): @@ -207,21 +349,31 @@ were doing till now. We can solve the problem as, perimeter = 2 * pi * r return area, perimeter +.. R29 + A python function can return any number of values. There is no restriction for it. Let us call the function ``circle`` as, + +.. L29 :: a, p = circle(6) print a print p +.. R30 + Now we have done enough coding, let us do some code reading exercise, +.. L30 + {{{ switch to next slide, what }}} -What does the function ``what`` do? +.. R31 + +Pause here and try to figure out what the function ``what`` does. .. def what( n ): .. if n < 0: n = -n @@ -231,13 +383,18 @@ What does the function ``what`` do? .. n /= 10 .. return True -Pause here and try to figure out what the function ``what`` does. +{{{continue from paused state}}} +It will return true if ``n % 2`` is not equal to 1 and will return false, otherwise. + +.. L31 + +.. L32 {{{ switch to next slide, even_digits }}} .. def even_digits( n ): -.. """returns True if all the digits in the number n are even, -.. returns False if all the digits in the number n are not even""" +.. """returns True if all the digits in the number n are even, +.. returns False if all the digits in the number n are not even""" .. if n < 0: n = -n .. while n > 0: .. if n % 2 == 1: @@ -245,14 +402,20 @@ Pause here and try to figure out what the function ``what`` does. .. n /= 10 .. return True -The function returns ``True`` if all the digits of the number ``n`` +.. R32 + +The function here returns ``True`` if all the digits of the number ``n`` are even, otherwise it returns ``False``. Now one more code reading exercise, +.. L33 + {{{ switch to next slide, what }}} -What does the function ``what`` do? +.. R33 + +Pause here and try to figure out what the function ``what`` does. .. def what( n ): .. i = 1 @@ -260,7 +423,11 @@ What does the function ``what`` do? .. i += 1 .. return i * i == n, i -Pause here and try to figure out what the function ``what`` does. +{{{continue from paused state}}} +The function returns two values. One it returns the result of the while statement +whether true of false, and second it prints the value that `ii`` currently holds. + +.. L34 {{{ switch to next slide, is_perfect_square }}} @@ -273,21 +440,81 @@ Pause here and try to figure out what the function ``what`` does. .. i += 1 .. return i * i == n, i +.. R34 -The function returns ``True`` and the square root of ``n`` if n is a +Here, the function returns ``True`` and the square root of ``n`` if n is a perfect square, otherwise it returns ``False`` and the square root of the next perfect square. -This brings us to the end of this tutorial, in this tutorial we covered +.. L35 + +{{{ switch to summary slide }}} + +.. R35 + +This brings us to the end of this tutorial. In this tutorial, +we have learnt to, + + 1. Define functions in Python by using the keyword ``def``. + #. Call the function by specifying the function name. + #. Assign a docstring to a function by putting it as a triple quoted string. + #. Pass parameters to a function. + #. Return values from a function. + +.. L26 + +{{{Show self assessment questions slide}}} + +.. R36 + +Here are some self assessment questions for you to solve -{{{ switch to next slide, summary }}} +1. What will the function do? +:: + + def what(x) + return x*x + + - Returns the square of x + - Returns x + - Function doesn't have docstring + - Error + +2. How many arguments can be passed to a python function? + + - None + - One + - Two + - Any + +3. Write a function which calculates the area of a rectangle. + +.. L37 + +{{{solution of self assessment questions on slide}}} + +.. R37 + +And the answers, + +1. The function will result into an error due to the use of wrong + syntax in defining the function.The function line should always + end with a colon + +2. Any number of arguments can be passed to a python function. + +3. As we know, area of a rectangle is product of it's length and breadth. + Hence, we define our function as, +:: -- Functions in Python -- Passing parameters to a function -- Returning values from a function + def area(l,b): + return l * b -We also did few code reading exercises. +.. L38 + +{{{ switch to Thank you slide }}} -{{{ switch to next slide, Thank you }}} +.. R38 +Hope you have enjoyed this tutorial and found it useful. Thank you! |