Python-3.4.3/C4/Getting-Started-with-Functions/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:01 | Welcome to the spoken tutorial on Getting started with functions. |
| 00:06 | In this tutorial, we will learn to,
Define a function Define functions with arguments and use docstrings. |
| 00:17 | To record this tutorial, I am using
Ubuntu Linux 16.04 operating system Python 3.4.3 and IPython 5.1.0 |
| 00:32 | To practise this tutorial, you should know how to use tuples.
If not, see the relevant Python tutorials on this website. |
| 00:44 | First we will learn about functions. |
| 00:48 | A function is a portion of code within a larger program that performs a specific task. |
| 00:55 | Functions are useful in reusing the code and eliminate code redundancy. |
| 01:01 | Functions are also used to organise our code into manageable blocks. |
| 01:07 | Here is the syntax for defining the functions. |
| 01:11 | def is the keyword which defines the function name. |
| 01:15 | colon is used to mark the end of the function name. |
| 01:19 | docstring is the documentation string to describe what the function does.
It is an optional, but recommended. |
| 01:29 | Statement makes the function body and it must have 4 indentation level. |
| 01:36 | return statement is to return a value from the function and it is also indented by 4 spaces. |
| 01:44 | Now we will understand the functions with an example. |
| 01:49 | Consider a mathematical function f of x is equal to x squared. |
| 01:55 | Here x is a variable. f of x changes when x changes. |
| 02:02 | Let us define our function f of x. |
| 02:06 | The first line def f of x is used to define the function name and its parameters. |
| 02:13 | The second line uses the function parameters to return the required value. |
| 02:19 | Let us start ipython.
Open the terminal. |
| 02:24 | Type ipython3 and press Enter. |
| 02:29 | From here onwards, remember to press the Enter key after typing every command on the terminal. |
| 02:36 | Type,
def f inside brackets x colon return x asterisk x and press the Enter key two times. |
| 02:47 | Let us call the f of x with different arguments. |
| 02:51 | Type,
f inside brackets 2 f inside brackets 2.5 It returned 4 and 6.25 respectively. |
| 03:05 | Now let us see how to write functions without arguments. |
| 03:10 | Type the code as shown.
It defines a new function named greet which will print "No function arguments" |
| 03:21 | Now we will call the function as,greet open and close parentheses |
| 03:28 | Note that it is not mandatory for a function to return values. |
| 03:33 | The function greet neither takes any arguments nor returns any value. |
| 03:40 | Next we will learn how to comment in a code. |
| 03:44 | Documenting/commenting code is a good practice. |
| 03:48 | Docstrings are triple quoted comments entered just after the function definition.
It implies what the function does. |
| 03:57 | Let us write a function which returns average of two numbers. |
| 04:02 | Type the code as shown. and press the Enter key two times.
Comments within triple quotes give a clear explanation about the code. |
| 04:14 | Type, avg question mark
Here we can see the docstring of the function avg. |
| 04:23 | Now let us pass 3 and 5 as values to the arguments a and b to the function avg. |
| 04:31 | Type, avg inside brackets 3 comma 5 We get 4.0 as output. |
| 04:41 | Pause the video.Try this exercise and then resume the video. |
| 04:47 | Write a function circle which returns the area and perimeter of a circle with given radius r. |
| 04:54 | Switch back to the terminal for the solution. |
| 04:58 | Type the code as shown. Press the Enter key two times. |
| 05:05 | The circle function requires us to return two values. |
| 05:10 | A python function can return any number of values in the form of a tuple. |
| 05:16 | Let us call the function circle as, a comma p is equal to circle inside brackets 6 |
| 05:25 | Now Type, print inside brackets a comma p |
| 05:31 | We can see the output as area and perimeter of a circle of radius 6. |
| 05:38 | This brings us to the end of this tutorial. Let us summarize. |
| 05:44 | In this tutorial, we have learnt to,
Define functions in Python Call a function by specifying the function name |
| 05:54 | Write docstrings to a function by putting it as a triple quoted string
Pass parameters to a function Return values from a function. |
| 06:06 | Here are some self assessment questions for you to solve
1. How many arguments can be passed to a Python function? |
| 06:15 | 2.Write a function to find the area of a rectangle. |
| 06:20 | And the answers,
1. Any number of arguments can be passed to a Python function. |
| 06:28 | 2. We can write a function to find the area of a rectangle as:def rectangle underscore area inside brackets l comma b colon
return l asterisk b |
| 06:42 | Please post your timed queries in this forum. |
| 06:46 | Please post your general queries on Python in this forum. |
| 06:51 | FOSSEE team coordinates the TBC project. |
| 06:55 | Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India. For more details, visit this website. |
| 07:04 | This is Priya from IIT Bombay signing off. Thanks for watching. |
