Python/C4/Advanced-features-of-functions/English-timed

Visual Cue	Narration
0:01	Hello friends and Welcome to the tutorial on 'advanced features of functions'.
0:06	At the end of this tutorial, you will be able to, Assign default values to arguments, when defining functions. Define and call functions with keyword arguments. Learn some of the built-in functions available in Python standard library and the scientific computing libraries.
0:23	Before beginning this tutorial,we would suggest you to complete the tutorial on "Getting started with functions".
0:32	Let us Start the ipython interpreter in command
0:36	ipython hypen pylab in command
0:43	Let's use the round function as an example to understand what a default value of an argument means.
0:49	Let's type the following expressions in the terminal.
0:52	Type round within bracket 2.484 and hit enter. Then type round 2.484 comma 2
1:10	Both the first expression and the second are calls to the round function, but the first calls it with only one argument and the second calls it with two arguments.
1:22	By observing the output, we can guess that the first one is equivalent to call with the second argument being 0. 0 .
1:30	s.strip() # strips on spaces.
1:35	s.strip within single quote at the rate # strips the string of 'at the rate' symbols.
1:47	Thus it can be said that here, blank space is the default argument.
1:52	plot within bracket x comma y # plots with x versus y using default line style. plot within bracket x comma y comma in single quote o # plots x versus y with circle markers.
2:14	Hence, here when third argument is not provided, it shows default line style.
2:20	linspace within bracket 0 comma 2 star pi comma 100 # returns 100 points between 0 and 2pi linspace within bracket 0 comma 2 star pi # returns 50 points between 0 and 2pi
2:37	Hence, the default for the third argument is 50.
2:42	Let's now define a simple function that uses default arguments.
2:46	We define a simple function that prints a welcome message to a person, given a greeting and his/her name.
2:54	So type in the terminal def welcome within bracket greet comma name= within double quotes World colon (hit enter) print greet comma name (hit enter)
3:18	Let us first call the function with two arguments, one for greet and other for name .
3:25	So type welcome and in bracket within double quotes Hi comma within double quotes Guido
3:35	We get the expected welcome message, "Hi Guido".
3:41	Now let us call the function with just one argument "Hello".
3:45	So type welcome within bracket within double quotes Hello
3:53	"Hello" is treated as the greet and we get "Hello World" as the output.
3:59	"World" is the default value for the argument name .
4:02	Pause the video here, try out the following exercise and resume the video.
4:07	Redefine the function welcome , by interchanging it's arguments.
4:11	Place the name argument with it's default value of "World" before the greet argument.
4:17	Switch to the terminal for solution
4:20	def welcome within bracket name= within double quotes World comma greet colon (hit enter) print greet comma name (hit enter)
4:36	We get an error that reads SyntaxError: non-default argument follows default argument .Then ipython control line one.
4:47	When defining a function all the argument with default values should come at the end.
4:52	Pause the video here, try out the following exercise and resume the video.
4:58	See the definition of linspace using question mark and make a note of all the arguments with default values are towards the end.
5:09	Switch to the terminal for solution
5:12	linspace question mark hit enter
5:17	As we go on hitting the enter key, we the the number of arguments this command has.
5:26	Please read the content on your terminal.
5:30	Again,Pause the video here,try out the following exercise and resume the video.
5:35	Redefine the function welcome with a default value of
5:41	"Hello" to the greet argument.
5:44	Then, call the function without any arguments.
5:48	Switch to the terminal for solution
5:51	Type def welcome within bracket greet= within double quotes Hello comma name= in double quotes World colon print greet comma name (After hitting enter type) welcome()
6:17	As we can see, we get the output as Hello World .
6:20	Let us now learn what keyword arguments or named arguments are.
6:26	We shall refer to them as keyword arguments, henceforth.
6:31	When you are calling functions in Python, you don't need to remember the order in which to pass the arguments.
6:38	Instead, you need the name of the argument to pass it a value.
6:44	This slide shows a few function calls that use keyword arguments.
6:52	loc , linewidth , xy and labels< are being called with keyword arguments.
7:00	Let us try and understand this better using the welcome function that we have been using all along.
7:07	Let us call it in different ways and observe the output to see how keyword arguments work.
7:14	So type in terminal type welcome() welcome within bracket within double quotes Hello comma double quotes James welcome within bracket within double quotes Hi comma name= within double quotes Guido
7:37	When no keyword is specified, the arguments are allotted based on their position.
7:42	So, "Hi" is the value of the argument greet and name is passed the value "Guido".
7:48	If we type on the terminal welcome within bracket name= within double quotes Guido comma greet= within double quotes Hey exclamation
8:02	When keyword arguments are used, the arguments can be called in any order.
8:07	And if we call our function as,welcome within bracket name="Guido" comma "Hey"
8:17	This call returns an error that reads, non-keyword arg after keyword arg . Python expects all the keyword to be present towards the end.
8:30	That brings us to the end of what we wanted to learn about keyword arguments.
8:37	Before defining a function of your own, make sure that you check the standard library, for a similar function.
8:43	Python is popularly called a "Batteries included" language, for the huge library that comes along with it.
8:55	Math functions - abs, sin, .... Plot functions - plot, bar, pie ... Boolean functions - and, or, not ...
9:11	Apart from the standard library there are other libraries like pylab , scipy , etc which have a huge collection of functions for scientific purposes.
9:22	pylab has
9:23	plot, bar, contour, boxplot, errorbar, log, polar, quiver, semilog
9:32	scipy (modules)has
9:35	fftpack, stats, linalg, ndimage, signal, optimize, integrate
9:46	This brings us to the end of this tutorial.
9:48	In this tutorial, we have learnt to, 1. Define functions with default arguments.
9:53	2. Call functions using keyword arguments.
9:55	3. Use the range of functions available in the Python standard library and the Scientific Computing related packages.
10:04	Here are some self assessment questions for you to solve
10:08	1. All arguments of a function cannot have default values. - True or False?
10:14	2. The following is a valid function definition.
10:17	True or False?
10:21	def separator within bracket count=40 comma char comma show=False colon if show colon print char star count return char star count
10:36	3. When calling a function, the arguments should always be in the order in which they are defined.
10:45	the arguments can be in any order.
10:47	only keyword arguments can be in any order, but should be called at the beginning.
10:56	only keyword arguments can be in any order, and should be called at the end.
11:10	So now we can look at the answers,
11:13	1.False.
11:15	All arguments of a Python function can have default values.
11:21	2. False.
11:23	All parameters with default arguments should be defined at the end.
11:27	3. When calling a function,only keyword arguments can be in any order, but should be called at the end.
11:35	Hope you have enjoyed this tutorial and found it useful.
11:39	Thank you!

Contributors and Content Editors

Gaurav, Minal, PoojaMoolya, Sneha