Python/C2/Getting-started-with-ipython/English-timed

Time	Narration
00:00	Hello friends and welcome to the tutorial on Getting started with ipython.
00:07	At the end of this tutorial, you will be able to: invoke the ipython interpreter . quit the ipython interpreter. navigate the ipython session history. use tab-completion for writing ipython functions. look-up documentation of functions. interrupt incomplete or incorrect commands.
00:27	iPython is an enhanced Python interpreter that provides features like tab-completion, easier access to help and many other functionalities.
00:37	Let us first see how to start the ipython interpreter.
00:41	First, open the terminal. Type: "ipython" in the terminal and hit Enter.
00:51	After getting some information about the version of Python installed and some help commands, we get a prompt with In[1]:.
00:59	But, if you get an error saying 'ipython is not installed' then refer to the tutorial on how to install the packages.
01:09	Now, let's see how we can quit the 'ipython interpreter'. Press Ctrl, D.
01:17	A prompt will appear to confirm whether you really want to exit; type 'y' to say 'yes' and quit 'ipython' and 'n' to say 'no' if you don't want to quit the ipython.
01:28	Press 'y'.
01:32	Now, since we have quit the interpreter, let us start it again by typing "ipython".
01:42	And now let's see, how to use the interpreter.
01:46	Start with the simplest thing, addition.
01:48	type: 1+2at the prompt.
01:55	iPython promptly gives back the output as 3.
01:59	Notice that the output is displayed with an Out[1] indication.
02:05	Now, let us try few more operations such as- 5 minus 3, 7 minus 4, 6 into 5.
02:23	Now, let's see how the ipython remembers the history of commands.
02:29	For example,print 1+2.
02:33	Instead of typing the whole thing, use the up-arrow key to go back to the command 1+2 which we did before. Now use the left-arrow key to navigate to the beginning of the line and type the word "print" and press space.
02:55	We have changed the line to print 1+2, now press Enter.
03:02	The interpreter prints the result as 3.
03:06	Please note that the indication Out square brackets is not shown here.
03:11	Now, let us do print 10 into 2.
03:16	We use the up-arrow key to navigate to the previous command 1+2.
03:22	Now, change 1 plus 2 to 10 into 2 and press Enter.
03:34	Till now, we saw how to invoke the 'ipython interpreter', quit the ipython and navigate through previous commands in ipython.
03:42	Now, let's see, what is tab-completion?.
03:47	Let's take an example. Suppose, we want to use the function round.
03:52	For this, we just type ro at the prompt and press the tab key.
04:00	As you can see on the terminal, IPython completes the command ro into round. This feature of ipython is called the tab-completion.
04:08	Let's see some more possibilities of tab completion just type r and then press the tab.
04:19	As you can see that IPython does not complete the command. This is because, there are many possibilities of r therefore it just lists out all the possible completions of 'r'.
04:31	Now, let's try out an exercise.
04:33	Pause the video, solve the problem and resume the video.
04:39	1. Find out the commands starting with "ab"?
04:44	2. List out the commands starting with "a"?
04:54	ab tab completes toabs and a tab gives us a list of all the commands starting with 'a'.
05:07	Now, let's see what the functions 'abs' is used for.
05:12	We will use the help features of ipython to find out this.
05:15	To see the documentation of a function, type the function name followed by a question mark and hit Enter.
05:24	ipython interpreter will show the documentation for the function.
05:27	Let us see the documentation of the function 'abs', type: "abs?" and press Enter.
05:38	As the documentation says, abs accepts a number as an input and returns it's absolute value.
05:46	Let's see few examples.
05:49	Type: abs(-19) and abs(19) on the interpreter.
06:04	We get 19 as expected, in both the cases.
06:08	Now let's try it for decimal numbers; let's try abs(-10.5), we got 10.5 as the result.
06:24	Pause the video here, try out the following exercise and resume the video.
06:31	Look-up the documentation of round and see how to use it.
06:39	And you can look up the documentation of the function round by typing round question mark in the 'ipython interpreter'.
06:47	If you notice, there are extra square brackets around ndigits.
06:53	This means that ndigits is optional and 0 is the default value.
06:58	Optional parameters are shown in square brackets in Python documentation.
07:03	A function round, rounds a number to a given precision.
07:09	Pause the video here, try out the following exercise and resume the video.
07:16	Let us now try few more examples with the function round.
07:21	Check the output of round(2.48) round(2.48, 1) round(2.48, 2) round(2.484) round(2.484, 1) round(2.484, 2).
07:43	Now, we got 2.0, 2.5 and 2.48 which are what we expect.
07:54	Let's now see how to correct typing errors which we often make while typing at the terminal.
08:01	As already shown, if we haven't hit the Enter key already, we could navigate using the arrow keys and make deletions using delete or backspace key and correct the errors.
08:12	Let us make a typing error deliberately, type: round(2.484 and hit Enter, without closing the parenthesis.
08:25	We get a prompt with dots .
08:28	This prompt is the continuation prompt of ipython.
08:32	It appears when the previous line is incomplete.
08:36	Now complete the command of the same example with close parenthesis and press Enter.
08:49	We got the expected output that is 2.0
08:51	In other instances, if we commit a typing error with a longer and more complex expression and end up with the continuation prompt, we can type Ctrl-C to interrupt the command and get back to the ipython input prompt.
09:15	Pause the video here, try out the following exercise and resume the video.
09:22	1. Type round(2.484, and press Enter and then cancel the command using Ctrl-C.
09:45	2. Type the command- round(2.484, 2)
10:09	Now, let us revise quickly what we learn't today. In this tutorial, we learn't to:
10:15	1. Invoke the 'ipython interpreter' by typing 'ipython'.
10:20	2. To quit the 'ipython interpreter' by using Ctrl-d.
10:22	3. To navigate in the history of ipython by using the arrow keys.
10:28	4. What is tab-completion.
10:30	5. To see the documentation of functions using question mark.
10:34	6. To Interrupt using Ctrl-c when we make an error.
10:39	Here are some self assessment questions for you to solve-
10:44	ipython is a programming language similar to Python.
10:50	True or False?
10:53	Second one. Which key combination quits ipython ? Ctrl + C Ctrl + D Alt + C Alt + D.
11:03	And The last one. Which character is used at the end of a command, in Ipython to display the documentation. under score (_), question mark (?), exclamation mark (!), ampersand (&).
11:16	And the answers are-
11:18	Ipython is not a programming language, it is just an interpreter.
11:23	Second one is We use Ctrl D to quit 'ipython interpreter'.
11:27	The final one is- We use '?' at the end of the function name to display its documentation.
11:36	So, we hope you have enjoyed this tutorial and found it useful.
11:39	Thank you!

Contributors and Content Editors

Devraj, Gaurav, Minal, PoojaMoolya, Sandhya.np14, Sneha