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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+2 at 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