Python-3.4.3/C2/Getting-started-with-IPython/English-timed

Time	Narration
00:01	Hello friends. 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,
00:13	quit the IPython interpreter,
00:16	navigate the IPython session history,
00:20	use tab-completion within IPython,
00:23	look up documentation in IPython,
00:26	interrupt incomplete or incorrect commands.
00:30	To record this tutorial, I am using: Ubuntu Linux 14.04 operating system,
00:37	Python 3.5.2, IPython 5.1.0
00:44	What is IPython? IPython is an enhanced interactive Python interpreter.
00:50	It provides features like tab-completion and easier access to help.
00:56	Let us first see how to start the IPython interpreter.
01:00	First open the terminal by pressing Ctrl+Alt+T keys simultaneously on the keyboard.
01:07	Type ipython3 at the prompt and press Enter.
01:13	If IPython is not installed, please refer to the Instruction sheet.
01:18	If IPython is installed, the IPython interpreter is loaded by running the ipython command in the terminal.
01:25	The versions of Python and IPython that are installed, are shown on the terminal.
01:32	Some additional helpful information is printed by IPython.
01:37	After this, we get a prompt with i n bracket 1:
01:42	Now, let us see how we can quit the IPython interpreter. Press Ctrl+D keys.
01:48	A prompt will appear to confirm if we really want to exit.
01:53	Type y for yes and quit IPython.
01:57	Note that y is given in square brackets. So, it is default.
02:02	We could also press Enter and it will exit.
02:05	Else, type n for no if you don't want to quit IPython.
02:10	Let us type y. We have quit IPython interpreter and are back at the terminal prompt.
02:16	Let us start it again. Type ipython3 in the terminal and press Enter.
02:23	Now, let us learn how to use the interpreter. Let us start with the simplest operation - addition.
02:30	Type: 1 plus 2 at the IPython prompt and press Enter.
02:36	We press Enter to execute the python command. Please do so, after typing every command.
02:43	IPython promptly displays the output as 3.
02:47	Notice that the output is shown with an Out square brackets 1 indication.
02:54	Let us now try a few more operations such as- 5 minus 3, 7 multiplied by 4.
03:03	Each time we press Enter and see the output on the IPython console window.
03:10	Let us see how we can navigate to previous commands in IPython.
03:15	For example, say, we want to execute print open parenthesis 1 plus 2 close parenthesis.
03:23	Instead of typing the whole command, we can recall the command 1 plus 2 we typed earlier.
03:30	Use the up arrow key to go back to the command 1 plus 2.
03:35	Now use the left-arrow key to navigate to the beginning of the line.
03:40	Type the word print, open parenthesis close parenthesis, on the keyboard.
03:49	We have changed the command to print (1 plus 2). Now press Enter.
03:53	The interpreter prints the result as 3. Notice that this time, the indication Out square brackets, is not displayed.
04:03	Now let us execute print 10 multiplied by 2. We use the up arrow key to navigate to the previous command print (1 plus 2).
04:14	Now replace 1 plus 2 with 10 multiplied by 2 and press Enter.
04:21	As with any programming language, asterisk is used for multiplication operator.
04:27	Observe the output on the console.
04:30	Now, let us see, what is tab-completion. Let us consider an example.
04:35	Suppose we want to use the function "print".
04:39	For this, we just type pri at the prompt and press the tab key.
04:45	As you can see on the console that IPython has autocompleted the command pri to print.
04:52	This feature of IPython is called the tab-completion.
04:56	Let us see some more possibilities of tab completion. Just type p and then press the tab.
05:05	In this case, we see that IPython does not complete the command.
05:09	This is because, there are more than one command beginning with p.
05:14	Therefore, it just lists out all the possible tab-completions of p.
05:20	Now let us try out an exercise.
05:23	Pause the video, solve the problem and resume the video. Find out the commands starting with "ab".
05:31	List out the commands starting with "a".
05:35	ab autocompletes to a b s abs.
05:40	a tab displays a list of all the commands starting with a.
05:46	Now, let us see what the function abs is used for.
05:51	We will use the help feature of IPython to find out this.
05:55	To see the documentation of a function, type the function name followed by a question mark.
06:03	The IPython interpreter will show the documentation for the function.
06:08	From the displayed information, it says abs accepts a number as input and returns it's absolute value.
06:16	Let us see a few examples. On the console, type: a b s minus 19 and then a b s 19.
06:29	We get 19, as expected, in both the cases.
06:33	Now let us try it for decimal numbers. Let us try a b s minus 10.5.
06:42	We get 10.5 as the result.
06:46	Pause the video here. Try out the following exercise and resume the video.
06:52	Look-up the documentation of round and see how to use it.
06:57	Switch to the console for the solution. You can look up the documentation of the function round by typing round question mark.
07:06	It says here that the function 'round', rounds a number to a given precision.
07:12	ndigits is the precision value for round function. Notice, there are extra square brackets around ndigits.
07:21	This means that ndigits is optional and 0 is the default value.
07:27	Optional parameters are shown in square brackets in Python documentation.
07:33	Pause the video here. Try out the following exercise and resume the video.
07:38	Check the output of: round 2.48, round 2.48 comma 1, round 2.484, round 2.484 comma 2
07:52	We get round 2.48 is equal to 2.0,
07:57	round 2.48 comma 1 is 2.5,
08:02	round 2.484 is 2.0,
08:06	round 2.484 comma 2 is 2.48 which are what we expect.
08:13	Let us now see how to correct typing errors which we could make while typing on the console.
08:20	Let us make a typing error deliberately. Type: round open parenthesis 2.484 and press Enter, without closing the parenthesis.
08:32	We get a prompt with dots. This prompt is the continuation prompt of IPython.
08:40	It appears when the previous line is incomplete.
08:44	Now complete the command with close parenthesis and press Enter. We get the expected output, that is 2.
08:54	What if we type an incorrect command and end up with the continuation prompt?
09:00	In such case, we can press Ctrl+C keys to interrupt the command and get back to the IPython prompt.
09:09	round takes only numbers as input. Type: round(1a
09:15	Do not close the parenthesis and press Enter.
09:19	We gave alpha-numeric value '1 a' as input. Press Ctrl+C to interrupt the execution.
09:28	Pause the video here. Try out the following exercise and resume the video.
09:34	Type: round 2.484, without closing the parenthesis and press Enter.
09:41	Then cancel the command using Ctrl+C. Type the command round 2.484 comma 2
09:51	The output on your console should look like this.
10:01	This brings us to the end of this tutorial.
10:04	In this tutorial, we have learnt to: invoke the IPython interpreter by typing ipython in the terminal,
10:13	quit the IPython interpreter by using Ctrl+D,
10:17	navigate the IPython session history by using the arrow keys,
10:23	Use tab-completion to work faster,
10:27	see the documentation of functions using question mark,
10:32	interrupt commands using Ctrl+C when we make an error.
10:37	Here are some self assessment questions for you to solve.
10:41	IPython is a programming language similar to Python. True or False
10:46	Which key combination quits IPython? Ctrl + C Ctrl + D Alt + C Alt + D
10:55	Which character is used at the end of a command in IPython to display the documentation? under score question mark exclamation mark ampersand
11:07	And, the answers are- False. IPython is not a new programming language. It is just an enhanced interactive Python interpreter.
11:17	We use Ctrl + D to quit IPython interpreter.
11:21	We use question mark (?) at the end of the command to display its documentation.
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Contributors and Content Editors

PoojaMoolya, Sandhya.np14