Python-3.4.3/C2/Getting-started-with-IPython/English-timed
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| 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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| 12:23 | This is Prabhu from IIT Bombay, signing off. Thanks for watching. |
