Transcript
NARRATOR
In this screencast I'm going to introduce you to Jupyter Notebooks. First you'll need to start the Anaconda launcher. This screencast was done on a Mac. However, the same process applies to Windows. If you're a Linux user, you'll need to use the command line as described in the installation instructions. To follow along on your computer, make sure you have created a folder for this course, and that it contains the exercise notebook for this week. This screencast uses earlier versions of the exercise notebook, and of the Anaconda software than you downloaded, so don't worry that things look slightly different.
Do not click on 'Update' buttons in the Anaconda Launcher, because you should use the version you installed to avoid compatibility problems with the notebooks of this course. Once the Anaconda launcher has booted up, launch the ipython notebook. Whenever you see a circle, the mouse has been clicked. After a couple of screens you should see Jupyter running in a browser, and the contents of your home folder. Navigate to the folder you created, and open the relevant notebook. The first thing to appreciate is that Jupyter notebook consists of a sequence of individual cells. You can see the individual cells as I click on the left of each one. Each cell can contain text or code.
Before starting any exercises, you should execute all the code already in the notebook. I'll explain why in a moment. Go to the 'Cell' menu and select 'Run all'. As the notebook executes all code, it may automatically scroll to a different part of the notebook. Just scroll back to the start. Go to the first exercise. It asks you to add assignments for more countries into the preceding code cell. To select a cell, click to the left of it. A grey border shows the currently selected cell. To edit a cell, click inside it. The border becomes green to show the cell is in editing mode.
Once inside the cell press 'Enter' a couple of times to put the cursor on a new line, then start typing an appropriate variable name, say 'deaths in Russia'. Once you've start typing, names that have been used within the notebook can be accessed via the Tab key. So once you've typed 'de' press the Tab key to get some auto-complete suggestions. Use the arrow keys to scroll through the options and press 'Enter' to select the appropriate option. In this case I'll accept the first suggestion in the list and edit it to complete the assignment. Next start a new line and just enter the new variable name you've just added. Remember to use auto-complete to avoid spelling mistakes.
Now we can run the code. To execute only the current code cell, click on the 'Play' button. The results appear below the code cell in a line titled 'Out'. If you wish to split a cell, for example to separate the supplied code from the code you are adding, then put the cursor where you want to split the cell, go to the 'Edit' menu and select 'Split Cell'. It's easy to move cells around - for example we can cut a selected cell......and then paste it below another cell that you select. To save a snapshot of the notebook, called a checkpoint, click the 'Save and Checkpoint' button.
If things go horribly wrong, you can revert the notebook to the last checkpoint by using the 'Revert to Checkpoint' option in the 'File' menu. To finish your session, go to the 'File' menu and select 'Close and Halt'. It is very important to note that opening a notebook does not execute any code cells. Any code output was saved from the previous session. So if I reopen the workbook and execute the code in the second cell alone, I'll get an error, because in this session (that is since the notebook was opened again) the first cell hasn't been executed and therefore the computer doesn't recognise the variable name 'deaths in Portugal'. And that's why you should run all code after opening a notebook!
It's easy to add your own notes to the notebook. For example if I select the first cell......and then click on the plus button, I can insert a new cell below the current one. By default, a new cell is a code cell. Select 'Markdown' to change it to a text cell. To edit a text cell, double-click inside the cell. Text is written in Markdown, a very simple formatting system. Here are some examples of what Markdown can do - pay attention to how prefixing or surrounding words with simple characters is all the information needed to format the text.
Also note the way a word or phrase to be hyperlinked is surrounded with square brackets and immediately followed by the URL, in round brackets. Once the text is written, click the 'Play' button to see the formatted text in the cell. The 'Help' menu contains links to information about Jupyter notebooks and Markdown formatting. As you get used to Jupyter, take a look at the keyboard shortcuts, as they will help you to work more efficiently.