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Questions:

• How can I run Python programs?

Objectives:

• Launch the Jupyter Notebook, create new notebooks, and exit the Notebook.
• Create Markdown cells in a notebook.
• Create and run Python cells in a notebook.

Keypoints:

• Python programs are plain text files.
• Use the Jupyter Notebook for editing and running Python.
• Use the keyboard and mouse to select and edit cells.
• The Notebook will turn Markdown into pretty-printed documentation.

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There are multiple ways to run Python code

• Python programmes can be written as plain text files using a text editor
• They have the .py extension to let everyone (including the operating system) know it is a Python program. This is convention, not a requirement. We will use plain text files for writing Python code towards the end of this course.
• For this part of the course we are going to use [Jupyter Notebooks][jupyter].
• The Notebook provides code completion and other helpful features.
• Notebook files have the extension .ipynb to distinguish them from plain-text Python programs.

You can use the Jupyter Notebook for editing and running Python.

• When we type jupyter notebook in a terminal (or Git Bash) we start a Jupyter Notebook server and open the default web browser.
• The server runs locally on your machine only and does not use an internet connection.
• You can type code into the browser and see the result when the web page talks to the server.
• This has several advantages:
  • You can easily type, edit, and copy and paste blocks of code.
  • Tab complete allows you to easily access the names of things you are using and learn more about them.
  • It allows you to annotate your code with links, different sized text, bullets, etc. to make it more accessible to you and your collaborators.
  • It allows you to display figures next to the code that produces them to tell a complete story of the analysis. The notebook file is stored in a format called JSON.
  • Just like a webpage, what's saved looks different from what you see in your browser.
  • But this format allows Jupyter to mix source code, text, and images, all in one file.

Tip: You can view this page as a Notebook by clicking on either the Binder or Colab button at the top of this page.

Use the keyboard and mouse to select and edit cells.

• You can create a new cell by clicking on Insert at the top of the Notebook.
• Pressing the "shift" and the "enter" key together will execute the contents of the cell.

Use command mode to speed things up

• You can also use keyboard shortcuts by entering command mode using the esc key.
• Notice that the border of your cell turns blue.
• Type a shortcut command - for example b to create a new cell.
• The list of shortcuts can be found using h.
• To exit command mode and start editing the cell press enter.

The Notebook will turn Markdown into pretty-printed documentation.

• Notebooks can also render [Markdown][markdown] which is a simple plain-text format for writing lists, links, and other things that might go into a web page.
• You can turn cell into a Markdown cell by selecting Markdown from the drop-down menu at the top of the Notebook
• In [ ]: will disappear to show it is no longer a code cell and you will be able to write in Markdown.

Lists

    *   Use asterisks
    *   to create
    *   bullet lists.

• Use asterisks
• to create
• bullet lists.

1.  Use numbers
2.  to create
3.  numbered lists.

1. Use numbers
2. to create
3. numbered lists.

1.  You can
2.  also
    * create sub-lists

1. You can
2. also
   • create sub-lists

Headings

# A Level-1 Heading

A Level-1 Heading

## A Level-2 Heading (etc)

A Level-2 Heading (etc)

Whitespace

Line breaks
don't matter.

But blank lines
create new paragraphs.

Line breaks don't matter.

But blank lines create new paragraphs.

Basic formatting

You can easily:

• use italics with *italics*
• use bold with **bold**
• Create links with [...](...).

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Do the quick-test.

Back to Python part one.

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