IPython¶

IPython is a console program that extends the regular Python interpreter: among others, one can directly run scripts and re-use output.

Want to see a video?

Here are some videos on IPython:

After loading a Python module, you also have the IPython Python command shell available.

Forgot how to load a Python module?

See the UPPMAX page about Python here.

What is a Python command shell?

In computing, a shell is a a program around something, for example, Bash is a shell around a UNIX-like operating system.

In computing, a command shell means that the shell is a command-line shell, i.e. text only.

A Python command shell, hence, is a text-only program around Python.

Start the IPython command shell by typing:

ipython

or (for explicit Python 3):

ipython3

The ipython3 prompt looks like this:

[sven@rackham1 ~]$ ipython
Python 3.11.4 (main, Aug  7 2023, 16:05:58) [GCC 12.2.0]
Type 'copyright', 'credits' or 'license' for more information
IPython 8.14.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]:

IPython allows one to write code interactively.

For example, in IPython, type:

print('Hello, world!')

and IPython will show the result of that line of code.

IPython can interact with your file system.

How does IPython interact with the file system?

For example, within IPython, running ...

```python ls ````

... displays a list of files in your current working folder in the same way as Bash's ls.

The Python interpreter will give an error if you do the same.

IPython has an auto-complete triggered by Tab.

How do I get auto-complete?

As an example, writing this line of code in IPython ...

s = 'Hello, world!'

... and press enter. Now a variable called s will hold some text.

Now type ...

s.

and press Tab. You will see a menu of things you can do with that string. Hold tab to scroll through the many options.

IPython can show graphics.

How do I get IPython to show graphics?

In IPython, run this code line-by-line:

import matplotlib.pyplot as plt
plt.plot([1, 2, 3, 4])
plt.show()

(or as a one-liner: import matplotlib.pyplot as plt; plt.plot([1, 2, 3, 4]); plt.show())

You will see a window appear:

A window with the plot

You will only see a window appear, if you've logged in to Rackham with SSH with X forwarding enabled.

Spoiler to login: ssh -X sven@rackham.uppmax.uu.se.

Spoiler to confirm: run xeyes.

IPython can directly run scripts.

How do I get IPython to directly run scripts?

In IPython, run:

run [filename]

where [filename] is the name of a file, for example:

run my_script.py

IPython will run the script and remember variables, functions and classes created in that script.