Let me share a secret.

I do not like Python.

It is not a programmer's programming language.

It is a getting-things-done language.

60's Brutalist architecture in Moscow in the 90's.


It is not just ugly, the heating doesn't work.

Oh, and Winter is on the way.

Why Python?

As with every unfashionable city quarter, we can some interesting artsy things without paying too much in rent.

But before we get started, let's setup our workspace.


Install the Python programming language on your system.

Google the previous sentence for instructions.

Second let's create and run a Python script.

Create a text file called foo.py.

Open it in a text editor and type,

a = lambda: 42


Install iPython.

The 'i' stands for interactive. We will split our time between the iPython interactive shell and the text editor.

Now cd to the appropriate directory on your command line and run


Assuming our iPython shell started in the same directory as our foo.py file, we can import it

import foo as f

here we have given foo the alias f.

Let's test our code.

In (1): f.a()

Out(1): 42


When we tweak our code, it's best if iPython refreshes automatically, rather than running the import manually.

Find the iPython configuration file.

On my Linux machine it is located here:


Search for these variables and set up 'autoreload'

c.InteractiveShellApp.exec_lines = ['%autoreload 2']

c.InteractiveShellApp.extensions = [ 'autoreload' ]

Now import foo.py again. Try f.a() change it to 43 and call f.a() again, it should show 43.


What have we done?

We have created a 'lambda' function or 'mathematical' function, if you prefer, set it to 42 and named it 'a'.

We have begin to use Python's flavour of Lambda calculus.

If you are used to Python, Lambdas are terribly frustrating, because as a Python programmer you are undisciplined.

Lambdas are a lot of things, but most importantly, during our katas they will help us remain disciplined.