Help understanding code

[Mekire]

So, nasty recursive code with part of it wrapped in a list comp... wonderful.

Let's try breaking that line up:

power_set(l[1:]) + [[l[0]] + x for x in power_set(l[1:])]

We have:

power_set(l[1:])

and

[[l[0]] + x for x in power_set(l[1:])]

The first part is easy.  power_set(l[1:]) is the powerset of the current sequence without the first entry.
So if you ask for the power set of [1,2,3,4] it gives the power set of [2,3,4].

The second part is the first character in the sequence + the previous expression.
So if you ask for the powerset of [1,2,3,4] it gives you [1] + each set in the powerset of [2,3,4].


So to try once again to put this into words:
""" The powerset of any sequence is equal to (the powerset of the sequence without the first entry) + (the first entry +  (each set in the powerset of the sequence without the first entry))."""

Not sure if that is any clearer.  I tried. =P