Run the following code:

a = a[0] = [0]
print(a)

Do you think it will error out on the first line? Can you explain how it works? Think about it, then read below for the answer:

Chained assignment in python takes the rightmost element and assigns
left to right, such that the statement boils down to:

tmp = [0]
a = tmp
a[0] = tmp

Thus creating a as a list of one element, that element being itself.

This is probably the most confusing and satisfyingly evil python trick I
know. Do you know other interesting tricks?
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