Python 2.x gotchas and landmines

Question

The purpose of my question is to strengthen my knowledge base with Python and get a better picture of it, which includes knowing its faults and surprises. To keep things sp

Answer 1

One of the biggest surprises I ever had with Python is this one:

a = ([42],)
a[0] += [43, 44]

This works as one might expect, except for raising a TypeError after updating the first entry of the tuple! So a will be ([42, 43, 44],) after executing the += statement, but there will be an exception anyway. If you try this on the other hand

a = ([42],)
b = a[0]
b += [43, 44]

you won't get an error.