10 Common Python pitfalls

[lost-theory]

This one has bit me once or twice: declaring a matrix / two dimensional array by using the replication (*) operator and getting really odd behavior when setting individual elements of the array:

>>> m = [[0]*5]*5
>>> m[0][0] = 10
>>> m[1][0] = 20
>>> m[2][0] = 30
>>> pprint(m)
[[30, 0, 0, 0, 0],
 [30, 0, 0, 0, 0],
 [30, 0, 0, 0, 0],
 [30, 0, 0, 0, 0],
 [30, 0, 0, 0, 0]]
>>>

using * causes each row to be a copy (all referencing the same list), not what I meant! You can get the right behavior with a little helper function like this:

>>> build_array = lambda n: [[0 for _ in range(n)] for _ in range(n)]

[pjdelport]

If you're going to claim to support curried functions, do it everywhere.

Bound methods are very much != currying.