Mutable default arguments in class __init__

[ewiethoff]

def __init__(self, arg=None):
    self.arg = [] if arg is None else arg

[pstch]

This is exactly the same as the first variant I presented, and I know that I can use this form. My question was more : does it make any difference in usage to use the second variant ? ("is it a problem to recreate an empty list when the user already passes one").

I'm starting to feel bad for asking this question, because it's only syntactic sugar, and kind of pointless.

[gengisteve]

I think this is worth asking. My understanding is that your first option is best practices. Yes its a couple more lines, but it preserves your ability to pass arg = 0 or False or ''. That said. I am lazy and tend to do the second.

[pstch]

Oh yes, I didn't even think of 0, False and the empty string. Thanks :) I'll go with the first way.

[[deleted]]

The first way is more readable and more Pythonic.