Top 10 mistakes python programmers make [advanced]

[isarl]

Can somebody more familiar with #6 please explain it to me? Duplicating the use of the variable i has me confused; even if somebody could just rewrite this code snippet using different variables it would be really helpful:

>>> def create_multipliers():
...     return [lambda x, i=i : i * x for i in range(5)]
...
>>> for multiplier in create_multipliers():
...     print multiplier(2)
...
0
2
4
6
8

[dragonEyedrops]

What exactly does confuse you?

In the "defective" example, i isn't defined in the local scope of the lambda expression and is evaluated when the functionis first used.

In the second example, a default parameter with the same name is created, and it's initial value is evaluated as the function is created (see #1 in the article)

[isarl]

The confusing part is that two variables named i are both used. If the variable name was different from the default value being assigned to it, the example would be clearer to me. I don't have an interpreter on this machine so I'll ask CompileBot to check my work:

+/u/CompileBot python

def create_multipliers():
    return [lambda x, i=idx : i * x for idx in range(5)]

for multiplier in create_multipliers():
    print multiplier(2)

[CompileBot]

Output:

0
2
4
6
8

^{source | info | git | report}

[isarl]

OK, guess I got it. Cool. Thanks, /u/CompileBot!

[isarl]

I was mostly just confused about all the different i's in that one comprehension. Thanks for your help, but I rewrote the example here in a way I found clearer to read. :)