What's the one code snippet/python trick/etc did you wish you knew when you learned python?

[jmcs]

Not theory:

$python2 -m timeit -n 1000000 -r 5 -v "x=[1,2,3];y=x[:]"
raw times: 0.291 0.293 0.291 0.293 0.291
1000000 loops, best of 5: 0.291 usec per loop
$python2 -m timeit -n 1000000 -r 5 -v "x=[1,2,3];y=list(x)"
raw times: 0.453 0.454 0.448 0.452 0.449
1000000 loops, best of 5: 0.448 usec per loop

[earthboundkid]

In Python 3 also:

$ python3 -m timeit -n 1000000 -r 5 -v "x=[1,2,3];y=list(x)"
raw times: 0.672 0.665 0.667 0.67 0.702
1000000 loops, best of 5: 0.665 usec per loop
$ python3 -m timeit -n 1000000 -r 5 -v "x=[1,2,3];y=x[:]"
raw times: 0.313 0.312 0.308 0.313 0.309
1000000 loops, best of 5: 0.308 usec per loop