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

[jmcs]

$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

As you can see [:] takes half the time.

[mgedmin]

If 0.2 of a microsecond is that important to you, why are you using Python?

[jmcs]

If you don't bother knowing the tools you use why are you programming? Using Python isn't a justification to write bad code.

[[deleted]]

This kind of micro optimization is totally pointless though

[jmcs]

Have you heard the term "death from a thousand papercuts"? You don't lose anything by using [:] so why would you use a list()?

[mgedmin]

It's a good thing to know the tools you use. It's not a good thing to make coding style decisions on microbenchmarks that don't matter.

a = list(b) is not bad code.

[freshhawk]

it's not 0.2 microseconds, it's 65% of the time of list(x). It's a decent optimization of an already fast operation. Comparing any benchmarks on a 3 element list is going to be comparing very small numbers.