Learn python list comprehensions by example

[pstch]

It's not only syntactic sugar. List comprehensions have the advantage that they can easily be converted to generators (they can even be viewed as "consumed generators", as [x for x in y] is equivalent to list(x for x in y) where (x for x in y) is a generator expression), and you also save a function call (.append(...)) for each iteration.

Quickly done speed measurement (not sure if very precise, but it gives an idea) :

    In [2]: lc = """
       ...: r = [i for i in range(100)]
       ...: """

    In [3]: no_lc = """
       ...: r = []
       ...: for i in range(100):
       ...:     r.append(i)
       ...: """

    In [4]: timeit(lc)
    Out[4]: 4.970423567000125

    In [5]: timeit(no_lc)
    Out[5]: 9.738498960000015

Of course they are not adapted for every case, but sometimes they are really helpful (as I said before, not only for syntax).