On 01/12/2014 07:40 PM, Keith Winston wrote:
Thanks Dave, that looks like a good idea, I've played a little with one-line generators (? the things similar to list comprehensions), but I'm still wrapping my head around how to use them.
You probably mean a generator *expression*. it's written like a list comprehension, bit with () instead of []. The semantic difference is that items are generated once at a time instead of all in one go and stored in a list. Another difference is that one cannot reuse such a generator object (once end is reached, it is like "empty").
spir@ospir:~$ python3 Python 3.3.1 (default, Sep 25 2013, 19:29:01) [GCC 4.7.3] on linux Type "help", "copyright", "credits" or "license" for more information.
l = [1,2,3] squares = [n*n for n in l] squares
[1, 4, 9]
for (i,sq) in enumerate(squares):
... print(i+1, sq) ... 1 1 2 4 3 9
squares = (n*n for n in l) squares
<generator object <genexpr> at 0x7f92496a7be0>
for (i,sq) in enumerate(squares):
... print(i+1, sq) ... 1 1 2 4 3 9
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