What is the difference between range and xrange functions in Python 2.X?
显然xrange更快，但我不知道为什么它更快（除了迄今为止的轶事更快），或者除此之外还有什么不同
for i in range(0, 20):
for i in xrange(0, 20):
range creates a list, so if you do range(1, 10000000) it creates a list in memory with 9999999 elements.
xrange is a sequence object that evaluates lazily.
It should be added from @Thiago's hint, that in python3, range does the equivalent of python's xrange
range creates a list, so if you do range(1, 10000000) it creates a list in memory with 9999999 elements.
xrange is a generator, so it is a sequence object is a that evaluates lazily.
This is true, but in Python 3, range will be implemented by the Python 2 xrange(). If you need to actually generate the list, you will need to do:
list(range(1,100))
Remember, use the timeit module to test which of small snipps of code is faster!
$ python -m timeit 'for i in range(1000000):' ' pass'
10 loops, best of 3: 90.5 msec per loop
$ python -m timeit 'for i in xrange(1000000):' ' pass'
10 loops, best of 3: 51.1 msec per loop
Personally, I always use range(), unless I were dealing with really huge lists -- as you can see, time-wise, for a list of a million entries, the extra overhead is only 0.04 seconds. And as Corey points out, in Python 3.0 xrange will go away and range will give you nice iterator behaviour anyway.
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