Python for loop range (bigint)

Question

There is some short way in Python to do something like

"for i in range (n)"

when is n too large for Python to actually create an array range (n)?

(short, because otherwise I would just use a while loop)

Answer 1

You can use xrange () ... although this is limited to "short" integers in CPython:

CPython: xrange() . . Python C longs ( "" Python), , C . , itertools: takewhile(lambda x: x<stop, (start+i*step for i in count())).

, ( ), ...

, bigint , , , - , , xrange , , range.

Answer 2

: .

def gen():
    i = 0
    while 1: # or your special terminating logic
        yield i
        i = i + 1


for j in gen():
    do stuff

Answer 3

You can upgrade to python3. There, the range is not limited to “short” integers.

Another workaround would be to use xrange for small integers and add them to some constant inside the loop, for example.

offset, upperlimit = 2**65, 2**65+100
for i in xrange(upperlimit-offset):
    j = i + offset
    # ... do something with j

Answer 4

you should always use xrange, not the range, in order to just loop n times more than sth., but keep in mind that xrange also has a limit (if it's too small, you need to make your own while loop with a counter)

EDIT: too late ...