问题
I want to iterate a large number such as 600851475143 using the range() function in Python. But whenever I run the program it gives me an OverflowError. I have used the following code -
um = long(raw_input())
for j in range(1,num):
....
I have tried it many times but it is not working!
回答1:
Use itertools.islice() if your indices are long numbers:
from itertools import islice, count
islice(count(start, step), (stop-start+step-1+2*(step<0))//step)
Python 3's range() can handle python longs as well.
Simplified to your case:
for j in islice(count(1), num - 1):
回答2:
Although xrange seems to achieve what you want, it can't handle numbers that large. You may need to use this recipe from here
CPython implementation detail: xrange() is intended to be simple and fast. Implementations may impose restrictions to achieve this. The C implementation of Python restricts all arguments to native C longs (“short” Python integers), and also requires that the number of elements fit in a native C long. If a larger range is needed, an alternate version can be crafted using the itertools module:
islice(count(start, step), (stop-start+step-1+2*(step<0))//step).
回答3:
don't use for, use while
counter = long(1)
while counter < num:
...
来源：https://stackoverflow.com/questions/15725506/how-do-i-iterate-over-large-numbers-in-python-using-range