Re-using Zip Iterator In Python 3
Solution 1:
If you were to create a generator each time you loop, that would solve everything, because you could reuse that multiple times. For that, convert L_RANGES from a simple generator to a lambda creating generators, but don't forget to "call" it each time with ():
L_RANGES = lambda: zip(range(10, 20), range(11, 21))
for a, b in L_RANGES():
print(a, b)
for a, b in L_RANGES():
print(a, b)
#works as many times as you wantCompared to the other answers this doesn't take up memory (which is the downside of converting to a list) and doesn't require multiple variables for each time you want to loop (by using tee) which makes this way more flexible (you can iterate 1000 times if necessary, without creating L_RANGES_1...L_RANGES_999) for example:
for i in range(1000):
for a, b in L_RANGES():
print(a, b)
Solution 2:
An iterator, once exhausted, may not be reused. In Python 3.x, zip returns an iterator. One solution is to use itertools.tee to copy an iterator n times.
For example, setting n = 2, we can do the following:
from itertools import tee
L_RANGES_1, L_RANGES_2 = tee(zip(range(10, 20), range(11, 21)), 2)
for item in L_RANGES_1:
# do somethingfor item in L_RANGES_2:
# do something elseConversion to a list allows use an arbitrary number of times, but is inadvisable for large iterables due to the memory overhead.
For a large number of copies, you can use a dictionary. For example:
L_RANGES = dict(zip(range(1000), tee(zip(range(10, 20), range(11, 21)), 1000)))
Solution 3:
In Python 3.x zip() returns iterator that gets exhausted.
Simplest way to avoid it is:
L_RANGES = list(zip(range(10, 20), range(11, 21)))
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