Le 14/09/2019 à 04:26, Oscar Benjamin a écrit :
I've been staring at this for a little while:
from itertools import product
class Naturals:
def __iter__(self):
i = 1
while True:
yield i
i += 1
N = Naturals()
print(iter(N))
print(product(N)) # <--- hangs
When I run the above the call to product hangs but I can't see why. I
would expect that since I'm not iterating over the product it would
just call iter(N) but clearly not since iter(N) returns a generator
instantly where as product(N) hangs.
What am I missing?
Oscar
here is a pseudo code for product:
def product(*args, repeat=1):
# product('ABCD', 'xy') --> Ax Ay Bx By Cx Cy Dx Dy
# product(range(2), repeat=3) --> 000 001 010 011 100 101 110 111
pools = [tuple(pool) for pool in args] * repeat
result = [[]]
for pool in pools:
result = [x+[y] for x in result for y in pool]
for prod in result:
yield tuple(prod)
clearly "tuple(pool)" hangs with an infinite iterable pool
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