for（i = 0; True; i ++）在python中？

Question

是否有更多的pythonic方式，或者至少更短更简单的方法来执行此操作：

i = 1
while True:
    res = lookup(i) # returns a value or None
    if res is None:
        break
    else:
        i += 1
        yield res

Answer 1

您可以使用itertools：

from itertools import takewhile, count

# ...
def myfunc():
    return takewhile(lambda x: x is not None, (lookup(i) for i in count(1)))

如果您因任何原因不喜欢takewhile：

for i in count(1):
     res = lookup(i)
     if res is None: break
     yield res

Answer 2

不进入itertools ...

i = 1
res = lookup(i)
while res is not None:
    i += 1
    yield res
    res = lookup(i)

Answer 3

itertools.count可以无限期地计算：

for i in itertools.count(1):
    res = lookup(i)
    if res is None: break
    yield res