Infinite for loops possible in Python?

Is it possible to get an infinite loop in for loop?

My guess is that there can be an infinite for loop in Python. I'd like to know this for future references.

Solution 1:

You can use the second argument of iter(), to call a function repeatedly until its return value matches that argument. This would loop forever as 1 will never be equal to 0 (which is the return value of int()):

for _ in iter(int, 1):
    pass

If you wanted an infinite loop using numbers that are incrementing you could use itertools.count:

from itertools import count

for i in count(0):
    ....

Solution 2:

The quintessential example of an infinite loop in Python is:

while True:
    pass

To apply this to a for loop, use a generator (simplest form):

def infinity():
    while True:
        yield

This can be used as follows:

for _ in infinity():
    pass

Solution 3:

Yes, use a generator that always yields another number: Here is an example

def zero_to_infinity():
    i = 0
    while True:
        yield i
        i += 1

for x in zero_to_infinity():
    print(x)

It is also possible to achieve this by mutating the list you're iterating on, for example:

l = [1]
for x in l:
    l.append(x + 1)
    print(x)