How can i move just Zero to the end of my list and not False in python

Question

def move_zeros(array):
    for element in array:
        if element == 0 and type(element) is not bool:
            array.append(array.pop(array.index(element)))
    return array

print(move_zeros([False,1,0,1,2,0,1,3,"a"]))

My result is [1, 1, 2, 1, 3, 'a', False, 0, 0] I don't want False to move, my program sees False as 0.

Answer 1

This is coming about because you're operating on the list while looping over it, as well as the issue that you've correctly identified, that False == 0 and 0 == 0 both are True in Python. One way to deal with this is the following, using is instead of == to check equality to 0:

def move_zeros(a):
    return [x for x in a if x is not 0] + [x for x in a if x is 0]

print(move_zeros([False,1,0,1,2,0,1,3,"a"]))

Output:

[False, 1, 1, 2, 1, 3, 'a', 0, 0]

Note that the use of is to compare integers is not safe in general because integers outside of the range (-5, 256) have different ids from each other (see this question). In our case however, we are just using 0, so the solution above is safe.

Answer 2

Simple solution and showing that your check is actually ok:

>>> sorted(array, key=lambda x: x == 0 and type(x) is not bool)
[False, 1, 1, 2, 1, 3, 'a', 0, 0]

Or compare with the False singleton:

>>> sorted(array, key=lambda x: x == 0 and x is not False)
[False, 1, 1, 2, 1, 3, 'a', 0, 0]

Or if you're feeling playful, chained comparisons:

>>> sorted(array, key=lambda x: 0 == x is not False)
[False, 1, 1, 2, 1, 3, 'a', 0, 0]