As for StackOverflow links provided by Robert, it looks to me that float.is_integer() is always used improperly.

If keep this method it would be worth to warn against improper use of it.

Bad:

    (x/5).is_integer()

Good:

    x % 5 == 0

or

    not x % 5

Bad:

    math.sqrt(x).is_integer()

Good:

    int(math.sqrt(x))**2 == x

Bad:

    while x < y:
        if x.is_integer():
            print(x)
        x += 0.1

Good (if initial x was integer):

    x0 = x
    i = 0
    while x < y:
        x = x0 + i/10
        if not i % 10:
            print(x)
        i += 1

And provide an example of a *proper* use case (if it exists).