Assuming you're using python 3.X, everything the user inputs will be a string. Even numbery looking things like "23" or "0". int(thing) doesn't validate that thing is of the integer type. It attempts to convert thing from whatever type it is now, into the integer type, raising a ValueError if it's impossible.

Demonstration:

>>> while True:
...     x = input("Enter something: ")
...     print("You entered {}".format(x))
...     print("That object's type is: {}".format(type(x)))
...
Enter something: hi
You entered hi
That object's type is: <class 'str'>
Enter something: hi46
You entered hi46
That object's type is: <class 'str'>
Enter something: 
You entered
That object's type is: <class 'str'>
Enter something: ]%$
You entered ]%$
That object's type is: <class 'str'>
Enter something: 23
You entered 23
That object's type is: <class 'str'>
Enter something: 42
You entered 42
That object's type is: <class 'str'>
Enter something: 0
You entered 0
That object's type is: <class 'str'>

input (in Python 2.any) will return the type of whatever expression the user types in. Better (in Python 2.any) is to use raw_input, which returns a string, and do the conversion yourself, catching the TypeError if the conversion fails.

Python 3.any's input works like 2.any's raw_input, i.e., it returns a string.