"isinstance" Integer Bug?

Scripting
,
1

Following snippet outputs “No”. Any ideas why? Can anyone replicate the problem.


number = 12345678901

if isinstance(number, int):
    print("Yes")
else:
    print("No")
2

You can also check this way:

def is_int(val):
    if type(val) == int:
        return "Yes"
    else:
        if val.is_integer():
            return "Yes"
        else:
            return "No"
3

Try this:

number = 12345678901

if isinstance(number, (int, long)):
    print("Yes")
else:
    print("No")
1 Like
4

This is about precision of the integer types in Ironpython. In your example, number is defined as an instance of type long (long integer) because it exceeds the system 32-bit precision limit. More info about this here. You can see this with by print type(number). A way to check for either integer types (int and long) would be simply

number = 12345678901
if isinstance(number, (int,long)):
    print("Yes")
else:
    print("No")
1 Like
5

Thank you Mostapha and David,

I wrongly assumed that all IronPython integers are implemented as long (as in Python).

6

I wrongly assumed that all IronPython integers are implemented as long (as in Python).

Hi,
A finickity point - It’s not just Ironpython : This was the case in CPython 2.7 as well. It was changed a decade ago with the move to Python 3 :slight_smile:

https://docs.python.org/2/library/stdtypes.html

7

Make sure you don’t mix C long with Python long. Plain integers (int) in Python are implemented with C long, but are still called integers. Python long has no limit (other than what fits in memory).