Checking type of big integer values without sign

Question

There is this code:

print isinstance(2147483647, int) # True - max signed 32-bit integer
print isinstance(4294967295, int) # False - max unsigned 32-bit integer
print isinstance(18446744073709551615, int) # False - max unsigned 64-bit integer

How to check if value is unsigned 32-bit integer and unsigned 64-bit integer?

Answer 1

If you just intended to check whether the number fits in a 32 bit integer or 64 bit integer, there is a method called bit-length which you can check and determine if the result is less than 32 or not.

For ex.

>>> def Is32or64(x):
    return 32 if x.bit_length() < 32 else 64

>>> Is32or64(2**30)
32
>>> Is32or64(2**40)
64 

Answer 2

You can not check for unsigned integer types because there are no unsigned integer types.

Python 2 has two types for integers: int (fixed range, platform dependent, 32-bit at least) and long (infinitely big integer). Both are signed.

In your example, the first value has type int and the other two are long. If you want to know if a value fits into range of 64-bit integer, do an ordinary comparison:

if (x >= 0) and (x < 2**64):
    pass

Starting with Python versions 2.7 and 3.1, there is int.bit_length() method which calculates how many bits a binary representation of the number has, ignoring the sign.