如何使用 Python 检查数字是否为 32 位 integer？

Question

In my program I'm looking at a string and I want to know if it represents a 32-bit integer.

Currently I first check if it is a digit at all using isdigit() , then I check if it exceeds the value of 2^32 (assuming I don't care about unsigned values).

What's the best way to check that my input string contains a valid 32-bit integer?

Answer 1

Assuming the largest 32-bit integer is 0xffffffff ,

Then, we need to check if our number is larger than this value:

abs(n) <= 0xffffffff

Wrapping an abs() around the number will take care of negative cases, too.

Answer 2

Just another idea, see if the value can be packed in a 4 bytes:

>>> from struct import pack, error
>>> def test_32bit(n):
...     try:
...             pack("i", n)
...     except error:
...             return False
...     return True
... 

If working with unsigned values, pack("I", n) instead.

Answer 3

>>> def is_int32(number):
...     try:
...         return not(int(number)>>32)
...     except ValueError:
...         return False

Answer 4

For unsigned values, this will work:

>>> def is32(n):
...     try:
...         bitstring=bin(n)
...     except (TypeError, ValueError):
...         return False
...         
...     if len(bin(n)[2:]) <=32:
...         return True
...     else:
...         return False    
... 
>>> is32(2**32)
False
>>> is32(2**32-1)
True
>>> is32('abc')
False

Answer 5

The easy solution will be like this

if abs(number) < 2**31 and number != 2**31 - 1:
   return True
else:
   return False

If our number in [−2^31, 2^31 − 1] range we are good to go

Answer 6

>>> def is_32_bit(n: int) -> bool: ... if n in range(-2 ** 31, (2**31) - 1): ... return True ... return False ... >>> is_32_bit(9999999999) False >>> is_32_bit(1) True

Answer 7

We can use left shift operator to apply the check.

def check_32_bit(n):
    return n<1<<31

Answer 8

Found answer here: https://docs.python.org/2/library/stdtypes.html#int.bit_length

Simplest and most effective solution I think

>>> your_num = 2147483651
>>> your_num.bit_length()
32