如何确定Python中的数字是32位还是64位整数？

Question

I want to differentiate between 32-bit and 64-bit integers in Python. In C it's very easy as we can declare variables using int_64 and int_32 . But in Python how do we differentiate between 32-bit integers and 64-bit integers?

Answer 1

There's no need. The interpreter handles allocation behind the scenes, effectively promoting from one type to another as needed without you doing anything explicit.

Answer 2

Basically, you don't. There's no reason to. If you want to deal with types of known bit size, look at numpy datatypes.

If you want to put data into a specified format, look at the struct module.

Answer 3

The struct module mentioned in the other answers is the thing you need.

An example to make it clear.

import struct

struct.pack('qii', # Format string  here.
            100, # Your 64-bit integer
            50, # Your first 32-bit integer
            25) # Your second 32-bit integer

# This will return the following:
'd\x00\x00\x00\x00\x00\x00\x002\x00\x00\x00\x19\x00\x00\x00'

documentation for the formatting string.

Answer 4

The following snippet from an ipython interpreter session indicates one way of testing the type of an integer. Note, on my system, an int is a 64-bit data type, and a long is a multi-word type.

In [190]: isinstance(1,int)
Out[190]: True    
In [191]: isinstance(1,long)
Out[191]: False    
In [192]: isinstance(1L,long)
Out[192]: True

Also see an answer about sys.getsizeof . This function is not entirely relevant, since some additional overhead bytes are included. For example:

In [194]: import sys    
In [195]: sys.getsizeof(1)
Out[195]: 24
In [196]: sys.getsizeof(1L)
Out[196]: 28