integer - How does Python manage int and long?

Question

Does anybody know how Python manage internally int and long types?

• Does it choose the right type dynamically?
• What is the limit for an int?
• I am using Python 2.6, Is is different with previous versions?

How should I understand the code below?

>>> print type(65535)
<type 'int'>
>>> print type(65536*65536)
<type 'long'>

Update:

>>> print type(0x7fffffff)
<type 'int'>
>>> print type(0x80000000)
<type 'long'>

Answer 1

int and long were "unified" a few versions back. Before that it was possible to overflow an int through math ops.

3.x has further advanced this by eliminating long altogether and only having int.

• Python 2: sys.maxint contains the maximum value a Python int can hold.
  • On a 64-bit Python 2.7, the size is 24 bytes. Check with sys.getsizeof().
• Python 3: sys.maxsize contains the maximum size in bytes a Python int can be.
  • This will be gigabytes in 32 bits, and exabytes in 64 bits.
  • Such a large int would have a value similar to 8 to the power of sys.maxsize.