integer – How does Python manage int and long?

integer – How does Python manage int and long?

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.

This PEP should help.

Bottom line is that you really shouldnt have to worry about it in python versions > 2.4

integer – How does Python manage int and long?

Python 2 will automatically set the type based on the size of the value. A guide of max values can be found below.

The Max value of the default Int in Python 2 is 65535, anything above that will be a long

For example:

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

In Python 3 the long datatype has been removed and all integer values are handled by the Int class. The default size of Int will depend on your CPU architecture.

For example:

  • 32 bit systems the default datatype for integers will be Int32
  • 64 bit systems the default datatype for integers will be Int64

The min/max values of each type can be found below:

  • Int8: [-128,127]
  • Int16: [-32768,32767]
  • Int32: [-2147483648,2147483647]
  • Int64: [-9223372036854775808,9223372036854775807]
  • Int128: [-170141183460469231731687303715884105728,170141183460469231731687303715884105727]
  • UInt8: [0,255]
  • UInt16: [0,65535]
  • UInt32: [0,4294967295]
  • UInt64: [0,18446744073709551615]
  • UInt128: [0,340282366920938463463374607431768211455]

If the size of your Int exceeds the limits mentioned above, python will automatically change its type and allocate more memory to handle this increase in min/max values. Where in Python 2, it would convert into long, it now just converts into the next size of Int.

Example: If you are using a 32 bit operating system, your max value of an Int will be 2147483647 by default. If a value of 2147483648 or more is assigned, the type will be changed to Int64.

There are different ways to check the size of the int and its memory allocation.
Note: In Python 3, using the built-in type() method will always return <class int> no matter what size Int you are using.

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