# future-import-boilerplate

Most Python files should include the following boilerplate at the top of the file, right after the comment header:

    from __future__ import (absolute_import, division, print_function)

This uses Python 3 semantics for absolute vs relative imports, division, and print. By doing this, we can write code which is portable between Python 2 and Python 3 by following the Python 3 semantics.

## absolute_import

When Python 2 encounters an import of a name in a file like `import copy` it attempts to load `copy.py` from the same directory as the file is in. This can cause problems if there is a python file of that name in the directory and also a python module in `sys.path` with that same name. In that case, Python 2 would load the one in the same directory and there would be no way to load the one on `sys.path`. Python 3 fixes this by making imports absolute by default. `import copy` will find `copy.py` from `sys.path`. If you want to import `copy.py` from the same directory, the code needs to be changed to perform a relative import: `from . import copy`.

See also

- Absolute and relative imports

## division

In Python 2, the division operator (`/`) returns integer values when used with integers. If there was a remainder, this part would be left off (aka, floor division). In Python 3, the division operator (`/`) always returns a floating point number. Code that needs to calculate the integer portion of the quotient needs to switch to using the floor division operator (//) instead.

See also

- Changing the division operator

## print_function

In Python 2, `print()` is a keyword. In Python 3, `print()` is a function with different parameters. Using this `__future__` allows using the Python 3 print semantics everywhere.

See also

- Make print a function