Question

How can a standard-library module (say math) be accessed when a file prog.py is placed in the same directory as a local module with the same name (math.py)?

I’m asking this question because I would like to create a package uncertainties that one can use as

import uncertainties
from uncertainties.math import *

Thus, there is a local math module inside the uncertainties directory. The problem is that I want to access the standard library math module from uncertainties/__init__.py.

I prefer not to rename uncertainties.math because this module is precisely intended to replace functions from the math module (with equivalents that handle numerical uncertainties).

PS: this question pertains to the module I wrote for performing calculations with uncertainties while taking into account correlations between variables.

Answer 1

You are looking for Absolute/Relative imports from PEP 328, available with 2.5 and upward.

In Python 2.5, you can switch import‘s behaviour to absolute imports using a from __future__ import absolute_import directive. This absolute- import behaviour will become the default in a future version (probably Python 2.7). Once absolute imports are the default, import math will always find the standard library’s version. It’s suggested that users should begin using absolute imports as much as possible, so it’s preferable to begin writing from pkg import string in your code.

Relative imports are still possible by adding a leading period to the module name when using the from … import form:

from __future__ import absolute_import
# Import uncertainties.math
from . import math as local_math
import math as sys_math