Relative import happens whenever you are importing a package relative to the current script/package.
Consider the following tree for example:
mypkg ├── base.py └── derived.py
derived.py requires something from
base.py. In Python 2, you could do it like this (in
from base import BaseThing
Python 3 no longer supports that since it’s not explicit whether you want the ‘relative’ or ‘absolute’
base. In other words, if there was a Python package named
base installed in the system, you’d get the wrong one.
Instead it requires you to use explicit imports which explicitly specify location of a module on a path-alike basis. Your
derived.py would look like:
from .base import BaseThing
. says ‘import
base from module directory’; in other words,
.base maps to
Similarly, there is
.. prefix which goes up the directory hierarchy like
..mod mapping to
../mod.py), and then
... which goes two levels up (
../../mod.py) and so on.
Please however note that the relative paths listed above were relative to directory where current module (
derived.py) resides in, not the current working directory.
Explanation about the star import case
For example, you need to use a few
math functions but you use them only in a single function. In Python 2 you were permitted to be semi-lazy:
def sin_degrees(x): from math import * return sin(degrees(x))
Note that it already triggers a warning in Python 2:
a.py:1: SyntaxWarning: import * only allowed at module level def sin_degrees(x):
In modern Python 2 code you should and in Python 3 you have to do either:
def sin_degrees(x): from math import sin, degrees return sin(degrees(x))
from math import * def sin_degrees(x): return sin(degrees(x))