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
Now, your derived.py requires something from base.py. In Python 2, you could do it like this (in derived.py):
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
The leading . says ‘import base from module directory’; in other words, .base maps to ./base.py.
Similarly, there is .. prefix which goes up the directory hierarchy like ../ (with ..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.
@BrenBarn has already explained the star import case. For completeness, I will have to say the same ;).
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))
or:
from math import *
def sin_degrees(x):
return sin(degrees(x))