Python override 3rd party package single file

What is the best way to override python any 3rd party package single file?

Suppose.

I have a package called foo. Foo contains file tar.py which have an import line.

tar.py

from xyz import abc
# some code

how do I replace that single line import

# from 
from xyz import abc
# to 
from xyz.xy import abc

i want to change this line outside virtualenv in python project

from Python override 3rd party package single file