Star (*) as a parameter in python function [duplicate]

The * indicates the end of the positional arguments. Every argument after that can only be specified by keyword. This is defined in PEP 3102

>>> def foo1(a, b=None):
...     print(a, b)
...
>>> def foo2(a, *, b=None):
...     print(a, b)
...
>>> foo1(1, 2)
1 2
>>> foo2(1, 2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: foo1() takes 1 positional argument but 2 were given
>>> foo2(1, b=2)
1 2