Python Asterisk and Slash Special Parameters

petr | 1. června 2024 3:06

You use a bare asterisk to define a boundary between arguments that you can pass by either position or keyword from those that you must pass by keyword. You use the slash to define a boundary between those arguments that you must pass by position from those that you can pass by either position or keyword. Here’s a visual that summarizes how to use these symbols:

 

>>> def asterisk_usage(either, *, keyword_only):
...     print(either, keyword_only)
...
>>> asterisk_usage(either="Frank", keyword_only="Dean")
Frank Dean

>>> asterisk_usage("Frank", keyword_only="Dean")
Frank Dean

>>> asterisk_usage("Frank", "Dean")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: asterisk_usage() takes 1 positional argument but 2 were given

 

>>> def slash_usage(positional_only, /, either):
...     print(positional_only, either)
...
>>> slash_usage("Frank", either="Dean")
Frank Dean

>>> slash_usage(positional_only="Frank", either="Dean")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: slash_usage() got some positional-only arguments
passed as keyword arguments: 'positional_only'

>>> slash_usage("Frank", "Dean")
Frank Dean

 

https://realpython.com/python-asterisk-and-slash-special-parameters/