Let's talk about the problem with mutable default argument values in Python.
Function arguments in Python can have default values.
For example this greet function's name argument has a default value:
This is a premium screencast available only to active Python Morsels subscribers.
Feel free to watch some of the free screencasts in the Functions series.
Need to fill-in gaps in your Python skills? I send weekly emails designed to do just that.
As of Python 3.8, it's possible to declare positional-only arguments when defining a function. You'll (likely) rarely use this feature, but knowing it is handy for deciphering cryptic documentation.