why b and c are different here?

Question

https://code.sololearn.com/c6kCfAzcJ9vV/?ref=app

Answer 1

The list for the default argument is only created once when the function is defined.

Whenever you don't pass an argument, the name will refer to the default object.

So it's the same one list every time, and it changes when you change it.

Answer 2

HonFu How many little secretes hidden behind python :-)