Related problems of functions in Python3

1. Indefinite parameters

2. Default parameters

The value of the default parameter is only assigned once when the function is defined

x =def spam (A, b=x):    print(A, b) spam (#  1# changing the value of x has no effect on the default parameter value # 1

The value of the default parameter should be an immutable object, such as None, True, False, number, or string

def # Error [], {}, etc. as mutable objects

At this point, you can try none as the default value, and then check it in the function, giving the corresponding default value

def spam (A, b=none):    if is none:        = []

Related problems of functions in Python3