Question

IMO python is pass by value if the parameter is basic types, like number, boolean

func_a(bool_value):
    bool_value = True

Will not change the outside bool_value, right?

So my question is how can I make the bool_value change takes effect in the outside one(pass by reference?

Answer 1

You can use a list to enclose the inout variable:

def func(container):
    container[0] = True


container = [False]
func(container)
print container[0]

The call-by-value/call-by-reference misnomer is an old debate. Python’s semantics are more accurately described by CLU’s call-by-sharing. See Fredrik Lundh’s write up of this for more detail:

• Call By Object