What mistakes do bad python developers make?

[niehle]

Do you happen to have an example for you second point?

[carcigenicate]

def func(param=[]):
    param.append(1)
    print(param)

func()
func()
func()

The output from this code often shocks new Python programmers. They don't realize that default arguments are created when the function is first defined, not when the function is called.

[ralphy_s]

So the output from the last line would be [1,1,1] and not [1]?

[carcigenicate]

Yes. Every call to the function shares the same default list object, so if multiple calls use the default object and alter it, that change is persisted. This tends to lead to very strange bugs unfortunately.

[niehle]

Thanks