In python, is there some kind of mapping to return the "False value" of a type?

Question

I am looking for some kind of a mapping function f() that does something similar to this:

f(str) = ''
f(complex) = 0j
f(list) = []

Meaning that it returns an object of type that evaluates to False when cast to bool.

Does such a function exist?

question from:https://stackoverflow.com/questions/49294222/in-python-is-there-some-kind-of-mapping-to-return-the-false-value-of-a-type

Answer 1

No, there is no such mapping. Not every type of object has a falsy value, and others have more than one. Since the truth value of a class can be customized with the __bool__ method, a class could theoretically have an infinite number of (different) falsy instances.

That said, most builtin types return their falsy value when their constructor is called without arguments:

>>> str()
''
>>> complex()
0j
>>> list()
[]