Inconsistency in Python programming language?

[jefsummers]

Easy enough to write -

def is_it_a_duck(str):
    try :
        foo = float(str)
        return True
    except :
        return False

print(is_it_a_duck("4.5"))

This returns true for things that float. OK it catches all exceptions, not just Value, but it works for the task at hand...