["python","nameerror"]
NameError: name 'self' is not defined

Why such structure class A: def __init__(self, a): self.a = a def p(self, b=self.a): print b gives an error NameError: name 'self' is not defined?
Default argument values are evaluated at function define-time, but self is an argument only available at function call time. Thus arguments in the argument list cannot refer each other. It's a common pattern to default an argument to None and add a test for that in code: def p(self, b=None): if b is None: b = self.a print b Update 2022: Python developers are now considering late-bound argument defaults for future Python versions.