NameError: name 'self' is not defined
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Chapters
00:00 Question
00:22 Accepted answer (Score 201)
00:59 Answer 2 (Score 20)
01:15 Answer 3 (Score 16)
02:05 Thank you
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Full question
https://stackoverflow.com/questions/1802...
Accepted answer links:
[considering late-bound argument defaults]: https://www.python.org/dev/peps/pep-0671/
Answer 3 links:
http://neopythonic.blogspot.com/2008/10/...
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Tags
#python #nameerror
#avk47
ACCEPTED ANSWER
Score 206
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.
ANSWER 2
Score 20
For cases where you also wish to have the option of setting 'b' to None:
def p(self, **kwargs):
b = kwargs.get('b', self.a)
print b
ANSWER 3
Score 17
A self NameError can also occur if you fail to define self inside a method signature. This error typically will appear as TypeError, as there will be a mismatch between expected and given arguments[1]. However, if you accept a variable number of arguments, self will be arg[0], and the variable self will be undefined.
A minimal example.
class Obj:
def foo(*args):
print(self.bar)
>NameError: name 'self' is not defined
Correction:
class Obj:
def baz(self, *args):
print(self.bar)
[1] http://neopythonic.blogspot.com/2008/10/why-explicit-self-has-to-stay.html