Why does this code fail if there is no cls. before __TEXT
__TEXT = "abcde"
print(__TEXT)
class aaa():
@classmethod
def bbb(cls):
print(__TEXT)
aaa.bbb()
The output is:
abcde
Traceback (most recent call last):
File "<string>", line 9, in <module>
File "<string>", line 7, in bbb
NameError: name '_aaa__TEXT' is not defined
If you make __TEXT a class variable and try to reference it without the class prefix as follows:
class aaa():
__TEXT = "abcde"
@classmethod
def bbb(cls):
print(cls.__TEXT)
print(__TEXT)
x = aaa()
x.bbb()
You get the same error but it doesn't make sense:
abcde
Traceback (most recent call last):
File "<string>", line 10, in <module>
File "<string>", line 7, in bbb
NameError: name '_aaa__TEXT' is not defined
In PEP 8, they specifically say:
__double_leading_underscore: when naming a class attribute, invokes name mangling (inside class FooBar, __boo becomes _FooBar__boo ...).
Notice the selection in bold. In the exact same sentence where they draw attention to mangling's use in naming class attributes, they state that the mangling happens to any __boo inside of the class, which perfectly explains what you are observing.
Not quite sure if that was the error, but you can just make the function require a parameter text, that seems to work just fine. You need to give me more information though so I can try to help.
__TEXT = "abcde"
print(__TEXT)
class aaa():
@classmethod
def bbb(self, __TEXT):
print(__TEXT)
aaa.bbb(__TEXT)
A double underscore prefix causes the Python interpreter to rewrite the attribute name in order to avoid naming conflicts in subclasses.
This is also called "name mangling." The interpreter changes the name of the variable in a way that makes it harder to create collisions when the class is extended later.
Reference docs: https://docs.python.org/3/tutorial/classes.html#private-variables