New submission from simple_coder878 :
Simple example
from dataclasses import dataclass, field
@dataclass(init=False)
class TestObject(object):
m: str = field(default='hi')
k: list = field(default_factory=list)
def test(self):
print(f'm is {self.m} ')
print(f'k is {self.k}')
if __name__ == '__main__':
myobject = TestObject()
myobject.test()
Produces:
Traceback (most recent call last):
File "H:\unit_test\tests_dataclass.py", line 81, in
myobject.test()
File "H:\unit_test\tests_dataclass.py", line 76, in test
print(f'k is {self.k}')
AttributeError: 'TestObject' object has no attribute 'k'
m is hi
So m is initialized to hi but k just disappears
But wait there's more!
If i do
from dataclasses import dataclass, field
@dataclass(init=False)
class TestObject(object):
m: str = field(default='hi')
k: list = field(default_factory=list)
def test(self):
print(f'm is {self.m} ')
print(f'k is {self.k}')
@dataclass
class InheritedTestObject(TestObject):
def __post_init__(self):
super().__init__()
print(f'Inherited m is {self.m} ')
print(f'Inherited k is {self.k}')
print(f'Inherited g is {self.k}')
if __name__ == '__main__':
myobject = InheritedTestObject()
myobject.test()
It produces:
Inherited m is hi
Inherited k is []
Inherited g is []
m is hi
k is []
Process finished with exit code 0
NO ERRORS!
It seems like a bug to me, but what is the expected behavior in this case? I
would expect the first case to not error out and should have an empty list.
I've only tested this on Python 3.9 so far.
--
components: ctypes
messages: 403182
nosy: simple_coder878
priority: normal
severity: normal
status: open
title: dataclass init=False field with default works but default_factory does
not
type: behavior
versions: Python 3.9
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Python tracker
<https://bugs.python.org/issue45366>
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