In Python why does the class
class MyClass():
def __init__(self, _my_dict={}):
self.my_dict = _my_dict
have the following very strange and undesired behaviour:
>>> a = MyClass()
>>> a.my_dict['greet'] ="hallo"
>>> b = MyClass()
>>> b.my_dict['greet'] ="ciao"
>>>
>>> print(a.my_dict)
{'greet': 'ciao'}
>>> print(b.my_dict)
{'greet': 'ciao'}
Note: I know I can fix this by using None as _my_dict default in the __init__ method:
class MyClass():
def __init__(self, _my_dict=None):
if _my_dict is None:
self.my_dict = {}
else:
self.my_dict = _my_dict
So the problem lies clearly with the '{}' as the default for _my_dict: It seems to refer in both instantiations to the same object. But why is this so? And is there a tighter solution than mine with the cumbersome if statement?
