Contains/equals

[Karsten Wutzke]

Hello,

I have an object which has a list of other complex objects. How do I
best achieve a complex "contains" comparison based on the object's
class? In Java terms, I'm looking for an equivalent to equals(Object)
in Python. Does a similar thing exist? Directions appreciated.

Karsten

 

[Peter Otten]

I have an object which has a list of other complex objects. How do I
best achieve a complex "contains" comparison based on the object's
class? In Java terms, I'm looking for an equivalent to equals(Object)
in Python. Does a similar thing exist? Directions appreciated.

I can't infer from your question whether you already know about
__contains__(). So there:
.... def __contains__(self, other):
.... return True
....True

 

[Karsten Wutzke]

I can't infer from your question whether you already know about
__contains__(). So there:


...     def __contains__(self, other):
...             return True
...>>> c = Cornucopia()

True

Whoops that easy... Thanks!
Karsten

 

[Alex Hall]

I can't infer from your question whether you already know about
__contains__(). So there:

... def __contains__(self, other):
... return True
...
True

You may also want to use the double equals operator; in Java, one
thing I wish I could do is
String s="abc";
String t="def";
if(s==t)...
In Python, as I understand it, you can define this behavior.

class c(object):
def __init__(self, a=1, b=2):
self.a=a; self.b=b

def __eq__(self, obj):
if self.a==obj.a and self.b==obj.b: return True
return False


You can now say:
obj1=c()
obj2=c()
print(obj1==obj2) #prints True

 

[Steven D'Aprano]

def __eq__(self, obj):
if self.a==obj.a and self.b==obj.b: return True
return False

That would be the same as:

def __eq__(self, obj):
return self.a==obj.a and self.b==obj.b

 

[Tim Chase]

That would be the same as:

def __eq__(self, obj):
return self.a==obj.a and self.b==obj.b

Or, if you have lots of attributes and 2.5+

def __eq__(self, other):
return all(
getattr(self, attr) == getattr(other, attr)
for attr in ['a', 'b', 'c', ...]
)

or even something like

def __eq__(self, other):
return all(
getattr(self, attr) == getattr(other, attr)
for attr in dir(self)
if not attr.startswith("__") and not attr.endswith("__")
)



-tkc

 

[Lawrence D'Oliveiro]

def __eq__(self, obj):
if self.a==obj.a and self.b==obj.b: return True
return False

Is there a “Useless Use Of ...†award category for these “if <boolean> then
return True; else return False†constructs?

 

[Hrvoje Niksic]

Is there a “Useless Use Of ...” award category for these “if <boolean> then
return True; else return False” constructs?

Well, remember that self.a == obj.a can return something other than
bool, and the and operator will evaluate to either False or the last
value. Maybe he doesn't want to propagate the non-bools out of his
__eq__.

what's-next-"useless-use-of-"useless-use-of...""-ly y'rs