CODEWITHSUNDEEP
pythonpython-3.xclasscounter
Luke Poeppel
Luke Poeppel

Reputation: 143

Relevant method to include for collections.Counter

Apologies if this is a repeat on the site (I searched around but couldn't find an answer). Say I have a Person class implemented in Python with name and age parameters, like Person('Bob', 25). Say I then create a list of Person objects and I want to know how many of each instance there are; for example, I might have [Person('Bob', 25), Person('Sally', 40'), Person('Bob', 25), Person('Sarah', 30)]. So there are two instances of Person('Bob', 25) and 1 instance for the remainder; if were to run collections.Counter on this list of objects, it would return this correctly.

My question is: what exactly does collections.Counter look for in a data structure such that the count is correct? I have a more complicated (but hashable) class, and collections.Counter isn't counting the number of elements correctly. I'm sure this is because I just have some method missing from the definition, but I'm not sure what it is.

Upvotes: 0

Views: 40

Answers (1)

aamir
aamir

Reputation: 76

If a == b then hash(a) == hash(b)

You need to implement __hash__() and __eq__()

Upvotes: 1

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