FacesOfMu FacesOfMu - 8 days ago 6
Python Question

Python Count Elements in a List of Objects with Matching Attributes

I am trying to find a simple and fast way of counting the number of Objects in a list that match a criteria.
e.g.

class Person:
def __init__(self, Name, Age, Gender):
self.Name = Name
self.Age = Age
self.Gender = Gender

# List of People
PeopleList = [Person("Joan", 15, "F"),
Person("Henry", 18, "M"),
Person("Marg", 21, "F")]


Now what's the simplest function for counting the number of objects in this list that match an argument based on their attributes?
E.g., returning 2 for Person.Gender == "F" or Person.Age < 20.

Answer
class Person:
    def __init__(self, Name, Age, Gender):
        self.Name = Name
        self.Age = Age
        self.Gender = Gender


>>> PeopleList = [Person("Joan", 15, "F"), 
              Person("Henry", 18, "M"), 
              Person("Marg", 21, "F")]
>>> sum(p.Gender == "F" for p in PeopleList)
2
>>> sum(p.Age < 20 for p in PeopleList)
2
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