Question

Apologies if this question has already been asked but I do not think I know the correct terminology to search for an appropriate solution through google.

I would like to select an object from a list of objects by the value of it’s attribute, for example:

class Example():
    def __init__(self):
        self.pList = []
    def addPerson(self,name,number):
        self.pList.append(Person(self,name,number))

class Person():
    def __init__(self,name,number):
        self.nom = name
        self.num = number


a = Example()
a.addPerson('dave',123)
a.addPerson('mike',345)

a.pList #.... somehow select dave by giving the value 123

in my case the number will always be unique

Thanks for the help

Answer 1

One option is to use the next() built-in:

dave = next(person for person in a.pList if person.num == 123)

This will throw StopIteration if nothing is found. You can use the two-argument form of next() to provide a default value for that case:

dave = next(
    (person for person in a.pList if person.num == 123),
    None,
)

A slightly more verbose alternative is a for loop:

for person in a.pList:
    if person.num == 123:
        break
else:
    print "Not found."
    person = None
dave = person