Say you have a list of people.
class Person:
def __init___(self, name, id):
self.name = name
self.id = id
people = []
for x in xrange(0,100)
#find people and append to people list
Now, I have a list of people objects. How could I most efficiently find, say, a person whose name is "Bob" from the people list?
With just a list and no other indices, you have to use a list comprehension:
matching = [p for p in people if p.name == 'Bob']
but if you have to do that a lot, you may want to create an index:
from collections import defaultdict
nameindex = defaultdict(list)
for person in people:
nameindex[person.name.lower()] = person
nameindex['bob'] # a list of people named Bob.
This way you only have to loop through all your people once (cost O(N)), after which any name lookup has constant cost (O(1)).
For this exact scenario, you'll want to use a dictionary:
from collections import defaultdict
people = [...]
name_to_people = defaultdict(list)
for p in people:
name_to_people[p.name].append(p)
Then whenever you want to find all people whose name is "Bob":
bobs = name_to_people["Bob"]
It will return empty list for no match, a list with one element if there's exactly one person with that name, or a list with multiple elements if there are multiple Bobs.
lambda there; use list (the type constructor) instead.One way you could do it is by building a class to hold collections of people objects. One of the best ways to do this may be something like the following code:
class People:
def __init__(self):
self.members = {}
def add_person(self, person):
self.members[person.name] = person
def __getitem__(self, name):
return self.members[name]
class Person:
def __init__(self, name, id):
self.name = name
self.id = id
Now you should be able to fill up the People object like such:
# Add people to a People object
people = People()
people.add_person(Person('Bob', 1))
people.add_person(Person('Surly', 2))
# Get a person by their name
people['Bob'] # Returns instance that is People('Bob', 1)
Also just to let you know, I think your Person class' __init__ method has too many underscores in it. Hope this helps.
names andids to specific people. That would be the fastest approach, I think.