How to add a set of multiple values to a key? - python-3.x

Question

I created a class which is basically a hobby book. The book can be accessed by two methods, enter(n,h) which takes a name and keep adding hobbies to that name(one name can have multiple hobbies). The other method returns a set of hobbies for a particular name. My hobby book is storing every hobby that I insert to one name. Can someone help me fixing it?
class Hobby:
def __init__(self):
self.dic={}
self.hby=set()
def enter(self,n,h):
if n not in self.dic.items():
self.dic[n]=self.hby
for k in self.dic.items():
self.hby.add(h)
def lookup(self,n):
return self.dic[n]
I tried running following cases
d = Hobby(); d.enter('Roj', 'soccer'); d.lookup('Roj')
{'soccer'}
d.enter('Max', 'reading'); d.lookup('Max')
{'reading', 'soccer'} #should return just reading
d.enter('Roj', 'music'); d.lookup('Roj')
{'reading', 'soccer','music'} #should return soccer and music

Answer 1

Why are you re-inventing a dict here? Why are you using a separate set to which you always add values, and reference it to every key which ensures that it always returns the same set on a lookup?
Don't reinvent the wheel, use collections.defaultdict:
import collections
d = collections.defaultdict(set)
d["Roj"].add("soccer")
d["Roj"]
# {'soccer'}
d["Max"].add("reading")
d["Max"]
# {'reading'}
d["Roj"].add("music")
d["Roj"]
# {'soccer', 'music'}
.
UPDATE - If you really want to do it through your own class (and before you do, watch Stop Writing Classes!), you can do it as:
class Hobby(object):
def __init__(self):
self.container = {}
def enter(self, n, h):
if n not in self.container:
self.container[n] = {h}
else:
self.container[n].add(h)
def lookup(self, n):
return self.container.get(n, None)
d = Hobby()
d.enter("Roj", "soccer")
d.lookup("Roj")
# {'soccer'}
d.enter("Max", "reading")
d.lookup("Max")
# {'reading'}
d.enter("Roj", "music")
d.lookup("Roj")
# {'soccer', 'music'}
Note how no extra set is used here - every dict key gets its own set to populate.