Understanding and using dict
Your function after_task, as it is currently written, returns a dict (for "dictionary"). This is a standard python class which associates keys and values. You can iterate over a dict using .keys(), .values() or .items():
d = {'a': 'Alice'; 'b': 'Bob'; 'c': 'Chong'}
for k in d.keys():
print(k)
for v in d.values():
print(v)
for k,v in d.items():
print('{}: {}'.format(k, v))
Fixing your code
If I understand your question correctly, your problem is that your function is returning a dict, but you want to return simply the list of values in the dict, rather than associations key:value.
You can do that with d.values():
def after_tasks(visits):
d = {task: {name for name, ta in visits if ta == task} for name, task in visits}
return list(d.values())
print(after_tasks([("Ana", "coffe"), ("Berta", "coffe"), ("Cilka", "exercise"), ("Dani", "doctor")]))
# [{'Ana', 'Berta'}, {'Cilka'}, {'Dani'}]
Completely different code for the same problem
This is another suggestion using itertools.groupby.
import itertools
import operator
def after_tasks(visits):
return [[name for task,name in g] for k,g in itertools.groupby(sorted([(k,v) for v,k in visits]), key=operator.itemgetter(0))]
print(after_tasks([("Ana", "coffe"), ("Berta", "coffe"), ("Cilka", "exercise"), ("Dani", "doctor")]))
# [['Ana', 'Berta'], ['Dani'], ['Cilka']]
Relevant documentation
