On Sunday, December 8, 2013 10:32:31 AM UTC-8, rafae...@gmail.com wrote:
[snip]
> def people(age):
> people=lambda age: [name for name in dic if dic[name]==age]
>
> people(20)
[snip]
> this is the code i have so far(with the help of the first post ;p). i
> understand how a function and a dictionary works and what I'm asked to find.
> but i don't get the lambda age part.
Well then, don't use it! It's clear that you are new, and at least you have
posted some code now, so let me try to help.
>and this code doesn't give me any result
Right, for TWO reasons.
First problem: if your function does not end with a statement like "return
people", the function returns a special Python object called None.
Now, if it were me, I would not "wrap" the calculation of your "people" list
inside a "people" function for such a short program. But this is apparently a
requirement of your assignment. My guess is, in the future, you will write a
program that calls the people function multiple times.
The "lambda" word has to do with creating something called an "anonymous
one-line function." You don't need that here. It's more advanced Python.
What you want to do is compute and, importantly, return a list calculated from
your dictionary. That is accomplished by this expression:
"[name for name in dic if dic[name]==age]"
This is called a "list comprehension." Do you understand what this does? It's
fairly advanced. I don't teach list comprehensions to my Python students for
the first several lessons.
So, now that you have created the list, let's make sure that Python doesn't
lose it. Let's assign a NAME to it. By the way, it's probably not good form
to use the same name for a function and any of its internal variables. Pick a
different name for your list: for example, "p". Then, return p from your
function to your main program. My suggested rewrite of your function would be:
"""
def people(age):
p = [name for name in dic if dic[name]==age]
return p
"""
The truth is that you can cut this down by even one more line. This function
doesn't need to hold on to the result after it is done returning it, but the
computation of the result can be accomplished in one line. Therefore this will
also work:
"""
def people(age):
return [name for name in dic if dic[name]==age]
"""
OK, that takes care of Problem 1.
Second problem: you call the "people" function with your statement
"people(20)", but you don't do anything with the output. Once you fix the
people function by providing a proper return statement, what does the main
program do with the output of the function? Right now, it just throws it away.
One solution to the problem is to make sure that the function's output gets a
name. Try:
"""
result = people(20)
"""
Now, what do you want to do with result? I will wait to see your answer on
that one before I intervene again.
--
https://mail.python.org/mailman/listinfo/python-list
