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Python Python Collections (Retired) Dungeon Game Random Choices

Posted by Tony Kirkland
Tony Kirkland
2,400 Points

Unsure why I am getting 'try again'

In Python Collections I have the following task:

Create a function named nchoices() that takes an iterable and an integer. The function should return a list of n random items from the iterable where n is the integer. Duplicates are allowed.

My code:

def nchoices(choice_count, my_iter):
    random_list = []
    while choice_count > 0:
        random_list.append(random.choice(my_iter))
        choice_count -= 1
    return random_list

My test (using Pycharm) was to call nchoices as follows:

grid = list(range(30)) print(nchoices(5, grid))

Results appears to be within the expected set:

[6, 24, 0, 7, 20] [20, 26, 1, 19, 25] etc.

Am I misreading the question? I get no errors with executing the code but it doesn't pass the check work validation.

Thanks in advance for your help!

4 Answers

Haider Ali
.a{fill-rule:evenodd;}techdegree seal-36
Haider Ali
Python Development Techdegree Graduate 24,728 Points

Hi Tony, there are just a couple of things wrong with your code. Firstly, the order of the arguments passed in should be the iterable then the number. Secondly, you forgot to import random. Also, the challenge asks you to pick something out of the iterable for each number in range(the_number_you_passed_in). This can be done with the following code:

import random

def nchoices(my_iter, choice_count): #you should have passed arguments in this way round
    random_list = []
    for i in range(choice_count):
        random_list.append(random.choice(my_iter))

    return random_list

If you have any further questions, please feel free to leave a comment. :)

Thanks,

Haider

Tony Kirkland
Tony Kirkland
2,400 Points

Is the reasoning behind the ordering of the parameters to the function as simple as how it was worded in the challenge? Functionally the order passed shouldn't matter as long as the function uses the values passed correctly. Correct?

As for the import I got that a bit later.. Seem a bit ambiguous in wording though as the challenge just says 'create the function' and normally one wouldn't import within the function creation. Explains why it was working in Pycharm though as I was importing there.

Haider Ali
.a{fill-rule:evenodd;}techdegree seal-36
Haider Ali
Python Development Techdegree Graduate 24,728 Points

Hi Tony, I understand where you are coming from, I will show you how the order of passing in parameters can affect your code. For example, if I had the following function:

def example(a_string, a_number):
    for i in range(a_number):
        print(a_string)

This would print the string out as many times as a_number. E.g. if i called the following code, this is what would happen:

example('hello', 3)

->hello
->hello
->hello

However, if I ran this:

example(3, 'hello')

I would get a TypeError saying that an str object cannot be interpreted as an integer. This is because functions use parameters in the order you pass them in so it would use 3 as the string and 'hello' as the number. This can be a little confusing at first but having a little play around in the python shell should clear things up for you :).

Tony Kirkland
Tony Kirkland
2,400 Points

I understand. As long as the order that the parameters are passed in the function call match the order that the that the function is expecting them in then it is correct. One must be sure that the orders match tho or as you stated there will be errors (or worse unexpected results) in the code.

Urs Merkel
PLUS
Urs Merkel
Courses Plus Student 4,552 Points
Urs Merkel
Urs Merkel
Courses Plus Student 4,552 Points

Hi guys, could someone please explain me, why you are using 'while' and decrease it within your for loop. Shouldn't the for loop already do its job?

Haider Ali – you are decreasing the variable in your for loop, you use as an for-loop-argument, why is that so? Shouldn't it be working with just the for-loop?

Thanks for your help

Haider Ali
.a{fill-rule:evenodd;}techdegree seal-36
Haider Ali
Python Development Techdegree Graduate 24,728 Points

Hi there Urs, thank you for pointing that out. The answer to your question is yes, the loop will run just fine without the decreasing the counter. Now that I look at my code, I have no idea why I have put that there, I must have thought I was using a while loop for some reason. Thats what I get for rushing my answers! :)

Urs Merkel
PLUS
Urs Merkel
Courses Plus Student 4,552 Points
Urs Merkel
Urs Merkel
Courses Plus Student 4,552 Points

Thanks Haider for your quick reply and pointing it out, I was just confused :D and unsure what the deeper meaning of this could be.

Gianmarco Mazzoran
Gianmarco Mazzoran
22,076 Points
Gianmarco Mazzoran
Gianmarco Mazzoran
22,076 Points

Hi,

I think it's because you need a for loop in order to randomly appends items to the random_list.

Here's my code (that's ok for the challenge):

task.py 
import random


def nchoices(iterable, integer):
    rand_list = []
    for item in iterable:
        while integer > 0:
          rand_list.append(random.choice(item))
          integer -= 1
    return rand_list