Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

Python

Son-Hai Nguyen
Son-Hai Nguyen
2,481 Points

I need help on this ```combiner()``` exercise

Please have a look at my following method. I tested it on Worksplaces, it worked just fine just like the requirement, but somehow the Recheck work kept saying there's a TypeError: sequence item 0: expected str instance, list found Is there anyone know what I missed?

Thank you!!!

instances.py
def combiner(*args):
    numLs = []
    strLs = []
    for a in args:
        if isinstance(a, (int, float)):
            numLs.append(a)
        else:
            strLs.append(a)
    sumInt = str(sum(numLs))
    strLs.append(sumInt)
    return ''.join(strLs)

combiner("apple", 5.2, "dog", 8)          

3 Answers

*args accepts a variable list of arguments (so there can be more than one). The challenge will pass in a single list (any number of items but they will be enclosed in brackets so there will only be one list)

The easiest fix to your code is just remove the * from your parameter

Son-Hai Nguyen
Son-Hai Nguyen
2,481 Points

Great!!! It sounds weird to pass all variables in as a single list anw

The function takes a single argument. If you want to test in a workspace try:

print(combiner(["apple", 5.2, "dog", 8]))
Son-Hai Nguyen
Son-Hai Nguyen
2,481 Points

Thanks Kris, for your answer. But what does it mean? Doesnt the *args stand for a list of arguments? How to iterate through it (since it's still a list right? I saw the [] here) if it's a single argument?

If you add print statements you better see what is going on:

def combiner(*args):
    numLs = []
    strLs = []

    for a in args:
        print(a)

        if isinstance(a, (int, float)):
            numLs.append(a)
        else:
            strLs.append(a)
    sumInt = str(sum(numLs))
    strLs.append(sumInt)

    print(strLs)

    return ''.join(strLs)

print(combiner(["apple", 5.2, "dog", 8]))

In the loop a is a list so since it since it isn't an int or float it is appended to strLs. Since that is the only argument there are no numbers to sum so sumInt = '0'. Append this to strLs you end up with [['apple', 5.2, 'dog', 8], '0']. At which point using join on a list and a string causes the error.