Hello, need assistance with this question

Hi Lindsay,

Your first issue is with your use of the isinstance built-in function. Let's revisit the documentation for this function to ensure we're on the same page:

isinstance(object, classinfo)
Return true if the object argument is an instance of the classinfo argument, or of a (direct, indirect or virtual) subclass thereof...

We want to pass isinstance a value of some type, and then compare it to a value of a known type (or to the known type itself) so that we can behave differently for values of ints and strings.

As the challenge tells us, our function input is a list, whose elements are some combination of numbers (possibly ints, possibly floats) and strings:

...takes a single argument, which will be a list made up of strings and numbers.

A list is neither an int nor a string. Therefore any comparison to either int or string will evaluate to False, as illustrated here:

>>> l = [1, 'hello']
>>> isinstance(l, int)
False
>>> isinstance(l, str)
False
>>> isinstance(l, list)
True

To proceed with this question, consider approaching this using the most simple concepts possible:

• you know you are getting a list as an input;
• you can use a for loop to iterate through a list;
• you can check the type of each element in the list (instead of checking the type of the list itself);
• you can assign values to variables (you might consider keeping a strings variable: a list of all the strings you've seen so far; and a number variable: the running total of the numbers so far;
• you can use join() to combine the strings in the strings variable;
• you can use str() to convert a number to a string;
• you can use + to concatenate two strings.

If you've made it to object oriented Python, all of the above concepts should be familiar to you. If any are not, let me know and I'll give you some pointers.

As for your specific questions:

1. How to add multiple arguments in the function call

I'm not sure exactly what you are asking here, you want to add values while calling a function? If so, you can do it like this:

>>> my_function(3 + 5)    # this is equivalent to calling my_function(8)

Remember though, you will not call your function. You just write the function. Treehouse will call your function in the background with (probably multiple) secret values. As such, you need to write your function in such a way that it can work with any valid input (a valid input, in this case, being defined in the question as "a list made up of strings and numbers").

1. How to add the integer items together

First, remember that you are not necessarily just going to get integers. The question specifically states "numbers" not integers, and then shows you an example that includes both integers and floats:

For example, with the input ["apple", 5.2, "dog", 8], combiner would return "appledog13.2"

Python can handle adding floats and integers without needing you to manually typecast the values. It will treat any sum of ints and floats as a float: For example:

>>> total = 1 + 1
>>> type(total)    # an int plus an int is an int
<class 'int'>
>>> total = 1 + 3.14
>>> type(total)   # an int plus a float is a float
<class 'float'>
>>> total = 2.72 + 1
>>> type(total)   # a float plus an int is a float
<class 'float'>

Hope this points you in the right direction.

Cheers

Alex

Thanks, Alex, your response has a lot of great gems. I'm going to review and work through the question again. Thanks!

@AlexKoumparos

Okay, the below works, but it is clunky. Any thoughts on how to condense?

strings=[]
numbers=[]
combined=[]

def combiner(item):

    for value in item:
        if isinstance(value,int):
            numbers.append(value) 
        if isinstance(value,float):
            numbers.append(value)
        if isinstance(value,str):
            strings.append(value)        


    new = ''.join(strings)
    combined.append(new)

    total = sum(numbers)
    combined.append(str(total))
    final = ''.join(combined)

    print(final)


combiner([1,"hello",2, 4.5,"dog"])