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Python Python Collections (2016, retired 2019) Tuples Packing

Posted by Kamen Mackay
Kamen Mackay
2,179 Points

Help with understanding tuples/variable assignments?

So my solution worked but, as I was working on this problem,I don't understand why 'foo' is not being unpacked and multiplied. Here is my function:

def multiply(*args):
    product = 1
    for arg in args:
        product = arg * product
    return product

First example:

foo = ( 1,2,3,4 )
multiply(foo)

multiply returns '(1,2,3,4)

Second example:

But if I feed the numbers directly into the function rather than using 'foo':

multiply(1,2,3,4)

multiply returns '24'

Can someone explain what's happening and what I'm doing wrong?

Alexander Davison
Alexander Davison
65,469 Points

Please format your code properly so that people can read it. Refer to the Markdown Cheatsheet below the answer box :arrow_down:

It says:

Wrap your code with 3 backticks (```) on the line before and after. If you specify the language after the first set of backticks, that'll help us with syntax highlighting.

print("Hello world")

1 Answer

Viraj Deshaval
Viraj Deshaval
4,874 Points
Viraj Deshaval
Viraj Deshaval
4,874 Points

Your code is correct. The only thing where you are doing mistake is calling a function with tuple. You call your function as multiply(5, 6, 8). Try this it will work.

Kamen Mackay
Kamen Mackay
2,179 Points

I understand that but my question was how would I pass it as a variable and have it return the same result? I know that I passed this section but I'd like to understand some of the finer details so I can master Python.

Alexander Davison
Alexander Davison
65,469 Points

Try:

def multiply(args):
    product = 1
    for arg in args:
        product = arg * product
    return product

(Note that there's no asterisk before the args parameter)

Viraj Deshaval
Viraj Deshaval
4,874 Points
Viraj Deshaval
Viraj Deshaval
4,874 Points

Good question. Let me explain you what happened to the code you developed and why it didn't worked.

So when you execute your code i.e.

def multiply(*args):  # args: <type 'tuple'>: ((1, 2, 3, 4), )
    product = 1   # product: <type 'tuple'>: (1, 2, 3, 4)
    for arg in args:   #  arg: <type 'tuple'>: (1, 2, 3, 4)
        product = arg * product
    return product

foo = (1,2,3,4)
print(multiply(foo))

what this does is you have a tuple named foo and whole tuple(((1, 2, 3, 4), ) got passed. Why? because if you see the functionality of tuple i.e. it will unpacks the values to the variables available in left side, but in your case only single variable so whole tuple (1,2,3,4) is equal to foo. so now if we loop through this the program will return the product = (1,2,3,4) instead of 24.

To resolve this what you need to now think is how you can pass the values as multiply(1, 2, 3, 4) instead of multiply((1, 2, 3, 4), ). Let's solve now your query. In order to pass the values from tuple variable follow below steps: Step - 1 : First of all you need to pack the tuple variable i.e multiply(*foo) Step - 2: Then you pass the packed tuple to function and then function will loop through each values inside tuple. See below what I mean.

def multiply(*args):    #args: <type 'tuple'>: (1, 2, 3, 4)
    product = 1    #product: 24
    for arg in args:
        product = arg * product
    return product

foo = (1,2,3,4)
print(multiply(*foo))

In this way you can pack and unpacks the tuple.

HappyCoding