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Python Functional Python The Lambda Lambada Reduce

James N
James N
17,864 Points
Posted by James N
James N
17,864 Points

Think i have it, but don't know what to do with reduce()

I've been working on this code challenge for some time now, but i'm stuck!

Here's my error (what i get when i run it in a general workspace):

error.txt 
Traceback (most recent call last):           
  File "Untitled.py", line 17, in <module>   
    print(list(total))                       
  File "Untitled.py", line 13, in product_sales                                           
    return twomemtup[0] * twomemtup[1]       
TypeError: 'float' object is not subscriptable

Here's my code:

prices.py 
from operator import add
from functools import reduce

prices = [
    (6.99, 5),
    (2.94, 15),
    (156.99, 2),
    (99.99, 4),
    (1.82, 102)
]

def product_sales(twomemtup):
  return twomemtup[0] * twomemtup[1]

total = map(product_sales, reduce(add, prices))

(in the variation on the workspace, i add:)

print(list(total))

Thanks for your help in advance.

PS: the treehouse code challenge engine says:

 Bummer! total isn't the right amount.

3 Answers

Steven Parker
Steven Parker
231,268 Points
Steven Parker
Steven Parker
231,268 Points

You nearly had it. You just need to map first, and then reduce:

total = reduce(add, map(product_sales, prices))
Seth Kroger
Seth Kroger
56,413 Points
Seth Kroger
Seth Kroger
56,413 Points

You have map and reduce reversed. Since reduce reduces a collection into a single value, and you are trying to find a sales total from individual sales, it should be the outermost function.

total = reduce(add, map(product_sales, prices))
James N
James N
17,864 Points
James N
James N
17,864 Points

Thanks! since both of you responded on the same day, i don't know who to give best answer!

I though i was doing it first!

man, i'm dumb!