CODEWITHSUNDEEP
python-3.xfor-loopsum
X-cessive Pupil
X-cessive Pupil

Reputation: 68

How to calculate the sum of the output of a for loop

I've built a for loop that goes through the values of a list, enters them as keys for two dictionaries and multiplies the 2 key values together.

When you print, it gives each multiplied value on a new line.

I'd like to add the values together to get a combined total but thus far have not been able to.

#The list and two dictionaries 

List1 = ['coffee', 'tea' , 'cake' , 'scones' ]  

Dictionary1 ={'coffee' :'4', 'tea' :'2' , 'cake' :'6' , 'scones' :'8' }

Dictionary2 = { 'coffee':'25' , 'tea':'18' , 'cake':'45' , 'scones':'30' }


#the for function which runs through the list

for i in range(len(List1)): 
  t = ((int(Dictionary1[List1[i]])*int(Dictionary2[List1[i]]))) 

#now if you print t the following is printed:

100
36
270
240

I'd like to get the sum of these values, but so far I have not been able to.

In order to do so, I've tried sum(t) which produces the error:

">TypeError: 'int' object is not iterable"

I thought that might be a concatenation error so I tried sum(int(t)) but this does not work.

I've also tried turning it into list() " x = list(t) as well as replacing the lines with commas with .replace("\n",",").

All feedback welcome, I think this is probably easily solved but I just haven't been able to get there - thanks.

Upvotes: 2

Views: 2048

Answers (3)

vahdet
vahdet

Reputation: 6729

If I get you right and thinking in the simplest way, you can assign a variable and add up it in every iteration like:

res = 0
for i in range(len(List1)): 
  t = ((int(Dictionary1[List1[i]])*int(Dictionary2[List1[i]])))
  res += t

print(res)

Edit: And as @patrick suggests and discussed in this post, the variable name edited not to be sum

Upvotes: 1

Patrick Artner
Patrick Artner

Reputation: 51623

The error is self explanatory: TypeError: 'int' object is not iterable when executing t. That means t is just a sigular int value. The built in sum() needs an iterable to operate on.

You need to add your int to something for each iteration:

List1 = ['coffee', 'tea' , 'cake' , 'scones' ]  

Dictionary1 ={'coffee' :'4', 'tea' :'2' , 'cake' :'6' , 'scones' :'8' }

Dictionary2 = { 'coffee':'25' , 'tea':'18' , 'cake':'45' , 'scones':'30' }


# accumulate your values into s
s = 0
for i in range(len(List1)): 
  t = ((int(Dictionary1[List1[i]])*int(Dictionary2[List1[i]]))) 
  s += t

print(s) # print sum

Outputs:

646

You can however create a generator comprehension and use the built in sum() function as well:

print (sum ( int(Dictionary1[a])*int(Dictionary2[a]) for a in List1))

Upvotes: 1

rdas
rdas

Reputation: 21275

Here's a list comprehension that does the job

total = sum(int(Dictionary1[x]) * int(Dictionary2[x]) for x in List1)

Output:

646

Upvotes: 1

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