Calculate values between two dicts in Python

Question

I have two dict in python one of quantities and the other of prices the both have the same keys What is the best, and quicks way to calculate Quantity * price for each element in the dict

Example

prices = {'a': '40', 'b': '40', 'c': '35'}
data ={'a': '1', 'b': '2', 'c': '4'}

I want to get a total sum (int) of 260

Answer 1

You can use sum over a generator expression like this:

sum(float(v)*float(prices[k]) for k,v in data.iteritems())

Answer 2

>>> prices = {'a': '40', 'b': '40', 'c': '35'}
>>> data ={'a': '1', 'b': '2', 'c': '4'}
>>> sum(int(prices[x])*int(data[x]) for x in data)
260