How to iterate over two dictionaries at once and get a result using values and keys from both

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def GetSale():#calculates expected sale value and returns info on the stock with              highest expected sale value
      global Prices
      global Exposure
      global cprice
      global bprice
      global risk
      global shares
      global current_highest_sale
      best_stock=' '
      for value in Prices.values():
          cprice=value[1]
          bprice=value[0]
          for keys, values in Exposure.items():
             risk=values[0]
             shares=values[1]
             Expected_sale_value=( (cprice - bprice ) - risk * cprice) * shares
             print (Expected_sale_value)
             if current_highest_sale < Expected_sale_value:
                current_highest_sale=Expected_sale_value
                best_stock=Exposure[keys]
     return best_stock +" has the highest expected sale value"

Above is my code currently. For some reason though, it appears to be doing the first loop, then the second, then the second, then the first, then the second. It appears to do the second loop each time it gets to it before going back to the first for loop. It is because of this that the answers I'm getting are not correct.

python loops
3 Answers

The question isn't well defined, and the answer accepted will fail for some dictionaries. It relies on key ordering, which isn't guaranteed. Adding additional keys to a dictionary, removing keys, or even the order they are added can affect the ordering.

A safer solution is to choose one dictionary, d in this case, to get the keys from, then use those to access the second dictionary:

d = {'a':5, 'b':6, 'c': 3}
d2 = {'a':6, 'b':7, 'c': 3}
[(k, d2[k], v) for k, v in d.items()]

Result:

[('b', 7, 6), ('a', 6, 5), ('c', 3, 3)]

This isn't more complex than the other answers, and is explicit about which keys are being accessed. If the dictionaries have different key orderings, say d2 = {'x': 3, 'b':7, 'c': 3, 'a':9}, consistent results are still given.

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