Pollution level using dictionaries

[wavic]

def average(januar):
    k = {}

    # collecting the pollution values for each city
    # the same loop as before
    # I can't write it more clearly
    for day, data in januar.items():
        for city, pollution in data.items():
            if k[city]:                           # if the city is already in the dictionary
                k[city].append(pollution) # just append the pollution
            else:                                  # if it is not
                k[city] = []                     # create the key and put an empty list as a vallue. This list will holds all pollution values for this city
                k[city].append(pollution)  # then append the pollution

The result:

Output:
          k =  {
                  'Athens': [35, 55],
                 'Berlin': [57, 58, 48],
                 'Moscow': [64, 56, 71],
                 'Texas': [126, 53, 34]
                  }

Now you can loop over it and calculate the average easy