Calculate monthly average from list

 #This function creates a monthly average from list with
 #such structure (["%Y-%m-%d %H:%M:%S", float],["%Y-%m-%d %H:%M:%S", float]..)

def monthlyAverage(array):
    tmpMonthArray=[[]*12 for x in xrange(12)]
    resultArray=[]
    for eachPair in array:
        #print eachPair[0]
        dateObjekts=datetime.datetime.strptime(eachPair[0],"%Y-%m-%d %H:%M:%S")
        menesis=dateObjekts.month
        tmpMonthArray[menesis-1].append(eachPair[1])
    i=1
    for each in tmpMonthArray:
        resultArray.append([i,sum(each)/len(each)])
        i+=1
    print resultArray