Find median or any statistic parameter in loop by array key

import numpy as np


def monthlyMediana(array, length, whichElementIsValue=1, whichElementIsKey=0, startKey=1):
    tmpMonthArray=[[]*length for x in xrange(length)] # how long the array is? (if calculate over months, there are 12 month and then value is 12)
    for liste in array:                               # cycle to reconfiguring array "by key"
        for each in liste:                            # inner cycle to get out values from array
            try:
                tmpMonthArray[each[whichElementIsKey]-startKey].append(each[whichElementIsValue]) #be careful with 'each[0]-startKey' By default the first element = 1, but its index in tmpArray is 0. So to correct it, subtracting helps to get correct index.
            except Exception:
                print ("Check input array in function 'monthlyMediana'! There is no value in defined element '" + str(whichElementIsValue)+"'")
                raise

    i=1
    resultArray=[]
    for each in tmpMonthArray:                      # cycle through reconfigured array to calculate median by key array
        resultArray.append([i,np.median(each)])
        i+=1
    return resultArray



# testing function calculating median from two arrays. the first one-
# array1 is manually created, by hand, consists of pairs - key and value
array1=[[1, 83.08781741696035], [2, 83.00913411194273], [3, 82.87611049475012], [4, 81.9209957077651], [5, 83.29382676081318], [6, 86.43752414116936], [7, 90.28708527096674], [8, 85.4778304673852], [9, 81.50339901314508], [10, 82.86330480401524], [11, 81.2255531150904], [12, 81.61939222634093]]
i=1

# the second array2 is synthetically generated in next loop and it will consist half the values of array1, keeping the same keys
array2=[]
for each in array1:
    tmp=[i,each[1]/2]
    array2.append(tmp)
    i+=1

#lets check them
print "array 1", array1
print ""
print "array 2", array2
print""
#now we need to combine both arrays into array, which can be given to monthlyMediana function.
# it is like a wrapeer, wraps both small arrays.
wrapperArray=[]
wrapperArray.append(array1)
wrapperArray.append(array2)

#check out the configuration of such wrapper array. simple, huh?
print "wrapper array", wrapperArray
print""


length=len(array1) #how many keys we have?
print "how many keys we have?", length
print ""

print "calculated medianas by key", monthlyMediana(wrapperArray,length,1,0,1)
print""
print "calculated medianas by key with default whichElementIsValue=1, whichElementIsKey=0, startKey=1", monthlyMediana(wrapperArray,length)