optimization problem

[jenya56]

My program runs but it is soooooooooo slow. I have lots of data files I am reading and this for loop is where the program takes FOREVER.......N ote I declare data_ncdc=[] and ncdc_station=[]. Any suggestions would be appreciated.... . THANKS!!!!!

for il in range(len(data_ncdc)):
   coord_ind = common_index(ave_lon_ncdc,ave_lat_ncdc, data_ncdc[il][0],  data_ncdc[il][1])
     if coord_ind == None:
        ave_lon_ncdc.append(float(data_ncdc[il][0]))
        ave_lat_ncdc.append(float(data_ncdc[il][1]))
        ncdc_station.append(float(data_ncdc[il][3]))
     else:
        ncdc_station[coord_ind[0]].extend(float(data_ncdc[il][3]))

def common_index(list1, list2, val1, val2):
   assert len(list1) == len(list2), "List not of equal length"
   for i in range(len(list1)):
     if list1[i] == val1 and list2[i] == val2:
        return [i]

[Glenton]

Perhaps if you told us what you were trying to do?!

A good way to improve speed dramatically is to work with numpy arrays and array operations rather than loops.

Eg if a is a large list of numbers

a=array(a)
b=a*2+10

would be much quicker than

b=[]
for i in a:
    b.append(2*i+10)

This is because all the heavy lifting is done in C/C++