Help to find file index based on year, month and week in Python

[DuminduJayasekera]

Hi,

I need to find the file index from a list of rasters that matches year, month and week. My code below work when I give the index manually.  But, I need to loop through many raster files. 

My fmaskrasters list has 180 rasters and as follows:

fmaskrasters = [

Week_1_Sum1981_10_Crawford.tif

Week_1_Sum1982_10_Crawford.tif

.

Week_1_Sum2016_10_Crawford.tif

Week_2_Sum1981_10_Crawford.tif

.

Week_2_Sum2016_10_Crawford.tif

.

Week_5_Sum2016_10_Crawford.tif]

normal raster list has 5 rasters).

normal = [Crawford_Normal_Week_1_1981_2016_10.tif,

Crawford_Normal_Week_2_1981_2016_10.tif,

.

Crawford_Normal_Week_5_1981_2016_10.tif]

Can somebody help me to find the index from each raster list that matches, year, month and week so that I calculate the percent difference. My code below works fine but I need to pass the index that matches year, month and week criteria to find the index of raster from "fmaskrasters" and "normal".

Thanks in advance,

months = [10]
weeks = [1]
years = [1981]

arcpy.env.workspace = r'H:\PRISM_800m_weekly_sum\Crawford\All' 
out = r'H:\PRISM_800m_weekly_sum\Crawford\All\output'

for year in years:
 for month in months:
 for week in weeks:
 arcpy.env.workspace = r'H:\PRISM_800m_weekly_sum\Crawford\All'
 fmaskrasters = arcpy.ListRasters()
 fmaskrasters.sort()
 #"Week_" + str(week) + "_Sum" + str(year) + "_" + str(month) + "_Crawford.tif"
 #for file in fmaskrasters:
 # if fnmatch.fnmatch(file, 'Week_' + str(week) + '_Sum' + str(year) + '_' + str(month) + '_Crawford.tif'):
 # print (file)
 fmaskrasters1=fmaskrasters[0]
 weekras1 = arcpy.Raster(fmaskrasters1) 

 arcpy.env.workspace = r'H:\PRISM_800m_weekly_sum\Crawford\All\output' 
 normal = arcpy.ListRasters()
 normal.sort()
 #normalras = arcpy.Raster(normal["Crawford_Normal_Week_" + str(week) + "_1981_2016_" + str(month) + ".tif"])
 normalras1=normal[0]
 outcalc1 = Minus(normalras1, weekras1) 
 Final = (outcalc1/normalras1)*100

 finras1 = out + "\\" + "Crawford_Normal_Week_" + str(week) + "_Difference" + "_" + str(year) + "_" + str(month) + ".tif"
arcpy.CopyRaster_management(Final,finras1 + "","","","","","")‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍