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I have two lists and I would like to find a way to select them based on names.

In list one I have a series of tif files:

list1=['LT50300281984137PAC00_sr_band1.tif',
,'LT50300281984137PAC00_sr_band2.tif'  
'LT50300281984137PAC00_sr_band3.tif','LT50300281994260XXX03_sr_band1.tif',
'LT50300281994260XXX03_sr_band2.tif',
'LT50300281994260XXX03_sr_band3.tif']

in list two I have two files:

list2=[LT50300281984137PAC00_mask.tif,LT50300281994260XXX03_mask.tif]

I want to exectue a process (which I won't ask how to do here) for files in list one which start with LT50300281984137PAC00 to the file in list 2 which starts the same way, and the same for the files which start with LT50300281994260XXX03.

I think it will go something like:

#select the files based on names
for i in list1:
    if i[0:20] in list2:
#this code executes the process I want ONLY if the naming matches
        for b in list1:
            arcpy.gp.ExtractByMask_sa(b,list2,outraster)
     else:
          print('Done')

So basically if the file names in list 1 match those in list 2 I want to execute my process otherwise print done

Edit:

New code being tried is:

import arcpy

arcpy.env.workspace=r'F:\Sheyenne\Atmospherically Corrected Landsat\hank_practice'

list1 = arcpy.ListRasters("*band*")

list2 = arcpy.ListRasters("*_nocloud.tif")  

for raster in list1:
  rasterName = raster
  rasterMask = "" #initialize your variable to be populated in the inner loop
  for mask in list2:
    if mask.startswith(rasterName):
      rasterMask = mask
      break #break out of the inner loop - we have a match
  if rasterMask != "": #just to make sure we have something
    #generic naming
    outraster = rasterName.replace(".tif", "_masked.tif")
    arcpy.gp.ExtractByMask_sa(rasterName,rasterMask,outraster)
  • Have you thought about using python's startwith() in a loop? Like if blah.startswith(anotherstring) add to a sub list to be processed. Info: tutorialspoint.com/python/string_startswith.htm – Branco Aug 11 '15 at 16:18
  • I have not, but it looks like exactly what I want to do! – spotter Aug 11 '15 at 16:19
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I thought about this and you might have luck with a loop over your primarily list and an inner loop looking for its mask.

How about trying something like this:

for raster in list1:
  rasterName = raster
  rasterMask = "" #initialize your variable to be populated in the inner loop
  for mask in list2:
    if mask.startswith(rasterName.split("_")[0]):
      rasterMask = mask
      break #break out of the inner loop - we have a match
  if rasterMask != "": #just to make sure we have something
    #generic naming
    outraster = rasterName.replace(".tif", "_masked.tif")
    arcpy.gp.ExtractByMask_sa(rasterName,rasterMask,outraster)

Edit... I thought on the outraster part, you can just replace part of the input's name. Typically, I take the extension and replace it with "_somethingToKnowItIsAProduct" and add the extension back in. So, the .replace(".tif", "_masked.tif) would mark your output like LT50300281984137PAC00_sr_band1_masked.tif.

  • one question, where should outraster be placed? I put it after rasterMask=mask but it didn't seem to work – spotter Aug 11 '15 at 16:32
  • @spotter see the edit. – Branco Aug 11 '15 at 16:36
  • thats how I do it as well, the code runs with no errors, but nothing executes either. I think this is close to where I want to be though so I will keep chipping away at it. Thank you! – spotter Aug 11 '15 at 16:39
  • Where are you running the program? You can add messages in to see what may or may not be happening. I am assuming you're running ArcMap 9.3 so the arcpy call should be right. – Branco Aug 11 '15 at 16:51
  • I am using ArcMap 10.3 but I actually run arcpy out of the Anaconda environment. when I print things out it appears that rasterMask is not populated in the code. I added an edit so you can see exactly what I am running my code as now. – spotter Aug 11 '15 at 16:54
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Comparing string is pretty straight forward in python. You can take a look at: https://stackoverflow.com/questions/2988017/string-comparison-in-python-is-vs

an easy way to get a list of filenames is the listdir command.

If you only want to compare part of strings you can use a wildcard * or the startswith function http://www.tutorialspoint.com/python/string_startswith.htm

some example code:

import os

pathname1 = "path1"
pathname2 = "path2"
uniquecharacters   = 5  # defines how many characters at the end of the string are unique. 

matches = 0 
for item1 in os.listdir(pathname1):    
    for item2 in os.listdir(pathname2):
        print item1 
        print item2
        if item1.startswith(item2[:-uniquecharacters]):
            print "we have a match"
            matches = matches + 1 

print "we have %s match(es)" %( matches )    

hope this helps

0

Branco's answer was so helpful! However, in my case, I changed the code a little bit especially in startswith part because only the middle part of the raster name and mask name would match. I hope I could contribute something to stackexchange!

for mask in masklist:
    if mask.startswith(rasterName.split("_")[3], 17, 26) == True:
        rasterMask = mask
        break

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