Question

I’m trying to write a Python code that will import LANDSAT satellite images into Grass GIS by adapting this code: http://grass.osgeo.org/wiki/LANDSAT

LANDSAT tiles are downloaded as folders, each containing 7 tiff images (Band 1-7). I therefore have a directory which contains several subdirectories (one for each LANDSAT tile).

My code at present is as follows:

#!/usr/bin/python

import os
import sys
import glob
import grass.script as grass

def import_tifs(dirpath):

    for dirpath, dirname, filenames in os.walk(dirpath):
        for dirname in dirpath:

        dirname = os.path.join(dirpath,dirname)

            for file in os.listdir(dirname):
                if os.path.splitext(file)[-1] != '.TIF':
                    continue
                ffile = os.path.join(dirname, file)
                name = os.path.splitext(file)[0].split(dirname)[-1]

                grass.message('Importing %s -> %s@%s...' % (file, name, dirpath))

                grass.run_command('r.in.gdal',
                                  flags = 'o',
                                  input = ffile,
                                  output = name,
                                  quiet = True,
                                  overwrite = True)

def main():                                 
    if len(sys.argv) == 1:
        for directory in filter(os.path.isdir, os.listdir(os.getcwd())):
            import_tifs(directory)
    else:
        import_tifs(sys.argv[1])

if __name__ == "__main__":
    main()

I’m getting the following error:

Traceback (most recent call last):
  File "C:/Users/Simon/Documents/import_landsat2.py", line
40, in <module>
    main()
  File "C:/Users/Simon/Documents/import_landsat2.py", line
37, in main
    import_tifs(sys.argv[1])
  File "C:/Users/Simon/Documents/import_landsat2.py", line
17, in import_tifs
    for file in os.listdir(dirname):
WindowsError: [Error 3] The system cannot find the path
specified: 'dirpath\\C/*.*'

Can anyone explain what is happening and what I need to do to fix it, or suggest an alternative? Thanks.

Answer 1

I believe your main problem is that dirname in os.walk() returns a list (not a string), so your subsequent strings (namely dirname = os.path.join(dirpath,dirname)) are a bit malformed. Here is one possible alternative – to test this, I used the full path to the directory as sys.argv[1], but you can make it more dynamic to suit your case. Also, avoid using variable names such as file since they are Python keywords. I couldn’t test out your grass.* functions, but hopefully this will be a clear enough example so you can tweak how you need. os.walk() natively handles a lot of standard parsing, so you can remove some of the directory-manipulating functions:

def import_tifs(dirpath):
  for dirpath, dirname, filenames in os.walk(dirpath):
    # Iterate through the files in the current dir returned by walk()
    for tif_file in filenames:
      # If the suffix is '.TIF', process
      if tif_file.upper().endswith('.tif'):
        # This will contain the full path to your file
        full_path = os.path.join(dirpath, tif_file)

        # tif_file will already contain the name, so you can call from here
        grass.message('Importing %s -> %s@%s...' % (full_path, tif_file, dirpath))

        grass.run_command('r.in.gdal',
                          flags = 'o',
                          input = full_path,
                          output = tif_file,
                          quiet = True,
                          overwrite = True)