Rename output shapefiles in PyQGIS

Question

I have a shapefile which resides in a folder, gets processed and the output is saved in another folder. Before the output, I would like to rename the shapefile slightly differently from the original:

eg.

"France (A).shp" -> "France (B).shp"

The following is the script I am using but comes up with a "cannot find file" error:

root_dir = "C:\Users\xxxx\Desktop\Test\\"
original_dir = 'Original files'
processed_dir = 'Processed files'

outputs_1=general.runalg("qgis:creategrid", 1000, 1000, 24108, 18351.157175, 258293.802316, 665638.226408, 1, 'EPSG:7405', None)

for path, subdirs, files in os.walk(root_dir):
    if original_dir in path:
        for file in files:
            if file.endswith('.shp'):
                newFile = rename(file, file.replace("(O).shp", "(P).shp"))
                outputs_2=general.runalg("qgis:clip", outputs_1['SAVENAME'], os.path.join(os.path.dirname(path), original_dir, file), os.path.join(os.path.dirname(path), processed_dir, newFile)

Is this the right way to go about changing the filename?

I also checked stackoverflow for some tips.

Answer 1

Following the idea from Cannot rename output file using standalone script for QGIS, I would do something like this:

for file in files:
  if file.endswith('.shp'):
    pieces = list(os.path.splitext(file)) 
    pieces[0]=pieces[0][:-3]+"(B)" 
    newFile = "".join(pieces)
    outputs_2=general.runalg("qgis:clip", outputs_1['SAVENAME'], os.path.join(os.path.dirname(path), original_dir, file), os.path.join(os.path.dirname(path), processed_dir, newFile)

This way you get the name of the file (with no extension), remove the last 3 characters (i.e., "(A)") and add the new ones (i.e., "(B)"). Then you add the extension and pass the new file name to the processing algorithm.