Fixed the lack of indexation of files.

Added comments.

main.py

@@ -1,19 +1,33 @@
 # This is a project for an automated file renamer
-# TODO: allow for the user to input the arguments using a console
 # TODO: implement GUI
+# TODO: make the empty-prefixed calls identity operations for those base directories
 
 import os
 
 
 def renamer(prefix, base_dir):
     for directory in os.listdir(base_dir):
-        if os.path.isdir(directory):
-            new_dir_name = prefix + '_' + directory
-            os.rename(directory, new_dir_name)
-            for file in os.listdir(directory):
-                new_file_name = directory + '/' + prefix + '_' + file
-                os.rename(directory + '/' + file, new_file_name)
+        if os.path.isdir(base_dir + '/' + directory):
+            for file in os.listdir(base_dir + '/' + directory):
+                if prefix != '':
+                    new_file_name = base_dir + '/' + directory + '/' + prefix + '_' + file
+                    os.rename(base_dir + '/' + directory + '/' + file, new_file_name)   # Adding a prefix
+                # TODO: probably worth it to find a good way to get rid of this 'if' block
+                if file[3].isalpha():   # Adding a corresponding number to the files with solutions
+                    tmp = ''
+                    for char in directory:
+                        if char.isdigit():
+                            tmp += char
+                    if tmp != '':
+                        tmp += '_'
+                    new_name = file[:3] + tmp + file[3:]    # The 'cutting' point should not be at index 3, but after
+                                                            # the prefix
+                    os.rename(base_dir + '/' + directory + '/' + file, base_dir + '/' + directory + '/' + new_name)
+            new_dir_name = base_dir + '/' + prefix + '_' + directory
+            os.rename(base_dir + '/' + directory, new_dir_name)
 
 
 if __name__ == '__main__':
-    pass
+    prefix = input("Prefix: ")
+    base_dir = input("Base directory: ")
+    renamer(prefix, base_dir)