In Python you can choose whether you want to indent your code using spaces or tabs. However, mixing the two can cause problems. Therefore, I made a simple Python script to fix mixed indentation.
Let's say that you want to change all tab-indents to space-indents (4 spaces wide).
fixindent -i my_input_script.py -s -w 4 -o my_output_script.py
Or, conversely, change all space-indents (8 spaces wide) into tabs. You also want to clean-up extraneous white-space etc. from the line-endings (-c):
fixindent -i my_input_script.py -t -w 8 -c -o my_output_script.py
You can also use pipelines (under Linux at least):
cat my_input_script.py | fixindent -t -c > my_output_script.py