Filter script for exercise code

Annotate your code with simple control keywords to maintain/extract exercise and solution versions of the same code in/from one file.

Syntax

@SOLUTION
<solution code>

@EXERCISE
<exercise code>

@DEV
<development code>

@=== or @===?

Respective sections (@SOLUTION, @EXERCISE or @DEV) may appear in any order, each starting with any of these control keywords, and must end with a line containing @=== or @===?.

Lines with control keywords are always removed entirely in the output.

You don't have to, for the filter script to work, but to be able to still directly run the annotated development code you will want to put the control keywords in comments.
Also, most of the time, exercise code sections are best placed in (block) comments.

Options

(at the beginning of filter.py)

supported — File (extensions) that should be processed and the corresponding comment style (for question marks).

exclude_dirs_that_start_with — Exclude sub directories starting with any string from this list.

exclude_files_that_start_with — Exclude files starting with any string from this list.

_filter_exclude_dirs and
_filter_exclude_files — Files to look for in sub directories. If found, they are assumed to contain one string per line that should be added to the corresponding exclude_*_that_start_with list for the respective sub directory.

Running

> python filter.py <path/to/source/directory> [exercise | solution]

Depending on the second parameter, the following directories will be generated (if the parameter is omitted, both are generated):

path/to/source/directory_exercise
path/to/source/directory_solution

If the source directory name ends wtih "_" (underscore) the exercise output directory will not be suffixed with _exercise but the underscore will be removed:

path/to/source/directory

Code annotation examples (Python)

—————————————————————————————————————————————————————————————————————————
SOURCE                    -> EXERCISE                  -> SOLUTION
—————————————————————————————————————————————————————————————————————————

Remove solution code in exercise files:

# @SOLUTION
solution_code()           ->                           -> solution_code()
# @===

Replace solution code with dummy code in exercise files:

# @SOLUTION
solution_code()           -> dummy_code()              -> solution_code()
''' @EXERCISE
dummy_code()
@=== '''

Place code in both exercise and solution files but not in development code:

''' @SOLUTION @EXERCISE
non_dev_code()
@=== '''                  -> non_dev_code()            -> non_dev_code()

Remove development code in both exercise and solution files:

# @DEV
dev_code()                ->                           ->
# @===

Replace development code with actual code in both exercise and solution files:

''' @SOLUTION @EXERCISE
actual_code()             -> actual_code()             -> actual_code()
@DEV '''
dev_code()
# @===

End code sections with @===? instead of @=== to insert question marks in exercise files:

# @SOLUTION               -> #                         -> solution_code()
solution_code()              # ???
# @===?                      #