Question

(I foresaw this problem might happen 3 months ago, and was told to be diligent to avoid it. Yesterday, I was bitten by it, hard, and now that it has cost me real money, I am keen to fix it.)

If I move one of my Python source files into another directory, I need to remember to tell Mercurial that it moved (hg move).

When I deploy the new software to my server with Mercurial, it carefully deletes the old Python file and creates it in the new directory.

However, Mercurial is unaware of the pyc file in the same directory, and leaves it behind. The old pyc is used preferentially over new python file by other modules in the same directory.

What ensues is NOT hilarity.

How can I persuade Mercurial to automatically delete my old pyc file when I move the python file? Is there another better practice? Trying to remember to delete the pyc file from all the Mercurial repositories isn’t working.

Answer 1

What I have actually done:

1) I am considering Nicholas Knight’s suggestion about using a proper deployment strategy. I have been reading about Buildout and Collective.hostout to learn more. I need to decide whether such heavy-weight strategies are worthwhile for my project’s relatively simple requirements.

2) I have adopted Ry4an’s update hook concept, in the short-term, until I decide.

3) I ignored Ry4an’s warning about overkill, and wrote a Python script to only delete stray .pyc files.

#!/usr/bin/env python
""" Searches subdirectories of the current directory looking for .pyc files which
    do not have matching .py files, and deletes them.

    This is useful as a hook for version control when Python files are moved.
    It is dangerous for projects that deliberately include Python 
    binaries without source.
"""
import os
import os.path
for root, dirs, files in os.walk("."):
    pyc_files = filter(lambda filename: filename.endswith(".pyc"), files)
    py_files = set(filter(lambda filename: filename.endswith(".py"), files))
    excess_pyc_files = filter(lambda pyc_filename: pyc_filename[:-1] not in py_files, pyc_files)
    for excess_pyc_file in excess_pyc_files:
        full_path = os.path.join(root, excess_pyc_file)
        print "Removing old PYC file:", full_path
        os.remove(full_path)

My update hooks now call this rather than the “find” commands suggested by others.