# In tools/, make a subdirectory _stable_1_0_2 containing the 1.0.2 stable # version of the "tools" package. Make _stable_1_0 and _stable_1 symlinks to that directory, # assuming you don't have any newer 1.0.x or 1.x releases. Also make a _latest_1_0_2 containing # the latest (possibly unstable) 1.0.2.x version, and symlink _latest_1_0 and _latest_1 to it. # Finally, create a _exact_1_0_2_4 if you have, for example, a 1.0.2.4 release of "tools". # # Each of those subdirectories is a package that can be loaded as "tools" by the client. # File: tools/__init__.py if '_original__import__' not in locals(): _original__import__ = __import__ def myimport(name, theglobals=None, thelocals=None, fromlist=None, level=-1): if name.split('.')[0] != "tools": return _original__import__(name, theglobals, thelocals, fromlist, level) if not currentversion: raise Exception("After importing tools, you must " "load a specific version by typing something like " "'tools = tools.loadstable(\"0.1\")' .") def withversion(name): """ Turn "tools[.anything]" into "[.anything]" , where is something like 'tools._stable_0_1' . """ parts = name.split('.') parts[0] = currentversion.__name__ # eg 'tools._stable_0_1' return '.'.join(parts) # "import tools[.whatever.whatever]" if not fromlist: # use instead of "tools", but otherwise execute the # import as expected _original__import__(withversion(name), theglobals, thelocals, fromlist, level) # but return as the top-level package instead of # returning tools as expected return currentversion # "from tools[.whatever.whatever] import thing": instead, # "from [.whatever.whatever] import thing", and # return thing as expected return _original__import__(withversion(name), theglobals, thelocals, fromlist, level) __builtins__["__import__"] = myimport def loadstable(ver): return _loadversion(ver, prefix="_stable_") def loadunstable(ver): return _loadversion(ver, prefix="_latest_") def loadexact(ver): return _loadversion(ver, prefix="_exact_") def _loadversion(ver, prefix): targetname = prefix + ver.replace('.', '_') mainpackage = _original__import__("tools", globals(), locals(), [targetname]) global currentversion currentversion = getattr(mainpackage, targetname) # Let users change versions after choosing this one currentversion.loadstable = loadstable currentversion.loadunstable = loadunstable currentversion.loadexact = loadexact return currentversion currentversion = None # In the user's code: # This line makes "tools" be the stable 1.0.2 release. import tools; tools = tools.loadstable('1') # Now the user can work with tools as normal from tools import foo import tools.bar.bim from tools.baz import bonk