Source code for gluon.custom_import

#!/usr/bin/env python
# -*- coding: utf-8 -*-
| This file is part of the web2py Web Framework
| Copyrighted by Massimo Di Pierro <>
| License: LGPLv3 (

Support for smart import syntax for web2py applications
import __builtin__
import os
import sys
import threading
from gluon import current

NATIVE_IMPORTER = __builtin__.__import__
INVALID_MODULES = set(('', 'gluon', 'applications', 'custom_import'))

# backward compatibility API

[docs]def custom_import_install(): if __builtin__.__import__ == NATIVE_IMPORTER: INVALID_MODULES.update(sys.modules.keys()) __builtin__.__import__ = custom_importer
[docs]def track_changes(track=True): assert track in (True, False), "must be True or False" current.request._custom_import_track_changes = track
[docs]def is_tracking_changes(): return current.request._custom_import_track_changes
[docs]class CustomImportException(ImportError): pass
[docs]def custom_importer(name, globals=None, locals=None, fromlist=None, level=-1): """ web2py's custom importer. It behaves like the standard Python importer but it tries to transform import statements as something like "import applications.app_name.modules.x". If the import fails, it falls back on naive_importer """ if isinstance(name, unicode): name = name.encode('utf8') globals = globals or {} locals = locals or {} fromlist = fromlist or [] try: if current.request._custom_import_track_changes: base_importer = TRACK_IMPORTER else: base_importer = NATIVE_IMPORTER except: # there is no current.request (should never happen) base_importer = NATIVE_IMPORTER # if not relative and not from applications: if hasattr(current, 'request') \ and level <= 0 \ and not name.partition('.')[0] in INVALID_MODULES \ and isinstance(globals, dict): import_tb = None try: try: oname = name if not name.startswith('.') else '.'+name return NATIVE_IMPORTER(oname, globals, locals, fromlist, level) except ImportError: items = current.request.folder.split(os.path.sep) if not items[-1]: items = items[:-1] modules_prefix = '.'.join(items[-2:]) + '.modules' if not fromlist: # import like "import x" or "import x.y" result = None for itemname in name.split("."): new_mod = base_importer( modules_prefix, globals, locals, [itemname], level) try: result = result or sys.modules[modules_prefix+'.'+itemname] except KeyError, e: raise ImportError, 'Cannot import module %s' % str(e) modules_prefix += "." + itemname return result else: # import like "from x import a, b, ..." pname = modules_prefix + "." + name return base_importer(pname, globals, locals, fromlist, level) except ImportError, e1: import_tb = sys.exc_info()[2] try: return NATIVE_IMPORTER(name, globals, locals, fromlist, level) except ImportError, e3: raise ImportError, e1, import_tb # there an import error in the module except Exception, e2: raise # there is an error in the module finally: if import_tb: import_tb = None return NATIVE_IMPORTER(name, globals, locals, fromlist, level)
[docs]class TrackImporter(object): """ An importer tracking the date of the module files and reloading them when they are changed. """ THREAD_LOCAL = threading.local() PACKAGE_PATH_SUFFIX = os.path.sep + "" def __init__(self): self._import_dates = {} # Import dates of the files of the modules def __call__(self, name, globals=None, locals=None, fromlist=None, level=-1): """ The import method itself. """ globals = globals or {} locals = locals or {} fromlist = fromlist or [] try: # Check the date and reload if needed: self._update_dates(name, globals, locals, fromlist, level) # Try to load the module and update the dates if it works: result = NATIVE_IMPORTER(name, globals, locals, fromlist, level) # Module maybe loaded for the 1st time so we need to set the date self._update_dates(name, globals, locals, fromlist, level) return result except Exception, e: raise # Don't hide something that went wrong def _update_dates(self, name, globals, locals, fromlist, level): """ Update all the dates associated to the statement import. A single import statement may import many modules. """ self._reload_check(name, globals, locals, level) for fromlist_name in fromlist or []: pname = "%s.%s" % (name, fromlist_name) self._reload_check(pname, globals, locals, level) def _reload_check(self, name, globals, locals, level): """ Update the date associated to the module and reload the module if the file changed. """ module = sys.modules.get(name) file = self._get_module_file(module) if file: date = self._import_dates.get(file) new_date = None reload_mod = False mod_to_pack = False # Module turning into a package? (special case) try: new_date = os.path.getmtime(file) except: self._import_dates.pop(file, None) # Clean up # Handle module changing in package and #package changing in module: if file.endswith(".py"): # Get path without file ext: file = os.path.splitext(file)[0] reload_mod = os.path.isdir(file) \ and os.path.isfile(file + self.PACKAGE_PATH_SUFFIX) mod_to_pack = reload_mod else: # Package turning into module? file += ".py" reload_mod = os.path.isfile(file) if reload_mod: new_date = os.path.getmtime(file) # Refresh file date if reload_mod or not date or new_date > date: self._import_dates[file] = new_date if reload_mod or (date and new_date > date): if mod_to_pack: # Module turning into a package: mod_name = module.__name__ del sys.modules[mod_name] # Delete the module # Reload the module: NATIVE_IMPORTER(mod_name, globals, locals, [], level) else: reload(module) def _get_module_file(self, module): """ Get the absolute path file associated to the module or None. """ file = getattr(module, "__file__", None) if file: # Make path absolute if not: file = os.path.splitext(file)[0] + ".py" # Change .pyc for .py if file.endswith(self.PACKAGE_PATH_SUFFIX): file = os.path.dirname(file) # Track dir for packages return file
TRACK_IMPORTER = TrackImporter()