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ihooks.py
"""Import hook support. Consistent use of this module will make it possible to change the different mechanisms involved in loading modules independently. While the built-in module imp exports interfaces to the built-in module searching and loading algorithm, and it is possible to replace the built-in function __import__ in order to change the semantics of the import statement, until now it has been difficult to combine the effect of different __import__ hacks, like loading modules from URLs by rimport.py, or restricted execution by rexec.py. This module defines three new concepts: 1) A "file system hooks" class provides an interface to a filesystem. One hooks class is defined (Hooks), which uses the interface provided by standard modules os and os.path. It should be used as the base class for other hooks classes. 2) A "module loader" class provides an interface to search for a module in a search path and to load it. It defines a method which searches for a module in a single directory; by overriding this method one can redefine the details of the search. If the directory is None, built-in and frozen modules are searched instead. Two module loader class are defined, both implementing the search strategy used by the built-in __import__ function: ModuleLoader uses the imp module's find_module interface, while HookableModuleLoader uses a file system hooks class to interact with the file system. Both use the imp module's load_* interfaces to actually load the module. 3) A "module importer" class provides an interface to import a module, as well as interfaces to reload and unload a module. It also provides interfaces to install and uninstall itself instead of the default __import__ and reload (and unload) functions. One module importer class is defined (ModuleImporter), which uses a module loader instance passed in (by default HookableModuleLoader is instantiated). The classes defined here should be used as base classes for extended functionality along those lines. If a module importer class supports dotted names, its import_module() must return a different value depending on whether it is called on behalf of a "from ... import ..." statement or not. (This is caused by the way the __import__ hook is used by the Python interpreter.) It would also do wise to install a different version of reload(). """ from warnings import warnpy3k, warn warnpy3k("the ihooks module has been removed in Python 3.0", stacklevel=2) del warnpy3k import __builtin__ import imp import os import sys __all__ = ["BasicModuleLoader","Hooks","ModuleLoader","FancyModuleLoader", "BasicModuleImporter","ModuleImporter","install","uninstall"] VERBOSE = 0 from imp import C_EXTENSION, PY_SOURCE, PY_COMPILED from imp import C_BUILTIN, PY_FROZEN, PKG_DIRECTORY BUILTIN_MODULE = C_BUILTIN FROZEN_MODULE = PY_FROZEN class _Verbose: def __init__(self, verbose = VERBOSE): self.verbose = verbose def get_verbose(self): return self.verbose def set_verbose(self, verbose): self.verbose = verbose # XXX The following is an experimental interface def note(self, *args): if self.verbose: self.message(*args) def message(self, format, *args): if args: print format%args else: print format class BasicModuleLoader(_Verbose): """Basic module loader. This provides the same functionality as built-in import. It doesn't deal with checking sys.modules -- all it provides is find_module() and a load_module(), as well as find_module_in_dir() which searches just one directory, and can be overridden by a derived class to change the module search algorithm when the basic dependency on sys.path is unchanged. The interface is a little more convenient than imp's: find_module(name, [path]) returns None or 'stuff', and load_module(name, stuff) loads the module. """ def find_module(self, name, path = None): if path is None: path = [None] + self.default_path() for dir in path: stuff = self.find_module_in_dir(name, dir) if stuff: return stuff return None def default_path(self): return sys.path def find_module_in_dir(self, name, dir): if dir is None: return self.find_builtin_module(name) else: try: return imp.find_module(name, [dir]) except ImportError: return None def find_builtin_module(self, name): # XXX frozen packages? if imp.is_builtin(name): return None, '', ('', '', BUILTIN_MODULE) if imp.is_frozen(name): return None, '', ('', '', FROZEN_MODULE) return None def load_module(self, name, stuff): file, filename, info = stuff try: return imp.load_module(name, file, filename, info) finally: if file: file.close() class Hooks(_Verbose): """Hooks into the filesystem and interpreter. By deriving a subclass you can redefine your filesystem interface, e.g. to merge it with the URL space. This base class behaves just like the native filesystem. """ # imp interface def get_suffixes(self): return imp.get_suffixes() def new_module(self, name): return imp.new_module(name) def is_builtin(self, name): return imp.is_builtin(name) def init_builtin(self, name): return imp.init_builtin(name) def is_frozen(self, name): return imp.is_frozen(name) def init_frozen(self, name): return imp.init_frozen(name) def get_frozen_object(self, name): return imp.get_frozen_object(name) def load_source(self, name, filename, file=None): return imp.load_source(name, filename, file) def load_compiled(self, name, filename, file=None): return imp.load_compiled(name, filename, file) def load_dynamic(self, name, filename, file=None): return imp.load_dynamic(name, filename, file) def load_package(self, name, filename, file=None): return imp.load_module(name, file, filename, ("", "", PKG_DIRECTORY)) def add_module(self, name): d = self.modules_dict() if name in d: return d[name] d[name] = m = self.new_module(name) return m # sys interface def modules_dict(self): return sys.modules def default_path(self): return sys.path def path_split(self, x): return os.path.split(x) def path_join(self, x, y): return os.path.join(x, y) def path_isabs(self, x): return os.path.isabs(x) # etc. def path_exists(self, x): return os.path.exists(x) def path_isdir(self, x): return os.path.isdir(x) def path_isfile(self, x): return os.path.isfile(x) def path_islink(self, x): return os.path.islink(x) # etc. def openfile(self, *x): return open(*x) openfile_error = IOError def listdir(self, x): return os.listdir(x) listdir_error = os.error # etc. class ModuleLoader(BasicModuleLoader): """Default module loader; uses file system hooks. By defining suitable hooks, you might be able to load modules from other sources than the file system, e.g. from compressed or encrypted files, tar files or (if you're brave!) URLs. """ def __init__(self, hooks = None, verbose = VERBOSE): BasicModuleLoader.__init__(self, verbose) self.hooks = hooks or Hooks(verbose) def default_path(self): return self.hooks.default_path() def modules_dict(self): return self.hooks.modules_dict() def get_hooks(self): return self.hooks def set_hooks(self, hooks): self.hooks = hooks def find_builtin_module(self, name): # XXX frozen packages? if self.hooks.is_builtin(name): return None, '', ('', '', BUILTIN_MODULE) if self.hooks.is_frozen(name): return None, '', ('', '', FROZEN_MODULE) return None def find_module_in_dir(self, name, dir, allow_packages=1): if dir is None: return self.find_builtin_module(name) if allow_packages: fullname = self.hooks.path_join(dir, name) if self.hooks.path_isdir(fullname): stuff = self.find_module_in_dir("__init__", fullname, 0) if stuff: file = stuff[0] if file: file.close() return None, fullname, ('', '', PKG_DIRECTORY) for info in self.hooks.get_suffixes(): suff, mode, type = info fullname = self.hooks.path_join(dir, name+suff) try: fp = self.hooks.openfile(fullname, mode) return fp, fullname, info except self.hooks.openfile_error: pass return None def load_module(self, name, stuff): file, filename, info = stuff (suff, mode, type) = info try: if type == BUILTIN_MODULE: return self.hooks.init_builtin(name) if type == FROZEN_MODULE: return self.hooks.init_frozen(name) if type == C_EXTENSION: m = self.hooks.load_dynamic(name, filename, file) elif type == PY_SOURCE: m = self.hooks.load_source(name, filename, file) elif type == PY_COMPILED: m = self.hooks.load_compiled(name, filename, file) elif type == PKG_DIRECTORY: m = self.hooks.load_package(name, filename, file) else: raise ImportError, "Unrecognized module type (%r) for %s" % \ (type, name) finally: if file: file.close() m.__file__ = filename return m class FancyModuleLoader(ModuleLoader): """Fancy module loader -- parses and execs the code itself.""" def load_module(self, name, stuff): file, filename, (suff, mode, type) = stuff realfilename = filename path = None if type == PKG_DIRECTORY: initstuff = self.find_module_in_dir("__init__", filename, 0) if not initstuff: raise ImportError, "No __init__ module in package %s" % name initfile, initfilename, initinfo = initstuff initsuff, initmode, inittype = initinfo if inittype not in (PY_COMPILED, PY_SOURCE): if initfile: initfile.close() raise ImportError, \ "Bad type (%r) for __init__ module in package %s" % ( inittype, name) path = [filename] file = initfile realfilename = initfilename type = inittype if type == FROZEN_MODULE: code = self.hooks.get_frozen_object(name) elif type == PY_COMPILED: import marshal file.seek(8) code = marshal.load(file) elif type == PY_SOURCE: data = file.read() code = compile(data, realfilename, 'exec') else: return ModuleLoader.load_module(self, name, stuff) m = self.hooks.add_module(name) if path: m.__path__ = path m.__file__ = filename try: exec code in m.__dict__ except: d = self.hooks.modules_dict() if name in d: del d[name] raise return m class BasicModuleImporter(_Verbose): """Basic module importer; uses module loader. This provides basic import facilities but no package imports. """ def __init__(self, loader = None, verbose = VERBOSE): _Verbose.__init__(self, verbose) self.loader = loader or ModuleLoader(None, verbose) self.modules = self.loader.modules_dict() def get_loader(self): return self.loader def set_loader(self, loader): self.loader = loader def get_hooks(self): return self.loader.get_hooks() def set_hooks(self, hooks): return self.loader.set_hooks(hooks) def import_module(self, name, globals={}, locals={}, fromlist=[]): name = str(name) if name in self.modules: return self.modules[name] # Fast path stuff = self.loader.find_module(name) if not stuff: raise ImportError, "No module named %s" % name return self.loader.load_module(name, stuff) def reload(self, module, path = None): name = str(module.__name__) stuff = self.loader.find_module(name, path) if not stuff: raise ImportError, "Module %s not found for reload" % name return self.loader.load_module(name, stuff) def unload(self, module): del self.modules[str(module.__name__)] # XXX Should this try to clear the module's namespace? def install(self): self.save_import_module = __builtin__.__import__ self.save_reload = __builtin__.reload if not hasattr(__builtin__, 'unload'): __builtin__.unload = None self.save_unload = __builtin__.unload __builtin__.__import__ = self.import_module __builtin__.reload = self.reload __builtin__.unload = self.unload def uninstall(self): __builtin__.__import__ = self.save_import_module __builtin__.reload = self.save_reload __builtin__.unload = self.save_unload if not __builtin__.unload: del __builtin__.unload class ModuleImporter(BasicModuleImporter): """A module importer that supports packages.""" def import_module(self, name, globals=None, locals=None, fromlist=None, level=-1): parent = self.determine_parent(globals, level) q, tail = self.find_head_package(parent, str(name)) m = self.load_tail(q, tail) if not fromlist: return q if hasattr(m, "__path__"): self.ensure_fromlist(m, fromlist) return m def determine_parent(self, globals, level=-1): if not globals or not level: return None pkgname = globals.get('__package__') if pkgname is not None: if not pkgname and level > 0: raise ValueError, 'Attempted relative import in non-package' else: # __package__ not set, figure it out and set it modname = globals.get('__name__') if modname is None: return None if "__path__" in globals: # __path__ is set so modname is already the package name pkgname = modname else: # normal module, work out package name if any if '.' not in modname: if level > 0: raise ValueError, ('Attempted relative import in ' 'non-package') globals['__package__'] = None return None pkgname = modname.rpartition('.')[0] globals['__package__'] = pkgname if level > 0: dot = len(pkgname) for x in range(level, 1, -1): try: dot = pkgname.rindex('.', 0, dot) except ValueError: raise ValueError('attempted relative import beyond ' 'top-level package') pkgname = pkgname[:dot] try: return sys.modules[pkgname] except KeyError: if level < 1: warn("Parent module '%s' not found while handling " "absolute import" % pkgname, RuntimeWarning, 1) return None else: raise SystemError, ("Parent module '%s' not loaded, cannot " "perform relative import" % pkgname) def find_head_package(self, parent, name): if '.' in name: i = name.find('.') head = name[:i] tail = name[i+1:] else: head = name tail = "" if parent: qname = "%s.%s" % (parent.__name__, head) else: qname = head q = self.import_it(head, qname, parent) if q: return q, tail if parent: qname = head parent = None q = self.import_it(head, qname, parent) if q: return q, tail raise ImportError, "No module named '%s'" % qname def load_tail(self, q, tail): m = q while tail: i = tail.find('.') if i < 0: i = len(tail) head, tail = tail[:i], tail[i+1:] mname = "%s.%s" % (m.__name__, head) m = self.import_it(head, mname, m) if not m: raise ImportError, "No module named '%s'" % mname return m def ensure_fromlist(self, m, fromlist, recursive=0): for sub in fromlist: if sub == "*": if not recursive: try: all = m.__all__ except AttributeError: pass else: self.ensure_fromlist(m, all, 1) continue if sub != "*" and not hasattr(m, sub): subname = "%s.%s" % (m.__name__, sub) submod = self.import_it(sub, subname, m) if not submod: raise ImportError, "No module named '%s'" % subname def import_it(self, partname, fqname, parent, force_load=0): if not partname: # completely empty module name should only happen in # 'from . import' or __import__("") return parent if not force_load: try: return self.modules[fqname] except KeyError: pass try: path = parent and parent.__path__ except AttributeError: return None partname = str(partname) stuff = self.loader.find_module(partname, path) if not stuff: return None fqname = str(fqname) m = self.loader.load_module(fqname, stuff) if parent: setattr(parent, partname, m) return m def reload(self, module): name = str(module.__name__) if '.' not in name: return self.import_it(name, name, None, force_load=1) i = name.rfind('.') pname = name[:i] parent = self.modules[pname] return self.import_it(name[i+1:], name, parent, force_load=1) default_importer = None current_importer = None def install(importer = None): global current_importer current_importer = importer or default_importer or ModuleImporter() current_importer.install() def uninstall(): global current_importer current_importer.uninstall()
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