279 lines
10 KiB
Python
279 lines
10 KiB
Python
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"""runpy.py - locating and running Python code using the module namespace
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Provides support for locating and running Python scripts using the Python
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module namespace instead of the native filesystem.
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This allows Python code to play nicely with non-filesystem based PEP 302
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importers when locating support scripts as well as when importing modules.
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"""
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# Written by Nick Coghlan <ncoghlan at gmail.com>
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# to implement PEP 338 (Executing Modules as Scripts)
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import sys
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import imp
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from pkgutil import read_code
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try:
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from imp import get_loader
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except ImportError:
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from pkgutil import get_loader
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__all__ = [
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"run_module", "run_path",
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]
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class _TempModule(object):
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"""Temporarily replace a module in sys.modules with an empty namespace"""
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def __init__(self, mod_name):
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self.mod_name = mod_name
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self.module = imp.new_module(mod_name)
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self._saved_module = []
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def __enter__(self):
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mod_name = self.mod_name
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try:
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self._saved_module.append(sys.modules[mod_name])
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except KeyError:
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pass
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sys.modules[mod_name] = self.module
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return self
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def __exit__(self, *args):
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if self._saved_module:
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sys.modules[self.mod_name] = self._saved_module[0]
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else:
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del sys.modules[self.mod_name]
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self._saved_module = []
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class _ModifiedArgv0(object):
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def __init__(self, value):
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self.value = value
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self._saved_value = self._sentinel = object()
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def __enter__(self):
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if self._saved_value is not self._sentinel:
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raise RuntimeError("Already preserving saved value")
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self._saved_value = sys.argv[0]
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sys.argv[0] = self.value
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def __exit__(self, *args):
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self.value = self._sentinel
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sys.argv[0] = self._saved_value
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def _run_code(code, run_globals, init_globals=None,
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mod_name=None, mod_fname=None,
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mod_loader=None, pkg_name=None):
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"""Helper to run code in nominated namespace"""
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if init_globals is not None:
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run_globals.update(init_globals)
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run_globals.update(__name__ = mod_name,
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__file__ = mod_fname,
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__loader__ = mod_loader,
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__package__ = pkg_name)
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exec code in run_globals
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return run_globals
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def _run_module_code(code, init_globals=None,
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mod_name=None, mod_fname=None,
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mod_loader=None, pkg_name=None):
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"""Helper to run code in new namespace with sys modified"""
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with _TempModule(mod_name) as temp_module, _ModifiedArgv0(mod_fname):
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mod_globals = temp_module.module.__dict__
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_run_code(code, mod_globals, init_globals,
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mod_name, mod_fname, mod_loader, pkg_name)
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# Copy the globals of the temporary module, as they
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# may be cleared when the temporary module goes away
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return mod_globals.copy()
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# This helper is needed due to a missing component in the PEP 302
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# loader protocol (specifically, "get_filename" is non-standard)
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# Since we can't introduce new features in maintenance releases,
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# support was added to zipimporter under the name '_get_filename'
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def _get_filename(loader, mod_name):
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for attr in ("get_filename", "_get_filename"):
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meth = getattr(loader, attr, None)
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if meth is not None:
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return meth(mod_name)
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return None
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# Helper to get the loader, code and filename for a module
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def _get_module_details(mod_name):
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loader = get_loader(mod_name)
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if loader is None:
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raise ImportError("No module named %s" % mod_name)
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if loader.is_package(mod_name):
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if mod_name == "__main__" or mod_name.endswith(".__main__"):
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raise ImportError("Cannot use package as __main__ module")
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try:
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pkg_main_name = mod_name + ".__main__"
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return _get_module_details(pkg_main_name)
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except ImportError, e:
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raise ImportError(("%s; %r is a package and cannot " +
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"be directly executed") %(e, mod_name))
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code = loader.get_code(mod_name)
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if code is None:
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raise ImportError("No code object available for %s" % mod_name)
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filename = _get_filename(loader, mod_name)
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return mod_name, loader, code, filename
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def _get_main_module_details():
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# Helper that gives a nicer error message when attempting to
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# execute a zipfile or directory by invoking __main__.py
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main_name = "__main__"
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try:
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return _get_module_details(main_name)
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except ImportError as exc:
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if main_name in str(exc):
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raise ImportError("can't find %r module in %r" %
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(main_name, sys.path[0]))
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raise
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# This function is the actual implementation of the -m switch and direct
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# execution of zipfiles and directories and is deliberately kept private.
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# This avoids a repeat of the situation where run_module() no longer met the
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# needs of mainmodule.c, but couldn't be changed because it was public
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def _run_module_as_main(mod_name, alter_argv=True):
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"""Runs the designated module in the __main__ namespace
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Note that the executed module will have full access to the
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__main__ namespace. If this is not desirable, the run_module()
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function should be used to run the module code in a fresh namespace.
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At the very least, these variables in __main__ will be overwritten:
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__name__
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__file__
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__loader__
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__package__
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"""
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try:
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if alter_argv or mod_name != "__main__": # i.e. -m switch
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mod_name, loader, code, fname = _get_module_details(mod_name)
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else: # i.e. directory or zipfile execution
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mod_name, loader, code, fname = _get_main_module_details()
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except ImportError as exc:
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msg = "%s: %s" % (sys.executable, str(exc))
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sys.exit(msg)
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pkg_name = mod_name.rpartition('.')[0]
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main_globals = sys.modules["__main__"].__dict__
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if alter_argv:
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sys.argv[0] = fname
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return _run_code(code, main_globals, None,
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"__main__", fname, loader, pkg_name)
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def run_module(mod_name, init_globals=None,
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run_name=None, alter_sys=False):
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"""Execute a module's code without importing it
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Returns the resulting top level namespace dictionary
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"""
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mod_name, loader, code, fname = _get_module_details(mod_name)
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if run_name is None:
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run_name = mod_name
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pkg_name = mod_name.rpartition('.')[0]
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if alter_sys:
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return _run_module_code(code, init_globals, run_name,
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fname, loader, pkg_name)
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else:
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# Leave the sys module alone
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return _run_code(code, {}, init_globals, run_name,
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fname, loader, pkg_name)
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# XXX (ncoghlan): Perhaps expose the C API function
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# as imp.get_importer instead of reimplementing it in Python?
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def _get_importer(path_name):
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"""Python version of PyImport_GetImporter C API function"""
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cache = sys.path_importer_cache
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try:
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importer = cache[path_name]
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except KeyError:
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# Not yet cached. Flag as using the
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# standard machinery until we finish
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# checking the hooks
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cache[path_name] = None
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for hook in sys.path_hooks:
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try:
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importer = hook(path_name)
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break
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except ImportError:
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pass
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else:
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# The following check looks a bit odd. The trick is that
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# NullImporter raises ImportError if the supplied path is a
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# *valid* directory entry (and hence able to be handled
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# by the standard import machinery)
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try:
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importer = imp.NullImporter(path_name)
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except ImportError:
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return None
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cache[path_name] = importer
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return importer
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def _get_code_from_file(fname):
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# Check for a compiled file first
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with open(fname, "rb") as f:
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code = read_code(f)
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if code is None:
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# That didn't work, so try it as normal source code
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with open(fname, "rU") as f:
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code = compile(f.read(), fname, 'exec')
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return code
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def run_path(path_name, init_globals=None, run_name=None):
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"""Execute code located at the specified filesystem location
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Returns the resulting top level namespace dictionary
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The file path may refer directly to a Python script (i.e.
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one that could be directly executed with execfile) or else
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it may refer to a zipfile or directory containing a top
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level __main__.py script.
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"""
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if run_name is None:
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run_name = "<run_path>"
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importer = _get_importer(path_name)
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if isinstance(importer, imp.NullImporter):
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# Not a valid sys.path entry, so run the code directly
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# execfile() doesn't help as we want to allow compiled files
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code = _get_code_from_file(path_name)
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return _run_module_code(code, init_globals, run_name, path_name)
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else:
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# Importer is defined for path, so add it to
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# the start of sys.path
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sys.path.insert(0, path_name)
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try:
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# Here's where things are a little different from the run_module
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# case. There, we only had to replace the module in sys while the
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# code was running and doing so was somewhat optional. Here, we
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# have no choice and we have to remove it even while we read the
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# code. If we don't do this, a __loader__ attribute in the
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# existing __main__ module may prevent location of the new module.
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main_name = "__main__"
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saved_main = sys.modules[main_name]
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del sys.modules[main_name]
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try:
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mod_name, loader, code, fname = _get_main_module_details()
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finally:
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sys.modules[main_name] = saved_main
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pkg_name = ""
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with _TempModule(run_name) as temp_module, \
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_ModifiedArgv0(path_name):
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mod_globals = temp_module.module.__dict__
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return _run_code(code, mod_globals, init_globals,
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run_name, fname, loader, pkg_name).copy()
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finally:
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try:
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sys.path.remove(path_name)
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except ValueError:
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pass
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if __name__ == "__main__":
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# Run the module specified as the next command line argument
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if len(sys.argv) < 2:
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print >> sys.stderr, "No module specified for execution"
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else:
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del sys.argv[0] # Make the requested module sys.argv[0]
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_run_module_as_main(sys.argv[0])
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