Lib/runpy.py

   1 """runpy.py - locating and running Python code using the module namespace
   2
   3 Provides support for locating and running Python scripts using the Python
   4 module namespace instead of the native filesystem.
   5
   6 This allows Python code to play nicely with non-filesystem based PEP 302
   7 importers when locating support scripts as well as when importing modules.
   8 """
   9 # Written by Nick Coghlan <ncoghlan at gmail.com>
  10 #    to implement PEP 338 (Executing Modules as Scripts)
  11
  12 import sys
  13 import imp
  14 try:
  15     from imp import get_loader
  16 except ImportError:
  17     from pkgutil import get_loader
  18
  19 __all__ = [
  20     "run_module",
  21 ]
  22
  23
  24 def _run_code(code, run_globals, init_globals=None,
  25               mod_name=None, mod_fname=None,
  26               mod_loader=None, pkg_name=None):
  27     """Helper for _run_module_code"""
  28     if init_globals is not None:
  29         run_globals.update(init_globals)
  30     run_globals.update(__name__ = mod_name,
  31                        __file__ = mod_fname,
  32                        __loader__ = mod_loader,
  33                        __package__ = pkg_name)
  34     exec(code, run_globals)
  35     return run_globals
  36
  37 def _run_module_code(code, init_globals=None,
  38                     mod_name=None, mod_fname=None,
  39                     mod_loader=None, pkg_name=None):
  40     """Helper for run_module"""
  41     # Set up the top level namespace dictionary
  42     temp_module = imp.new_module(mod_name)
  43     mod_globals = temp_module.__dict__
  44     # Modify sys.argv[0] and sys.module[mod_name]
  45     saved_argv0 = sys.argv[0]
  46     restore_module = mod_name in sys.modules
  47     if restore_module:
  48         saved_module = sys.modules[mod_name]
  49     sys.argv[0] = mod_fname
  50     sys.modules[mod_name] = temp_module
  51     try:
  52         _run_code(code, mod_globals, init_globals,
  53                     mod_name, mod_fname,
  54                     mod_loader, pkg_name)
  55     finally:
  56         sys.argv[0] = saved_argv0
  57         if restore_module:
  58             sys.modules[mod_name] = saved_module
  59         else:
  60             del sys.modules[mod_name]
  61     # Copy the globals of the temporary module, as they
  62     # may be cleared when the temporary module goes away
  63     return mod_globals.copy()
  64
  65
  66 # This helper is needed due to a missing component in the PEP 302
  67 # loader protocol (specifically, "get_filename" is non-standard)
  68 def _get_filename(loader, mod_name):
  69     try:
  70         get_filename = loader.get_filename
  71     except AttributeError:
  72         return None
  73     else:
  74         return get_filename(mod_name)
  75
  76 # Helper to get the loader, code and filename for a module
  77 def _get_module_details(mod_name):
  78     loader = get_loader(mod_name)
  79     if loader is None:
  80         raise ImportError("No module named %s" % mod_name)
  81     if loader.is_package(mod_name):
  82         raise ImportError(("%s is a package and cannot " +
  83                           "be directly executed") % mod_name)
  84     code = loader.get_code(mod_name)
  85     if code is None:
  86         raise ImportError("No code object available for %s" % mod_name)
  87     filename = _get_filename(loader, mod_name)
  88     return loader, code, filename
  89
  90
  91 # XXX ncoghlan: Should this be documented and made public?
  92 # (Current thoughts: don't repeat the mistake that lead to its
  93 # creation when run_module() no longer met the needs of
  94 # mainmodule.c, but couldn't be changed because it was public)
  95 def _run_module_as_main(mod_name, set_argv0=True):
  96     """Runs the designated module in the __main__ namespace
  97
  98        These __*__ magic variables will be overwritten:
  99            __file__
 100            __loader__
 101     """
 102     try:
 103         loader, code, fname = _get_module_details(mod_name)
 104     except ImportError as exc:
 105         # Try to provide a good error message
 106         # for directories, zip files and the -m switch
 107         if set_argv0:
 108             # For -m switch, just disply the exception
 109             info = str(exc)
 110         else:
 111             # For directories/zipfiles, let the user
 112             # know what the code was looking for
 113             info = "can't find '__main__.py' in %r" % sys.argv[0]
 114         msg = "%s: %s" % (sys.executable, info)
 115         sys.exit(msg)
 116     pkg_name = mod_name.rpartition('.')[0]
 117     main_globals = sys.modules["__main__"].__dict__
 118     if set_argv0:
 119         sys.argv[0] = fname
 120     return _run_code(code, main_globals, None,
 121                      "__main__", fname, loader, pkg_name)
 122
 123 def run_module(mod_name, init_globals=None,
 124                run_name=None, alter_sys=False):
 125     """Execute a module's code without importing it
 126
 127        Returns the resulting top level namespace dictionary
 128     """
 129     loader, code, fname = _get_module_details(mod_name)
 130     if run_name is None:
 131         run_name = mod_name
 132     pkg_name = mod_name.rpartition('.')[0]
 133     if alter_sys:
 134         return _run_module_code(code, init_globals, run_name,
 135                                 fname, loader, pkg_name)
 136     else:
 137         # Leave the sys module alone
 138         return _run_code(code, {}, init_globals, run_name,
 139                          fname, loader, pkg_name)
 140
 141
 142 if __name__ == "__main__":
 143     # Run the module specified as the next command line argument
 144     if len(sys.argv) < 2:
 145         print("No module specified for execution", file=sys.stderr)
 146     else:
 147         del sys.argv[0] # Make the requested module sys.argv[0]
 148         _run_module_as_main(sys.argv[0])