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 from pkgutil import read_code 15 try: 16 from imp import get_loader 17 except ImportError: 18 from pkgutil import get_loader 19 20 __all__ = [ 21 "run_module", "run_path", 22 ] 23 24 class _TempModule(object): 25 """Temporarily replace a module in sys.modules with an empty namespace""" 26 def __init__(self, mod_name): 27 self.mod_name = mod_name 28 self.module = imp.new_module(mod_name) 29 self._saved_module = [] 30 31 def __enter__(self): 32 mod_name = self.mod_name 33 try: 34 self._saved_module.append(sys.modules[mod_name]) 35 except KeyError: 36 pass 37 sys.modules[mod_name] = self.module 38 return self 39 40 def __exit__(self, *args): 41 if self._saved_module: 42 sys.modules[self.mod_name] = self._saved_module[0] 43 else: 44 del sys.modules[self.mod_name] 45 self._saved_module = [] 46 47 class _ModifiedArgv0(object): 48 def __init__(self, value): 49 self.value = value 50 self._saved_value = self._sentinel = object() 51 52 def __enter__(self): 53 if self._saved_value is not self._sentinel: 54 raise RuntimeError("Already preserving saved value") 55 self._saved_value = sys.argv[0] 56 sys.argv[0] = self.value 57 58 def __exit__(self, *args): 59 self.value = self._sentinel 60 sys.argv[0] = self._saved_value 61 62 def _run_code(code, run_globals, init_globals=None, 63 mod_name=None, mod_fname=None, 64 mod_loader=None, pkg_name=None): 65 """Helper to run code in nominated namespace""" 66 if init_globals is not None: 67 run_globals.update(init_globals) 68 run_globals.update(__name__ = mod_name, 69 __file__ = mod_fname, 70 __loader__ = mod_loader, 71 __package__ = pkg_name) 72 exec code in run_globals 73 return run_globals 74 75 def _run_module_code(code, init_globals=None, 76 mod_name=None, mod_fname=None, 77 mod_loader=None, pkg_name=None): 78 """Helper to run code in new namespace with sys modified""" 79 with _TempModule(mod_name) as temp_module, _ModifiedArgv0(mod_fname): 80 mod_globals = temp_module.module.__dict__ 81 _run_code(code, mod_globals, init_globals, 82 mod_name, mod_fname, mod_loader, pkg_name) 83 # Copy the globals of the temporary module, as they 84 # may be cleared when the temporary module goes away 85 return mod_globals.copy() 86 87 88 # This helper is needed due to a missing component in the PEP 302 89 # loader protocol (specifically, "get_filename" is non-standard) 90 # Since we can't introduce new features in maintenance releases, 91 # support was added to zipimporter under the name '_get_filename' 92 def _get_filename(loader, mod_name): 93 for attr in ("get_filename", "_get_filename"): 94 meth = getattr(loader, attr, None) 95 if meth is not None: 96 return meth(mod_name) 97 return None 98 99 # Helper to get the loader, code and filename for a module 100 def _get_module_details(mod_name): 101 loader = get_loader(mod_name) 102 if loader is None: 103 raise ImportError("No module named %s" % mod_name) 104 if loader.is_package(mod_name): 105 if mod_name == "__main__" or mod_name.endswith(".__main__"): 106 raise ImportError("Cannot use package as __main__ module") 107 try: 108 pkg_main_name = mod_name + ".__main__" 109 return _get_module_details(pkg_main_name) 110 except ImportError, e: 111 raise ImportError(("%s; %r is a package and cannot " + 112 "be directly executed") %(e, mod_name)) 113 code = loader.get_code(mod_name) 114 if code is None: 115 raise ImportError("No code object available for %s" % mod_name) 116 filename = _get_filename(loader, mod_name) 117 return mod_name, loader, code, filename 118 119 120 def _get_main_module_details(): 121 # Helper that gives a nicer error message when attempting to 122 # execute a zipfile or directory by invoking __main__.py 123 main_name = "__main__" 124 try: 125 return _get_module_details(main_name) 126 except ImportError as exc: 127 if main_name in str(exc): 128 raise ImportError("can't find %r module in %r" % 129 (main_name, sys.path[0])) 130 raise 131 132 # This function is the actual implementation of the -m switch and direct 133 # execution of zipfiles and directories and is deliberately kept private. 134 # This avoids a repeat of the situation where run_module() no longer met the 135 # needs of mainmodule.c, but couldn't be changed because it was public 136 def _run_module_as_main(mod_name, alter_argv=True): 137 """Runs the designated module in the __main__ namespace 138 139 Note that the executed module will have full access to the 140 __main__ namespace. If this is not desirable, the run_module() 141 function should be used to run the module code in a fresh namespace. 142 143 At the very least, these variables in __main__ will be overwritten: 144 __name__ 145 __file__ 146 __loader__ 147 __package__ 148 """ 149 try: 150 if alter_argv or mod_name != "__main__": # i.e. -m switch 151 mod_name, loader, code, fname = _get_module_details(mod_name) 152 else: # i.e. directory or zipfile execution 153 mod_name, loader, code, fname = _get_main_module_details() 154 except ImportError as exc: 155 msg = "%s: %s" % (sys.executable, str(exc)) 156 sys.exit(msg) 157 pkg_name = mod_name.rpartition('.')[0] 158 main_globals = sys.modules["__main__"].__dict__ 159 if alter_argv: 160 sys.argv[0] = fname 161 return _run_code(code, main_globals, None, 162 "__main__", fname, loader, pkg_name) 163 164 def run_module(mod_name, init_globals=None, 165 run_name=None, alter_sys=False): 166 """Execute a module's code without importing it 167 168 Returns the resulting top level namespace dictionary 169 """ 170 mod_name, loader, code, fname = _get_module_details(mod_name) 171 if run_name is None: 172 run_name = mod_name 173 pkg_name = mod_name.rpartition('.')[0] 174 if alter_sys: 175 return _run_module_code(code, init_globals, run_name, 176 fname, loader, pkg_name) 177 else: 178 # Leave the sys module alone 179 return _run_code(code, {}, init_globals, run_name, 180 fname, loader, pkg_name) 181 182 183 # XXX (ncoghlan): Perhaps expose the C API function 184 # as imp.get_importer instead of reimplementing it in Python? 185 def _get_importer(path_name): 186 """Python version of PyImport_GetImporter C API function""" 187 cache = sys.path_importer_cache 188 try: 189 importer = cache[path_name] 190 except KeyError: 191 # Not yet cached. Flag as using the 192 # standard machinery until we finish 193 # checking the hooks 194 cache[path_name] = None 195 for hook in sys.path_hooks: 196 try: 197 importer = hook(path_name) 198 break 199 except ImportError: 200 pass 201 else: 202 # The following check looks a bit odd. The trick is that 203 # NullImporter throws ImportError if the supplied path is a 204 # *valid* directory entry (and hence able to be handled 205 # by the standard import machinery) 206 try: 207 importer = imp.NullImporter(path_name) 208 except ImportError: 209 return None 210 cache[path_name] = importer 211 return importer 212 213 def _get_code_from_file(fname): 214 # Check for a compiled file first 215 with open(fname, "rb") as f: 216 code = read_code(f) 217 if code is None: 218 # That didn't work, so try it as normal source code 219 with open(fname, "rU") as f: 220 code = compile(f.read(), fname, 'exec') 221 return code 222 223 def run_path(path_name, init_globals=None, run_name=None): 224 """Execute code located at the specified filesystem location 225 226 Returns the resulting top level namespace dictionary 227 228 The file path may refer directly to a Python script (i.e. 229 one that could be directly executed with execfile) or else 230 it may refer to a zipfile or directory containing a top 231 level __main__.py script. 232 """ 233 if run_name is None: 234 run_name = "<run_path>" 235 importer = _get_importer(path_name) 236 if isinstance(importer, imp.NullImporter): 237 # Not a valid sys.path entry, so run the code directly 238 # execfile() doesn't help as we want to allow compiled files 239 code = _get_code_from_file(path_name) 240 return _run_module_code(code, init_globals, run_name, path_name) 241 else: 242 # Importer is defined for path, so add it to 243 # the start of sys.path 244 sys.path.insert(0, path_name) 245 try: 246 # Here's where things are a little different from the run_module 247 # case. There, we only had to replace the module in sys while the 248 # code was running and doing so was somewhat optional. Here, we 249 # have no choice and we have to remove it even while we read the 250 # code. If we don't do this, a __loader__ attribute in the 251 # existing __main__ module may prevent location of the new module. 252 main_name = "__main__" 253 saved_main = sys.modules[main_name] 254 del sys.modules[main_name] 255 try: 256 mod_name, loader, code, fname = _get_main_module_details() 257 finally: 258 sys.modules[main_name] = saved_main 259 pkg_name = "" 260 with _TempModule(run_name) as temp_module, \ 261 _ModifiedArgv0(path_name): 262 mod_globals = temp_module.module.__dict__ 263 return _run_code(code, mod_globals, init_globals, 264 run_name, fname, loader, pkg_name).copy() 265 finally: 266 try: 267 sys.path.remove(path_name) 268 except ValueError: 269 pass 270 271 272 if __name__ == "__main__": 273 # Run the module specified as the next command line argument 274 if len(sys.argv) < 2: 275 print >> sys.stderr, "No module specified for execution" 276 else: 277 del sys.argv[0] # Make the requested module sys.argv[0] 278 _run_module_as_main(sys.argv[0]) 279
