PEP 3147 implementation

Lib/py_compile.py

 """Routine to "compile" a .py file to a .pyc (or .pyo) file.
 
 This module has intimate knowledge of the format of .pyc files.
 """
 
 import builtins
+import errno
 import imp
 import marshal
 import os
 import sys
 import tokenize
 import traceback
 
+from imp import cache_from_source

[Benjamin, 2010/04/07 02:50:04]

What's the benefit on having this in the module namespace when imp is already
imported above?

[barry, 2010/04/08 12:53:47]

Done.

+
 MAGIC = imp.get_magic()
 
 __all__ = ["compile", "main", "PyCompileError"]
 
 
 class PyCompileError(Exception):
     """Exception raised when an error occurs while attempting to
     compile the file.
 
     To raise this exception, use
 
         raise PyCompileError(exc_type,exc_value,file[,msg])
 
     where
 
         exc_type:   exception type to be used in error message
                     type name can be accesses as class variable
                     'exc_type_name'
 
         exc_value:  exception value to be used in error message
                     can be accesses as class variable 'exc_value'
 
         file:       name of file being compiled to be used in error message
                     can be accesses as class variable 'file'
 
         msg:        string message to be written as error message
-                    If no value is given, a default exception message will be given,
-                    consistent with 'standard' py_compile output.
-                    message (or default) can be accesses as class variable 'msg'
+                    If no value is given, a default exception message will be
+                    given, consistent with 'standard' py_compile output.
+                    message (or default) can be accesses as class variable
+                    'msg'
 
     """
 
     def __init__(self, exc_type, exc_value, file, msg=''):
         exc_type_name = exc_type.__name__
         if exc_type is SyntaxError:
-            tbtext = ''.join(traceback.format_exception_only(exc_type, exc_value))
+            tbtext = ''.join(traceback.format_exception_only(
+                exc_type, exc_value))
             errmsg = tbtext.replace('File "<string>"', 'File "%s"' % file)
         else:
             errmsg = "Sorry: %s: %s" % (exc_type_name,exc_value)
 
         Exception.__init__(self,msg or errmsg,exc_type_name,exc_value,file)
 
         self.exc_type_name = exc_type_name
         self.exc_value = exc_value
         self.file = file
         self.msg = msg or errmsg
 
     def __str__(self):
         return self.msg
 
 
 def wr_long(f, x):
     """Internal; write a 32-bit int to a file in little-endian order."""
-    f.write(bytes([x        & 0xff,
+    f.write(bytes([x         & 0xff,
                    (x >> 8)  & 0xff,
                    (x >> 16) & 0xff,
                    (x >> 24) & 0xff]))
 
 def compile(file, cfile=None, dfile=None, doraise=False):
     """Byte-compile one Python source file to Python bytecode.
 
-    Arguments:
-
-    file:    source filename
-    cfile:   target filename; defaults to source with 'c' or 'o' appended
-             ('c' normally, 'o' in optimizing mode, giving .pyc or .pyo)
-    dfile:   purported filename; defaults to source (this is the filename
-             that will show up in error messages)
-    doraise: flag indicating whether or not an exception should be
-             raised when a compile error is found. If an exception
-             occurs and this flag is set to False, a string
-             indicating the nature of the exception will be printed,
-             and the function will return to the caller. If an
-             exception occurs and this flag is set to True, a
-             PyCompileError exception will be raised.
+    :param file: The source file name.

[Benjamin, 2010/04/07 02:50:04]

Doc/library/py_compile.rst should be updated, too.

[barry, 2010/04/08 12:53:47]

I've been putting off updating the docs, but in this case I've made the change.

+    :param cfile: The target byte compiled file name.  When not given, this
+        defaults to the PEP 3147 location.
+    :param dfile: Purported file name, i.e. the file name that shows up in
+        error messages.  Defaults to the source file name.
+    :param doraise: Flag indicating whether or not an exception should be
+        raised when a compile error is found.  If an exception occurs and this
+        flag is set to False, a string indicating the nature of the exception
+        will be printed, and the function will return to the caller. If an
+        exception occurs and this flag is set to True, a PyCompileError
+        exception will be raised.
+    :return: Path to the resulting byte compiled file.
 
     Note that it isn't necessary to byte-compile Python modules for
     execution efficiency -- Python itself byte-compiles a module when
     it is loaded, and if it can, writes out the bytecode to the
     corresponding .pyc (or .pyo) file.
 
     However, if a Python installation is shared between users, it is a
     good idea to byte-compile all modules upon installation, since
     other users may not be able to write in the source directories,
     and thus they won't be able to write the .pyc/.pyo file, and then
     they would be byte-compiling every module each time it is loaded.
     This can slow down program start-up considerably.
 
     See compileall.py for a script/module that uses this module to
     byte-compile all installed files (or all files in selected
     directories).
-
     """
     with open(file, "rb") as f:
         encoding = tokenize.detect_encoding(f.readline)[0]
     with open(file, encoding=encoding) as f:
         try:
             timestamp = int(os.fstat(f.fileno()).st_mtime)
         except AttributeError:
             timestamp = int(os.stat(file).st_mtime)
         codestring = f.read()
     try:
         codeobject = builtins.compile(codestring, dfile or file,'exec')
     except Exception as err:
         py_exc = PyCompileError(err.__class__, err, dfile or file)
         if doraise:
             raise py_exc
         else:
             sys.stderr.write(py_exc.msg + '\n')
             return
     if cfile is None:
-        cfile = file + (__debug__ and 'c' or 'o')
+        cfile = cache_from_source(file)
+        try:
+            os.mkdir(os.path.dirname(cfile))
+        except OSError as error:
+            if error.errno != errno.EEXIST:
+                raise
     with open(cfile, 'wb') as fc:
         fc.write(b'\0\0\0\0')
         wr_long(fc, timestamp)
         marshal.dump(codeobject, fc)
         fc.flush()
         fc.seek(0, 0)
         fc.write(MAGIC)
+    return cfile
 
 def main(args=None):
     """Compile several source files.
 
     The files named in 'args' (or on the command line, if 'args' is
     not specified) are compiled and the resulting bytecode is cached
     in the normal manner.  This function does not search a directory
     structure to locate source files; it only compiles files named
     explicitly.  If '-' is the only parameter in args, the list of
     files is taken from standard input.
@@ skipping 21 matching lines @@
             try:
                 compile(filename, doraise=True)
             except PyCompileError as err:
                 # return value to indicate at least one failure
                 rv = 1
                 sys.stderr.write(error.msg)
     return rv
 
 if __name__ == "__main__":
     sys.exit(main())