Lib/py_compile.py

   1 """Routine to "compile" a .py file to a .pyc (or .pyo) file.
   2
   3 This module has intimate knowledge of the format of .pyc files.
   4 """
   5
   6 import imp
   7 MAGIC = imp.get_magic()
   8
   9 __all__ = ["compile"]
  10
  11 def wr_long(f, x):
  12     """Internal; write a 32-bit int to a file in little-endian order."""
  13     f.write(chr( x        & 0xff))
  14     f.write(chr((x >> 8)  & 0xff))
  15     f.write(chr((x >> 16) & 0xff))
  16     f.write(chr((x >> 24) & 0xff))
  17
  18 def compile(file, cfile=None, dfile=None):
  19     """Byte-compile one Python source file to Python bytecode.
  20
  21     Arguments:
  22
  23     file:  source filename
  24     cfile: target filename; defaults to source with 'c' or 'o' appended
  25            ('c' normally, 'o' in optimizing mode, giving .pyc or .pyo)
  26     dfile: purported filename; defaults to source (this is the filename
  27            that will show up in error messages)
  28
  29     Note that it isn't necessary to byte-compile Python modules for
  30     execution efficiency -- Python itself byte-compiles a module when
  31     it is loaded, and if it can, writes out the bytecode to the
  32     corresponding .pyc (or .pyo) file.
  33
  34     However, if a Python installation is shared between users, it is a
  35     good idea to byte-compile all modules upon installation, since
  36     other users may not be able to write in the source directories,
  37     and thus they won't be able to write the .pyc/.pyo file, and then
  38     they would be byte-compiling every module each time it is loaded.
  39     This can slow down program start-up considerably.
  40
  41     See compileall.py for a script/module that uses this module to
  42     byte-compile all installed files (or all files in selected
  43     directories).
  44
  45     """
  46     import os, marshal, __builtin__
  47     f = open(file)
  48     try:
  49         timestamp = long(os.fstat(f.fileno())[8])
  50     except AttributeError:
  51         timestamp = long(os.stat(file)[8])
  52     codestring = f.read()
  53     # If parsing from a string, line breaks are \n (see parsetok.c:tok_nextc)
  54     # Replace will return original string if pattern is not found, so
  55     # we don't need to check whether it is found first.
  56     codestring = codestring.replace("\r\n","\n")
  57     codestring = codestring.replace("\r","\n")
  58     f.close()
  59     if codestring and codestring[-1] != '\n':
  60         codestring = codestring + '\n'
  61     try:
  62         codeobject = __builtin__.compile(codestring, dfile or file, 'exec')
  63     except SyntaxError, detail:
  64         import traceback, sys
  65         lines = traceback.format_exception_only(SyntaxError, detail)
  66         for line in lines:
  67             sys.stderr.write(line.replace('File "<string>"',
  68                                             'File "%s"' % (dfile or file)))
  69         return
  70     if not cfile:
  71         cfile = file + (__debug__ and 'c' or 'o')
  72     fc = open(cfile, 'wb')
  73     fc.write('\0\0\0\0')
  74     wr_long(fc, timestamp)
  75     marshal.dump(codeobject, fc)
  76     fc.flush()
  77     fc.seek(0, 0)
  78     fc.write(MAGIC)
  79     fc.close()
  80     if os.name == 'mac':
  81         import macfs
  82         macfs.FSSpec(cfile).SetCreatorType('Pyth', 'PYC ')