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