py_compile.py revision 54f22ed30bab2e64909ba2d79205cb4b87c69db2 
1"""Routine to "compile" a .py file to a .pyc (or .pyo) file.
2
3This module has intimate knowledge of the format of .pyc files.
4"""
5
6import imp
7MAGIC = imp.get_magic()
8
9def 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
16def 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 ')
76