Lib/codehack.py

   1 # A subroutine for extracting a function name from a code object
   2 # (with cache)
   3
   4 import sys
   5 from stat import *
   6 import string
   7 import os
   8 import linecache
   9
  10 # Extract the function or class name from a code object.
  11 # This is a bit of a hack, since a code object doesn't contain
  12 # the name directly.  So what do we do:
  13 # - get the filename (which *is* in the code object)
  14 # - look in the code string to find the first SET_LINENO instruction
  15 #   (this must be the first instruction)
  16 # - get the line from the file
  17 # - if the line starts with 'class' or 'def' (after possible whitespace),
  18 #   extract the following identifier
  19 #
  20 # This breaks apart when the function was read from <stdin>
  21 # or constructed by exec(), when the file is not accessible,
  22 # and also when the file has been modified or when a line is
  23 # continued with a backslash before the function or class name.
  24 #
  25 # Because this is a pretty expensive hack, a cache is kept.
  26
  27 SET_LINENO = 127 # The opcode (see "opcode.h" in the Python source)
  28 identchars = string.letters + string.digits + '_' # Identifier characters
  29
  30 _namecache = {} # The cache
  31
  32 def getcodename(co):
  33         key = `co` # arbitrary but uniquely identifying string
  34         if _namecache.has_key(key): return _namecache[key]
  35         filename = co.co_filename
  36         code = co.co_code
  37         name = ''
  38         if ord(code[0]) == SET_LINENO:
  39                 lineno = ord(code[1]) | ord(code[2]) << 8
  40                 line = linecache.getline(filename, lineno)
  41                 words = string.split(line)
  42                 if len(words) >= 2 and words[0] in ('def', 'class'):
  43                         name = words[1]
  44                         for i in range(len(name)):
  45                                 if name[i] not in identchars:
  46                                         name = name[:i]
  47                                         break
  48         _namecache[key] = name
  49         return name
  50
  51 # Use the above routine to find a function's name.
  52
  53 def getfuncname(func):
  54         return getcodename(func.func_code)
  55
  56 # A part of the above code to extract just the line number from a code object.
  57
  58 def getlineno(co):
  59         code = co.co_code
  60         if ord(code[0]) == SET_LINENO:
  61                 return ord(code[1]) | ord(code[2]) << 8
  62         else:
  63                 return -1