pyx/helper.py

   1 #!/usr/bin/env python
   2 #
   3 #
   4 # Copyright (C) 2002 Jörg Lehmann <joergl@users.sourceforge.net>
   5 # Copyright (C) 2002 André Wobst <wobsta@users.sourceforge.net>
   6 #
   7 # This file is part of PyX (http://pyx.sourceforge.net/).
   8 #
   9 # PyX is free software; you can redistribute it and/or modify
  10 # it under the terms of the GNU General Public License as published by
  11 # the Free Software Foundation; either version 2 of the License, or
  12 # (at your option) any later version.
  13 #
  14 # PyX is distributed in the hope that it will be useful,
  15 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 # GNU General Public License for more details.
  18 #
  19 # You should have received a copy of the GNU General Public License
  20 # along with PyX; if not, write to the Free Software
  21 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  22
  23
  24 class _nodefault: pass
  25
  26
  27 def _isstring(arg):
  28     "arg is string-like (cf. python cookbook 3.2)"
  29     try: arg + ''
  30     except: return None
  31     return 1
  32
  33
  34 def _isnumber(arg):
  35     "arg is number-like"
  36     try: arg + 0
  37     except: return None
  38     return 1
  39
  40
  41 def _isinteger(arg):
  42     "arg is integer-like"
  43     try:
  44         if type(arg + 0.0) is type(arg):
  45             return None
  46         return 1
  47     except: return None
  48
  49
  50 def _issequence(arg):
  51     """arg is sequence-like (e.g. has a len)
  52        a string is *not* considered to be a sequence"""
  53     if _isstring(arg): return None
  54     try: len(arg)
  55     except: return None
  56     return 1
  57
  58
  59 def _ensuresequence(arg):
  60     """return arg or (arg,) depending on the result of _issequence,
  61        None is converted to ()"""
  62     if _isstring(arg): return (arg,)
  63     if arg is None: return ()
  64     if _issequence(arg): return arg
  65     return (arg,)
  66
  67
  68 def _getitemno(arg, n):
  69     if _issequence(arg):
  70         try: return arg[n]
  71         except: return None
  72     else:
  73         return arg
  74
  75
  76 def _issequenceofsequences(arg):
  77     """check if arg has a sequence or None as it's first entry"""
  78     return _issequence(arg) and len(arg) and (_issequence(arg[0]) or arg[0] is None)
  79
  80
  81 def _getsequenceno(arg, n):
  82     """get sequence number n if arg is a sequence of sequences,
  83        otherwise it gets just arg"""
  84     if _issequenceofsequences(arg):
  85         try: return arg[n]
  86         except: return None
  87     else:
  88         return arg