pyx/helper.py

   1 #!/usr/bin/env python
   2 # -*- coding: ISO-8859-1 -*-
   3 #
   4 #
   5 # Copyright (C) 2002-2004 Jörg Lehmann <joergl@users.sourceforge.net>
   6 # Copyright (C) 2002-2004 André Wobst <wobsta@users.sourceforge.net>
   7 #
   8 # This file is part of PyX (http://pyx.sourceforge.net/).
   9 #
  10 # PyX is free software; you can redistribute it and/or modify
  11 # it under the terms of the GNU General Public License as published by
  12 # the Free Software Foundation; either version 2 of the License, or
  13 # (at your option) any later version.
  14 #
  15 # PyX is distributed in the hope that it will be useful,
  16 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 # GNU General Public License for more details.
  19 #
  20 # You should have received a copy of the GNU General Public License
  21 # along with PyX; if not, write to the Free Software
  22 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  23
  24
  25 class nodefault: pass
  26
  27
  28 def isstring(arg):
  29     "arg is string-like (cf. python cookbook 3.2)"
  30     try: arg + ''
  31     except: return 0
  32     return 1
  33
  34
  35 def isnumber(arg):
  36     "arg is number-like"
  37     try: arg + 0
  38     except: return 0
  39     return 1
  40
  41
  42 def isinteger(arg):
  43     "arg is integer-like"
  44     try:
  45         if type(arg + 0.0) is type(arg):
  46             return 0
  47         return 1
  48     except: return 0
  49
  50
  51 def issequence(arg):
  52     """arg is sequence-like (e.g. has a len)
  53        a string is *not* considered to be a sequence"""
  54     if isstring(arg): return 0
  55     try: len(arg)
  56     except: return 0
  57     return 1
  58
  59
  60 def ensuresequence(arg):
  61     """return arg or (arg,) depending on the result of issequence,
  62        None is converted to ()"""
  63     if isstring(arg): return (arg,)
  64     if arg is None: return ()
  65     if issequence(arg): return arg
  66     return (arg,)
  67
  68
  69 def ensurelist(arg):
  70     """return list(arg) or [arg] depending on the result of isequence,
  71        None is converted to []"""
  72     if isstring(arg): return [arg]
  73     if arg is None: return []
  74     if issequence(arg): return list(arg)
  75     return [arg]
  76
  77 def getitemno(arg, n):
  78     """get item number n if arg is a sequence (when the sequence
  79        is not long enough, None is returned), otherweise arg is
  80        returned"""
  81     if issequence(arg):
  82         try: return arg[n]
  83         except: return None
  84     else:
  85         return arg
  86
  87
  88 def issequenceofsequences(arg):
  89     """check if arg has a sequence or None as it's first entry"""
  90     return issequence(arg) and len(arg) and (issequence(arg[0]) or arg[0] is None)
  91
  92
  93 def getsequenceno(arg, n):
  94     """get sequence number n if arg is a sequence of sequences (when
  95        the sequence is not long enough, None is returned), otherwise
  96        arg is returned"""
  97     if issequenceofsequences(arg):
  98         try: return arg[n]
  99         except: return None
 100     else:
 101         return arg