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 import base
  25
  26
  27 class nodefault: pass
  28
  29
  30 def isstring(arg):
  31     "arg is string-like (cf. python cookbook 3.2)"
  32     try: arg + ''
  33     except: return 0
  34     return 1
  35
  36
  37 def isnumber(arg):
  38     "arg is number-like"
  39     try: arg + 0
  40     except: return 0
  41     return 1
  42
  43
  44 def isinteger(arg):
  45     "arg is integer-like"
  46     try:
  47         if type(arg + 0.0) is type(arg):
  48             return 0
  49         return 1
  50     except: return 0
  51
  52
  53 def issequence(arg):
  54     """arg is sequence-like (e.g. has a len)
  55        a string is *not* considered to be a sequence"""
  56     if isstring(arg): return 0
  57     try: len(arg)
  58     except: return 0
  59     return 1
  60
  61
  62 def ensuresequence(arg):
  63     """return arg or (arg,) depending on the result of issequence,
  64        None is converted to ()"""
  65     if isstring(arg): return (arg,)
  66     if arg is None: return ()
  67     if issequence(arg): return arg
  68     return (arg,)
  69
  70 def ensurelist(arg):
  71     """return list(arg) or [arg] depending on the result of isequence,
  72        None is converted to []"""
  73     if isstring(arg): return [arg]
  74     if arg is None: return []
  75     if issequence(arg): return list(arg)
  76     return [arg]
  77
  78 def getitemno(arg, n):
  79     if issequence(arg):
  80         try: return arg[n]
  81         except: return None
  82     else:
  83         return arg
  84
  85
  86 def issequenceofsequences(arg):
  87     """check if arg has a sequence or None as it's first entry"""
  88     return issequence(arg) and len(arg) and (issequence(arg[0]) or arg[0] is None)
  89
  90
  91 def getsequenceno(arg, n):
  92     """get sequence number n if arg is a sequence of sequences,
  93        otherwise it gets just arg"""
  94     if issequenceofsequences(arg):
  95         try: return arg[n]
  96         except: return None
  97     else:
  98         return arg
  99
 100
 101
 102 class AttrError(base.PyXExcept): pass
 103
 104
 105 def checkattr(attrs, allowonce=(), allowmulti=()):
 106     """checks the sequence attrs for occurencies of instances
 107        the classes provided as a tuple to allowonce are allowed only once
 108        the classes provided as a tuple to allowonce are allowed multiple times"""
 109     hadonce = []
 110     for attr in attrs:
 111         for once in allowonce:
 112             if isinstance(attr, once):
 113                 if once in hadonce:
 114                     raise AttrError("only a single instance of %r allowed" % once)
 115                 else:
 116                     hadonce += [once]
 117                     break
 118         else:
 119             for multi in allowmulti:
 120                 if isinstance(attr, multi):
 121                     break
 122             else:
 123                 raise AttrError("%r not allowed" % attr)
 124
 125 def getattrs(attrs, get, default=nodefault):
 126     """creates a list of instances of class get out of the sequence attrs
 127        when no instances are found it returns default when set (whatever it is)
 128        when no instances are found it raises AttrError when default is not set"""
 129     first = 1
 130     for attr in attrs:
 131         if isinstance(attr, get):
 132             if first:
 133                 result = [attr]
 134                 first = 0
 135             else:
 136                 result.append(attr)
 137     if first:
 138         if default is nodefault:
 139             raise AttrError
 140         else:
 141             return default
 142     return result
 143
 144 def countattrs(attrs, check):
 145     "count the occurancies of instances of class get out of the sequence attrs"
 146     return len(getattrs(attrs, check, ()))
 147
 148 def getattr(attrs, get, default=nodefault):
 149     """get the instance of class get out of the sequence attrs
 150        when no instance is found it returns default when set (whatever it is)
 151        when no instance is found it raises AttrError when default is not set
 152        when no multiple instances are found it always raises AttrError"""
 153     try:
 154         result = getattrs(attrs, get)
 155     except AttrError:
 156         if default is nodefault:
 157             raise AttrError
 158         else:
 159             return default
 160     if len(result) > 1:
 161         raise AttrError
 162     return result[0]
 163
 164 def getfirstattr(attrs, get, default=nodefault):
 165     """get the first instance of class get out of the sequence attrs
 166        when no instances are found it returns default when set (whatever it is)
 167        when no instances are found it raises AttrError when default is not set"""
 168     try:
 169         result = getattrs(attrs, get)
 170     except AttrError:
 171         if default is nodefault:
 172             raise AttrError
 173         else:
 174             return default
 175     return result[0]
 176
 177 def getlastattr(attrs, get, default=nodefault):
 178     """get the last instance of class get out of the sequence attrs
 179        when no instances are found it returns default when set (whatever it is)
 180        when no instances are found it raises AttrError when default is not set"""
 181     try:
 182         result = getattrs(attrs, get)
 183     except AttrError:
 184         if default is nodefault:
 185             raise AttrError
 186         else:
 187             return default
 188     return result[-1]
 189
 190 def delattr(attrs, remove):
 191     """create a new list of instances out of the sequence attrs
 192        where all instances of class remove are removed"""
 193     result = []
 194     for attr in attrs:
 195         if not isinstance(attr, remove):
 196             result.append(attr)
 197     return result
 198
 199
 200 if __name__=="__main__":
 201     class a: pass
 202     class b: pass
 203     class c(b): pass
 204     class A: pass
 205     class B: pass
 206     class C(B): pass
 207     checkattr((a(), A(), A()), (a, b), (A, B))
 208     checkattr((c(), A(), A()), (a, b), (A, B))
 209     try:
 210         checkattr((a(), A(), A(), a()), (a, b), (A, B))
 211         print "error"
 212     except AttrError: pass
 213     try:
 214         checkattr((c(), A(), A(), c()), (a, b), (A, B))
 215         print "error"
 216     except AttrError: pass
 217     x1, x2 = a(), a()
 218     if getattrs((x1, A(), A()), a) != [x1]:
 219         print "error"
 220     if getattrs((x1, A(), A(), x2), a) != [x1, x2]:
 221         print "error"
 222     if getattr((x1, A(), A()), a) != x1:
 223         print "error"
 224     try:
 225         getattr((x1, A(), A(), x2), a)
 226         print "error"
 227     except AttrError: pass
 228     if getfirstattr((x1, A(), A(), x2), a) != x1:
 229         print "error"
 230     if getlastattr((x1, A(), A(), x2), a) != x2:
 231         print "error"
 232     if getattr((x1, A(), A()), a, x2) != x1:
 233         print "error"
 234     if getattr((A(), A()), a, x2) != x2:
 235         print "error"
 236