pokedex/compatibility.py

   1 """Things missing from older versions of Python
   2
   3 Currently these are functions missing from Python 2.5.
   4 """
   5
   6 try:
   7     from itertools import permutations
   8 except ImportError:
   9     # From the itertools documentation
  10     def permutations(iterable, r=None):
  11         # permutations('ABCD', 2) --> AB AC AD BA BC BD CA CB CD DA DB DC
  12         # permutations(range(3)) --> 012 021 102 120 201 210
  13         pool = tuple(iterable)
  14         n = len(pool)
  15         r = n if r is None else r
  16         if r > n:
  17             return
  18         indices = range(n)
  19         cycles = range(n, n-r, -1)
  20         yield tuple(pool[i] for i in indices[:r])
  21         while n:
  22             for i in reversed(range(r)):
  23                 cycles[i] -= 1
  24                 if cycles[i] == 0:
  25                     indices[i:] = indices[i+1:] + indices[i:i+1]
  26                     cycles[i] = n - i
  27                 else:
  28                     j = cycles[i]
  29                     indices[i], indices[-j] = indices[-j], indices[i]
  30                     yield tuple(pool[i] for i in indices[:r])
  31                     break
  32             else:
  33                 return
  34
  35 try:
  36     from collections import namedtuple
  37 except ImportError:
  38     # http://code.activestate.com/recipes/500261-named-tuples/
  39     from operator import itemgetter as _itemgetter
  40     from keyword import iskeyword as _iskeyword
  41     import sys as _sys
  42
  43     def namedtuple(typename, field_names, verbose=False, rename=False):
  44         """Returns a new subclass of tuple with named fields.
  45
  46         >>> Point = namedtuple('Point', 'x y')
  47         >>> Point.__doc__                   # docstring for the new class
  48         'Point(x, y)'
  49         >>> p = Point(11, y=22)             # instantiate with positional args or keywords
  50         >>> p[0] + p[1]                     # indexable like a plain tuple
  51         33
  52         >>> x, y = p                        # unpack like a regular tuple
  53         >>> x, y
  54         (11, 22)
  55         >>> p.x + p.y                       # fields also accessable by name
  56         33
  57         >>> d = p._asdict()                 # convert to a dictionary
  58         >>> d['x']
  59         11
  60         >>> Point(**d)                      # convert from a dictionary
  61         Point(x=11, y=22)
  62         >>> p._replace(x=100)               # _replace() is like str.replace() but targets named fields
  63         Point(x=100, y=22)
  64
  65         """
  66
  67         # Parse and validate the field names.  Validation serves two purposes,
  68         # generating informative error messages and preventing template injection attacks.
  69         if isinstance(field_names, basestring):
  70             field_names = field_names.replace(',', ' ').split() # names separated by whitespace and/or commas
  71         field_names = tuple(map(str, field_names))
  72         if rename:
  73             names = list(field_names)
  74             seen = set()
  75             for i, name in enumerate(names):
  76                 if (not min(c.isalnum() or c=='_' for c in name) or _iskeyword(name)
  77                     or not name or name[0].isdigit() or name.startswith('_')
  78                     or name in seen):
  79                         names[i] = '_%d' % i
  80                 seen.add(name)
  81             field_names = tuple(names)
  82         for name in (typename,) + field_names:
  83             if not min(c.isalnum() or c=='_' for c in name):
  84                 raise ValueError('Type names and field names can only contain alphanumeric characters and underscores: %r' % name)
  85             if _iskeyword(name):
  86                 raise ValueError('Type names and field names cannot be a keyword: %r' % name)
  87             if name[0].isdigit():
  88                 raise ValueError('Type names and field names cannot start with a number: %r' % name)
  89         seen_names = set()
  90         for name in field_names:
  91             if name.startswith('_') and not rename:
  92                 raise ValueError('Field names cannot start with an underscore: %r' % name)
  93             if name in seen_names:
  94                 raise ValueError('Encountered duplicate field name: %r' % name)
  95             seen_names.add(name)
  96
  97         # Create and fill-in the class template
  98         numfields = len(field_names)
  99         argtxt = repr(field_names).replace("'", "")[1:-1]   # tuple repr without parens or quotes
 100         reprtxt = ', '.join('%s=%%r' % name for name in field_names)
 101         template = '''class %(typename)s(tuple):
 102             '%(typename)s(%(argtxt)s)' \n
 103             __slots__ = () \n
 104             _fields = %(field_names)r \n
 105             def __new__(_cls, %(argtxt)s):
 106                 return _tuple.__new__(_cls, (%(argtxt)s)) \n
 107             @classmethod
 108             def _make(cls, iterable, new=tuple.__new__, len=len):
 109                 'Make a new %(typename)s object from a sequence or iterable'
 110                 result = new(cls, iterable)
 111                 if len(result) != %(numfields)d:
 112                     raise TypeError('Expected %(numfields)d arguments, got %%d' %% len(result))
 113                 return result \n
 114             def __repr__(self):
 115                 return '%(typename)s(%(reprtxt)s)' %% self \n
 116             def _asdict(self):
 117                 'Return a new dict which maps field names to their values'
 118                 return dict(zip(self._fields, self)) \n
 119             def _replace(_self, **kwds):
 120                 'Return a new %(typename)s object replacing specified fields with new values'
 121                 result = _self._make(map(kwds.pop, %(field_names)r, _self))
 122                 if kwds:
 123                     raise ValueError('Got unexpected field names: %%r' %% kwds.keys())
 124                 return result \n
 125             def __getnewargs__(self):
 126                 return tuple(self) \n\n''' % locals()
 127         for i, name in enumerate(field_names):
 128             template += '            %s = _property(_itemgetter(%d))\n' % (name, i)
 129         if verbose:
 130             print template
 131
 132         # Execute the template string in a temporary namespace
 133         namespace = dict(_itemgetter=_itemgetter, __name__='namedtuple_%s' % typename,
 134                          _property=property, _tuple=tuple)
 135         try:
 136             exec template in namespace
 137         except SyntaxError, e:
 138             raise SyntaxError(e.message + ':\n' + template)
 139         result = namespace[typename]
 140
 141         # For pickling to work, the __module__ variable needs to be set to the frame
 142         # where the named tuple is created.  Bypass this step in enviroments where
 143         # sys._getframe is not defined (Jython for example) or sys._getframe is not
 144         # defined for arguments greater than 0 (IronPython).
 145         try:
 146             result.__module__ = _sys._getframe(1).f_globals.get('__name__', '__main__')
 147         except (AttributeError, ValueError):
 148             pass
 149
 150         return result