From: W. Trevor King <wking@drexel.edu>
Date: Wed, 20 Oct 2010 23:09:40 +0000 (-0400)
Subject: Work around namedtuple import for Pythons < 2.6.
X-Git-Url: http://git.tremily.us/?p=sawsim.git;a=commitdiff_plain;h=e10ee023837fa0d389b68bd8d1b2b545fdfb71ac

Work around namedtuple import for Pythons < 2.6.
---

diff --git a/pysawsim/sawsim.py b/pysawsim/sawsim.py
index 00dea1a..a58deab 100644
--- a/pysawsim/sawsim.py
+++ b/pysawsim/sawsim.py
@@ -24,9 +24,111 @@
 * `parse()` parses the output of a typical `sawsim` run.
 """
 
+try:
+    from collections import namedtuple
+except ImportError:  # work around Python < 2.6
+    from operator import itemgetter as _itemgetter
+    from keyword import iskeyword as _iskeyword
+    import sys as _sys
+    def namedtuple(typename, field_names, verbose=False):
+        """Returns a new subclass of tuple with named fields.
 
-from collections import namedtuple
+        Copied from Python 2.6's collections.py.
 
+        >>> Point = namedtuple('Point', 'x y')
+        >>> Point.__doc__                   # docstring for the new class
+        'Point(x, y)'
+        >>> p = Point(11, y=22)             # instantiate with positional args or keywords
+        >>> p[0] + p[1]                     # indexable like a plain tuple
+        33
+        >>> x, y = p                        # unpack like a regular tuple
+        >>> x, y
+        (11, 22)
+        >>> p.x + p.y                       # fields also accessable by name
+        33
+        >>> d = p._asdict()                 # convert to a dictionary
+        >>> d['x']
+        11
+        >>> Point(**d)                      # convert from a dictionary
+        Point(x=11, y=22)
+        >>> p._replace(x=100)               # _replace() is like str.replace() but targets named fields
+        Point(x=100, y=22)
+
+        """
+
+        # Parse and validate the field names.  Validation serves two purposes,
+        # generating informative error messages and preventing template injection attacks.
+        if isinstance(field_names, basestring):
+            field_names = field_names.replace(',', ' ').split() # names separated by whitespace and/or commas
+        field_names = tuple(map(str, field_names))
+        for name in (typename,) + field_names:
+            if not all(c.isalnum() or c=='_' for c in name):
+                raise ValueError('Type names and field names can only contain alphanumeric characters and underscores: %r' % name)
+            if _iskeyword(name):
+                raise ValueError('Type names and field names cannot be a keyword: %r' % name)
+            if name[0].isdigit():
+                raise ValueError('Type names and field names cannot start with a number: %r' % name)
+        seen_names = set()
+        for name in field_names:
+            if name.startswith('_'):
+                raise ValueError('Field names cannot start with an underscore: %r' % name)
+            if name in seen_names:
+                raise ValueError('Encountered duplicate field name: %r' % name)
+            seen_names.add(name)
+
+        # Create and fill-in the class template
+        numfields = len(field_names)
+        argtxt = repr(field_names).replace("'", "")[1:-1]   # tuple repr without parens or quotes
+        reprtxt = ', '.join('%s=%%r' % name for name in field_names)
+        dicttxt = ', '.join('%r: t[%d]' % (name, pos) for pos, name in enumerate(field_names))
+        template = '''class %(typename)s(tuple):
+        '%(typename)s(%(argtxt)s)' \n
+        __slots__ = () \n
+        _fields = %(field_names)r \n
+        def __new__(_cls, %(argtxt)s):
+            return _tuple.__new__(_cls, (%(argtxt)s)) \n
+        @classmethod
+        def _make(cls, iterable, new=tuple.__new__, len=len):
+            'Make a new %(typename)s object from a sequence or iterable'
+            result = new(cls, iterable)
+            if len(result) != %(numfields)d:
+                raise TypeError('Expected %(numfields)d arguments, got %%d' %% len(result))
+            return result \n
+        def __repr__(self):
+            return '%(typename)s(%(reprtxt)s)' %% self \n
+        def _asdict(t):
+            'Return a new dict which maps field names to their values'
+            return {%(dicttxt)s} \n
+        def _replace(_self, **kwds):
+            'Return a new %(typename)s object replacing specified fields with new values'
+            result = _self._make(map(kwds.pop, %(field_names)r, _self))
+            if kwds:
+                raise ValueError('Got unexpected field names: %%r' %% kwds.keys())
+            return result \n
+        def __getnewargs__(self):
+            return tuple(self) \n\n''' % locals()
+        for i, name in enumerate(field_names):
+            template += '        %s = _property(_itemgetter(%d))\n' % (name, i)
+        if verbose:
+            print template
+
+        # Execute the template string in a temporary namespace and
+        # support tracing utilities by setting a value for frame.f_globals['__name__']
+        namespace = dict(_itemgetter=_itemgetter, __name__='namedtuple_%s' % typename,
+                         _property=property, _tuple=tuple)
+        try:
+            exec template in namespace
+        except SyntaxError, e:
+            raise SyntaxError(e.message + ':\n' + template)
+        result = namespace[typename]
+
+        # For pickling to work, the __module__ variable needs to be set to the frame
+        # where the named tuple is created.  Bypass this step in enviroments where
+        # sys._getframe is not defined (Jython for example).
+        if hasattr(_sys, '_getframe'):
+            result.__module__ = _sys._getframe(1).f_globals.get('__name__', '__main__')
+
+        return result
 
 
 Event = namedtuple(