Sync-up named tuples with the latest version of the ASPN recipe.
Allows optional commas in the field-name spec (help when named tuples are used in conjuction with sql queries).
Adds the __fields__ attribute for introspection and to support conversion to dictionary form.
Adds a __replace__() method similar to str.replace() but using a named field as a target.
Clean-up spelling and presentation in doc-strings.
diff --git a/Lib/collections.py b/Lib/collections.py
index 4a860dd..c2b1176 100644
--- a/Lib/collections.py
+++ b/Lib/collections.py
@@ -8,33 +8,42 @@
"""Returns a new subclass of tuple with named fields.
>>> Point = NamedTuple('Point', 'x y')
- >>> Point.__doc__ # docstring for the new class
+ >>> 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] # works just like the tuple (11, 22)
+ >>> p = Point(11, y=22) # instantiate with positional args or keywords
+ >>> p[0] + p[1] # works just like the tuple (11, 22)
33
- >>> x, y = p # unpacks just like a tuple
+ >>> x, y = p # unpacks just like a tuple
>>> x, y
(11, 22)
- >>> p.x + p.y # fields also accessable by name
+ >>> p.x + p.y # fields also accessable by name
33
- >>> p # readable __repr__ with name=value style
+ >>> p # readable __repr__ with name=value style
Point(x=11, y=22)
+ >>> p.__replace__('x', 100) # __replace__() is like str.replace() but targets a named field
+ Point(x=100, y=22)
+ >>> d = dict(zip(p.__fields__, p)) # use __fields__ to make a dictionary
+ >>> d['x']
+ 11
"""
- field_names = s.split()
- if not ''.join([typename] + field_names).replace('_', '').isalnum():
+ field_names = tuple(s.replace(',', ' ').split()) # names separated by spaces and/or commas
+ if not ''.join((typename,) + field_names).replace('_', '').isalnum():
raise ValueError('Type names and field names can only contain alphanumeric characters and underscores')
argtxt = ', '.join(field_names)
reprtxt = ', '.join('%s=%%r' % name for name in field_names)
template = '''class %(typename)s(tuple):
'%(typename)s(%(argtxt)s)'
__slots__ = ()
+ __fields__ = %(field_names)r
def __new__(cls, %(argtxt)s):
return tuple.__new__(cls, (%(argtxt)s,))
def __repr__(self):
return '%(typename)s(%(reprtxt)s)' %% self
+ def __replace__(self, field, value):
+ 'Return a new %(typename)s object replacing one field with a new value'
+ return %(typename)s(**dict(zip(%(field_names)r, self) + [(field, value)]))
''' % locals()
for i, name in enumerate(field_names):
template += '\n %s = property(itemgetter(%d))\n' % (name, i)
@@ -51,9 +60,9 @@
if __name__ == '__main__':
- # verify that instances are pickable
+ # verify that instances can be pickled
from cPickle import loads, dumps
- Point = NamedTuple('Point', 'x y')
+ Point = NamedTuple('Point', 'x, y')
p = Point(x=10, y=20)
assert p == loads(dumps(p))