Add comments to NamedTuple code.
Let the field spec be either a string or a non-string sequence (suggested by Martin Blais with use cases).
Improve the error message in the case of a SyntaxError (caused by a duplicate field name).
diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index fc5bbeb..5da7b60 100644
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -363,9 +363,11 @@
helpful docstring (with typename and fieldnames) and a helpful :meth:`__repr__`
method which lists the tuple contents in a ``name=value`` format.
- The *fieldnames* are specified in a single string with each fieldname separated by
- a space and/or comma. Any valid Python identifier may be used for a fieldname
- except for names starting and ending with double underscores.
+ The *fieldnames* are a single string with each fieldname separated by a space
+ and/or comma (for example "x y" or "x, y"). Alternately, the *fieldnames*
+ can be specified as list or tuple of strings. Any valid Python identifier
+ may be used for a fieldname except for names starting and ending with double
+ underscores.
If *verbose* is true, will print the class definition.
diff --git a/Lib/collections.py b/Lib/collections.py
index 7b10712..c5eb79c 100644
--- a/Lib/collections.py
+++ b/Lib/collections.py
@@ -4,7 +4,7 @@
from operator import itemgetter as _itemgetter
import sys as _sys
-def NamedTuple(typename, s, verbose=False):
+def NamedTuple(typename, field_names, verbose=False):
"""Returns a new subclass of tuple with named fields.
>>> Point = NamedTuple('Point', 'x y')
@@ -28,11 +28,16 @@
"""
- field_names = tuple(s.replace(',', ' ').split()) # names separated by spaces and/or commas
+ # Parse and validate the field names
+ if isinstance(field_names, basestring):
+ field_names = s.replace(',', ' ').split() # names separated by spaces and/or commas
+ field_names = tuple(field_names)
if not ''.join((typename,) + field_names).replace('_', '').isalnum():
raise ValueError('Type names and field names can only contain alphanumeric characters and underscores')
if any(name.startswith('__') and name.endswith('__') for name in field_names):
raise ValueError('Field names cannot start and end with double underscores')
+
+ # Create and fill-in the class template
argtxt = repr(field_names).replace("'", "")[1:-1] # tuple repr without parens or quotes
reprtxt = ', '.join('%s=%%r' % name for name in field_names)
template = '''class %(typename)s(tuple):
@@ -53,11 +58,21 @@
template += ' %s = property(itemgetter(%d))\n' % (name, i)
if verbose:
print template
+
+ # Execute the template string in a temporary namespace
m = dict(itemgetter=_itemgetter)
- exec template in m
+ try:
+ exec template in m
+ except SyntaxError, e:
+ raise SyntaxError(e.message + ':\n' + template)
result = m[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['__name__']
+
return result
diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index 939c3ce..c260bc7 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -40,6 +40,11 @@
p = Point(x=11, y=22)
self.assertEqual(repr(p), 'Point(x=11, y=22)')
+ # verify that fieldspec can be a non-string sequence
+ Point = NamedTuple('Point', ('x', 'y'))
+ p = Point(x=11, y=22)
+ self.assertEqual(repr(p), 'Point(x=11, y=22)')
+
def test_tupleness(self):
Point = NamedTuple('Point', 'x y')
p = Point(11, 22)