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Handle corner cased on 0-tuples and 1-tuples. Add verbose option so people can see how it works.

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This commit is contained in:
Raymond Hettinger 2007-09-18 03:33:19 +00:00
parent de37a8cec7
commit 2b03d45bb9
3 changed files with 33 additions and 9 deletions
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17
Lib/collections.py
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@ -4,7 +4,7 @@ from _collections import deque, defaultdict
from operator import itemgetter as _itemgetter
import sys as _sys
def NamedTuple(typename, s):
def NamedTuple(typename, s, verbose=False):
"""Returns a new subclass of tuple with named fields.
>>> Point = NamedTuple('Point', 'x y')
@ -28,25 +28,26 @@ def NamedTuple(typename, s):
"""
field_names = tuple(s.replace(',', ' ').split()) # names separated by spaces and/or commas
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)
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):
'%(typename)s(%(argtxt)s)'
__slots__ = ()
__fields__ = %(field_names)r
def __new__(cls, %(argtxt)s):
return tuple.__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()
return %(typename)s(**dict(zip(%(field_names)r, self) + [(field, value)])) \n''' % locals()
for i, name in enumerate(field_names):
template += '\n %s = property(itemgetter(%d))\n' % (name, i)
template += ' %s = property(itemgetter(%d))\n' % (name, i)
if verbose:
print template
m = dict(itemgetter=_itemgetter)
exec template in m
result = m[typename]
@ -62,7 +63,7 @@ def NamedTuple(typename, s):
if __name__ == '__main__':
# verify that instances can be pickled
from cPickle import loads, dumps
Point = NamedTuple('Point', 'x, y')
Point = NamedTuple('Point', 'x, y', True)
p = Point(x=10, y=20)
assert p == loads(dumps(p))