60aa5581c1
Download source: https://pythonfutures.googlecode.com/archive/05e0c9c1b3d493f0c7e5833723a1ea99d024bad4.zip
102 lines
4.5 KiB
Python
Executable File
102 lines
4.5 KiB
Python
Executable File
from keyword import iskeyword as _iskeyword
|
|
from operator import itemgetter as _itemgetter
|
|
import sys as _sys
|
|
|
|
|
|
def namedtuple(typename, field_names):
|
|
"""Returns a new subclass of tuple with named fields.
|
|
|
|
>>> 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)
|
|
|
|
# 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, namespace)
|
|
except SyntaxError:
|
|
e = _sys.exc_info()[1]
|
|
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
|