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from __future__ import absolute_import, print_function, division
import operator
from functools import partial
from petl.compat import text_type, binary_type, numeric_types
class Comparable(object):
"""Wrapper class to allow for flexible comparison of objects of different
types, preserving the relaxed sorting behaviour of Python 2 with
additional flexibility to allow for comparison of arbitrary objects with
the `None` value (for example, the date and time objects from the standard
library cannot be directly compared with `None` in Python 2).
"""
__slots__ = ['obj', 'inner']
def __init__(self, obj):
# store wrapped object unchanged
self.inner = obj
# handle lists and tuples
if isinstance(obj, (list, tuple)):
obj = tuple(Comparable(o) for o in obj)
self.obj = obj
def __lt__(self, other):
# convenience
obj = self.obj
if isinstance(other, Comparable):
other = other.obj
# None < everything else
if other is None:
return False
if obj is None:
return True
# numbers < everything else (except None)
if isinstance(obj, numeric_types) \
and not isinstance(other, numeric_types):
return True
if not isinstance(obj, numeric_types) \
and isinstance(other, numeric_types):
return False
# binary < unicode
if isinstance(obj, text_type) and isinstance(other, binary_type):
return False
if isinstance(obj, binary_type) and isinstance(other, text_type):
return True
try:
# attempt native comparison
return obj < other
except TypeError:
# fall back to comparing type names
return _typestr(obj) < _typestr(other)
def __eq__(self, other):
if isinstance(other, Comparable):
return self.obj == other.obj
return self.obj == other
def __le__(self, other):
return self < other or self == other
def __gt__(self, other):
return not (self < other or self == other)
def __ge__(self, other):
return not (self < other)
def __str__(self):
return str(self.obj)
def __unicode__(self):
return text_type(self.obj)
def __repr__(self):
return 'Comparable(' + repr(self.obj) + ')'
def __iter__(self, *args, **kwargs):
return iter(self.obj, *args, **kwargs)
def __len__(self):
return len(self.obj)
def __getitem__(self, item):
return self.obj.__getitem__(item)
def _typestr(x):
# attempt to preserve Python 2 name orderings
if isinstance(x, binary_type):
return 'str'
if isinstance(x, text_type):
return 'unicode'
return type(x).__name__
def comparable_itemgetter(*args):
getter = operator.itemgetter(*args)
getter_with_default = _itemgetter_with_default(*args)
def _getter_with_fallback(obj):
try:
return getter(obj)
except (IndexError, KeyError):
return getter_with_default(obj)
g = lambda x: Comparable(_getter_with_fallback(x))
return g
def _itemgetter_with_default(*args):
""" itemgetter compatible with `operator.itemgetter` behavior, filling missing
values with default instead of raising IndexError or KeyError """
def _get_default(obj, item, default):
try:
return obj[item]
except (IndexError, KeyError):
return default
if len(args) == 1:
return partial(_get_default, item=args[0], default=None)
return lambda obj: tuple(_get_default(obj, item=item, default=None) for item in args)
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