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from collections import defaultdict, deque
from itertools import filterfalse
def unique_everseen(iterable, key=None):
"List unique elements, preserving order. Remember all elements ever seen."
# unique_everseen('AAAABBBCCDAABBB') --> A B C D
# unique_everseen('ABBCcAD', str.lower) --> A B C D
seen = set()
seen_add = seen.add
if key is None:
for element in filterfalse(seen.__contains__, iterable):
seen_add(element)
yield element
else:
for element in iterable:
k = key(element)
if k not in seen:
seen_add(k)
yield element
# copied from more_itertools 8.8
def always_iterable(obj, base_type=(str, bytes)):
"""If *obj* is iterable, return an iterator over its items::
>>> obj = (1, 2, 3)
>>> list(always_iterable(obj))
[1, 2, 3]
If *obj* is not iterable, return a one-item iterable containing *obj*::
>>> obj = 1
>>> list(always_iterable(obj))
[1]
If *obj* is ``None``, return an empty iterable:
>>> obj = None
>>> list(always_iterable(None))
[]
By default, binary and text strings are not considered iterable::
>>> obj = 'foo'
>>> list(always_iterable(obj))
['foo']
If *base_type* is set, objects for which ``isinstance(obj, base_type)``
returns ``True`` won't be considered iterable.
>>> obj = {'a': 1}
>>> list(always_iterable(obj)) # Iterate over the dict's keys
['a']
>>> list(always_iterable(obj, base_type=dict)) # Treat dicts as a unit
[{'a': 1}]
Set *base_type* to ``None`` to avoid any special handling and treat objects
Python considers iterable as iterable:
>>> obj = 'foo'
>>> list(always_iterable(obj, base_type=None))
['f', 'o', 'o']
"""
if obj is None:
return iter(())
if (base_type is not None) and isinstance(obj, base_type):
return iter((obj,))
try:
return iter(obj)
except TypeError:
return iter((obj,))
# Copied from more_itertools 10.3
class bucket:
"""Wrap *iterable* and return an object that buckets the iterable into
child iterables based on a *key* function.
>>> iterable = ['a1', 'b1', 'c1', 'a2', 'b2', 'c2', 'b3']
>>> s = bucket(iterable, key=lambda x: x[0]) # Bucket by 1st character
>>> sorted(list(s)) # Get the keys
['a', 'b', 'c']
>>> a_iterable = s['a']
>>> next(a_iterable)
'a1'
>>> next(a_iterable)
'a2'
>>> list(s['b'])
['b1', 'b2', 'b3']
The original iterable will be advanced and its items will be cached until
they are used by the child iterables. This may require significant storage.
By default, attempting to select a bucket to which no items belong will
exhaust the iterable and cache all values.
If you specify a *validator* function, selected buckets will instead be
checked against it.
>>> from itertools import count
>>> it = count(1, 2) # Infinite sequence of odd numbers
>>> key = lambda x: x % 10 # Bucket by last digit
>>> validator = lambda x: x in {1, 3, 5, 7, 9} # Odd digits only
>>> s = bucket(it, key=key, validator=validator)
>>> 2 in s
False
>>> list(s[2])
[]
"""
def __init__(self, iterable, key, validator=None):
self._it = iter(iterable)
self._key = key
self._cache = defaultdict(deque)
self._validator = validator or (lambda x: True)
def __contains__(self, value):
if not self._validator(value):
return False
try:
item = next(self[value])
except StopIteration:
return False
else:
self._cache[value].appendleft(item)
return True
def _get_values(self, value):
"""
Helper to yield items from the parent iterator that match *value*.
Items that don't match are stored in the local cache as they
are encountered.
"""
while True:
# If we've cached some items that match the target value, emit
# the first one and evict it from the cache.
if self._cache[value]:
yield self._cache[value].popleft()
# Otherwise we need to advance the parent iterator to search for
# a matching item, caching the rest.
else:
while True:
try:
item = next(self._it)
except StopIteration:
return
item_value = self._key(item)
if item_value == value:
yield item
break
elif self._validator(item_value):
self._cache[item_value].append(item)
def __iter__(self):
for item in self._it:
item_value = self._key(item)
if self._validator(item_value):
self._cache[item_value].append(item)
yield from self._cache.keys()
def __getitem__(self, value):
if not self._validator(value):
return iter(())
return self._get_values(value)
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