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persistent.py
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1362 lines (1021 loc) · 34.9 KB
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"""Persistent Data Types
"""
import operator as op
import sys
from collections import OrderedDict
from itertools import islice
from shutil import rmtree
from tempfile import mkdtemp
from .core import BytesType, Cache, ENOVAL, TextType, Timeout
############################################################################
# BEGIN Python 2/3 Shims
############################################################################
try:
from collections.abc import MutableMapping, Sequence
from collections.abc import KeysView, ValuesView, ItemsView
except ImportError:
from collections import MutableMapping, Sequence
from collections import KeysView, ValuesView, ItemsView
if sys.hexversion < 0x03000000:
from itertools import izip as zip # pylint: disable=redefined-builtin,no-name-in-module,ungrouped-imports
range = xrange # pylint: disable=redefined-builtin,invalid-name,undefined-variable
############################################################################
# END Python 2/3 Shims
############################################################################
def _make_compare(seq_op, doc):
"Make compare method with Sequence semantics."
def compare(self, that):
"Compare method for deque and sequence."
if not isinstance(that, Sequence):
return NotImplemented
len_self = len(self)
len_that = len(that)
if len_self != len_that:
if seq_op is op.eq:
return False
if seq_op is op.ne:
return True
for alpha, beta in zip(self, that):
if alpha != beta:
return seq_op(alpha, beta)
return seq_op(len_self, len_that)
compare.__name__ = '__{0}__'.format(seq_op.__name__)
doc_str = 'Return True if and only if deque is {0} `that`.'
compare.__doc__ = doc_str.format(doc)
return compare
class Deque(Sequence):
"""Persistent sequence with double-ended queue semantics.
Double-ended queue is an ordered collection with optimized access at its
endpoints.
Items are serialized to disk. Deque may be initialized from directory path
where items are stored.
>>> deque = Deque(directory='/tmp/diskcache/deque')
>>> deque
Deque(directory='/tmp/diskcache/deque')
>>> deque.clear()
>>> deque += range(5)
>>> list(deque)
[0, 1, 2, 3, 4]
>>> for value in range(5):
... deque.appendleft(-value)
>>> len(deque)
10
>>> list(deque)
[-4, -3, -2, -1, 0, 0, 1, 2, 3, 4]
>>> deque.pop()
4
>>> deque.popleft()
-4
>>> deque.reverse()
>>> list(deque)
[3, 2, 1, 0, 0, -1, -2, -3]
"""
def __init__(self, iterable=(), directory=None):
"""Initialize deque instance.
If directory is None then temporary directory created. The directory
will *not* be automatically removed.
:param iterable: iterable of items to append to deque
:param directory: deque directory (default None)
"""
if directory is None:
directory = mkdtemp()
self._cache = Cache(directory, eviction_policy='none')
self.extend(iterable)
@classmethod
def fromcache(cls, cache, iterable=()):
"""Initialize deque using `cache`.
>>> cache = Cache('/tmp/diskcache/index')
>>> _ = cache.clear()
>>> deque = Deque.fromcache(cache, [5, 6, 7, 8])
>>> len(deque)
4
>>> 7 in deque
True
>>> deque.popleft()
5
:param Cache cache: cache to use
:param iterable: iterable of items
:return: initialized Deque
"""
# pylint: disable=no-member,protected-access
self = cls.__new__(cls)
self._cache = cache
self.extend(iterable)
return self
@property
def directory(self):
"Directory path where deque is stored."
return self._cache.directory
def _key(self, index):
len_self = len(self)
if index < 0:
index += len_self
if index < 0:
raise IndexError('deque index out of range')
elif index >= len_self:
raise IndexError('deque index out of range')
diff = len_self - index - 1
_cache_iterkeys = self._cache.iterkeys
try:
if index <= diff:
iter_keys = _cache_iterkeys()
key = next(islice(iter_keys, index, index + 1))
else:
iter_keys = _cache_iterkeys(reverse=True)
key = next(islice(iter_keys, diff, diff + 1))
except StopIteration:
raise IndexError('deque index out of range')
return key
def __getitem__(self, index):
"""deque.__getitem__(index) <==> deque[index]
Return corresponding item for `index` in deque.
>>> deque = Deque(directory='/tmp/diskcache/deque')
>>> deque.clear()
>>> deque.extend('abcde')
>>> deque[0]
'a'
>>> deque[-1]
'e'
>>> deque[2]
'c'
:param int index: index of item
:return: corresponding item
:raises IndexError: if index out of range
"""
_key = self._key
_cache = self._cache
while True:
try:
key = _key(index)
return _cache[key]
except (KeyError, Timeout):
continue
def __setitem__(self, index, value):
"""deque.__setitem__(index, value) <==> deque[index] = value
Store `value` in deque at `index`.
>>> deque = Deque(directory='/tmp/diskcache/deque')
>>> deque.clear()
>>> deque.extend([None] * 3)
>>> deque[0] = 'a'
>>> deque[1] = 'b'
>>> deque[-1] = 'c'
>>> ''.join(deque)
'abc'
:param int index: index of value
:param value: value to store
:raises IndexError: if index out of range
"""
_key = self._key
_cache = self._cache
while True:
try:
key = _key(index)
_cache[key] = value
return
except Timeout:
continue
def __delitem__(self, index):
"""deque.__delitem__(index) <==> del deque[index]
Delete item in deque at `index`.
>>> deque = Deque(directory='/tmp/diskcache/deque')
>>> deque.clear()
>>> deque.extend([None] * 3)
>>> del deque[0]
>>> del deque[1]
>>> del deque[-1]
>>> len(deque)
0
:param int index: index of item
:raises IndexError: if index out of range
"""
_key = self._key
_cache = self._cache
while True:
try:
key = _key(index)
del _cache[key]
return
except (KeyError, Timeout):
continue
def __repr__(self):
"""deque.__repr__() <==> repr(deque)
Return string with printable representation of deque.
"""
name = type(self).__name__
return '{0}(directory={1!r})'.format(name, self.directory)
__eq__ = _make_compare(op.eq, 'equal to')
__ne__ = _make_compare(op.ne, 'not equal to')
__lt__ = _make_compare(op.lt, 'less than')
__gt__ = _make_compare(op.gt, 'greater than')
__le__ = _make_compare(op.le, 'less than or equal to')
__ge__ = _make_compare(op.ge, 'greater than or equal to')
def __iadd__(self, iterable):
"""deque.__iadd__(iterable) <==> deque += iterable
Extend back side of deque with items from iterable.
"""
self.extend(iterable)
return self
def __iter__(self):
"""deque.__iter__() <==> iter(deque)
Return iterator of deque from front to back.
"""
_cache = self._cache
for key in _cache.iterkeys():
try:
yield _cache[key]
except (KeyError, Timeout):
pass
def __len__(self):
"""deque.__len__() <==> len(deque)
Return length of deque.
"""
return len(self._cache)
def __reversed__(self):
"""deque.__reversed__() <==> reversed(deque)
Return iterator of deque from back to front.
>>> deque = Deque(directory='/tmp/diskcache/deque')
>>> deque.clear()
>>> deque.extend('abcd')
>>> iterator = reversed(deque)
>>> next(iterator)
'd'
>>> list(iterator)
['c', 'b', 'a']
"""
_cache = self._cache
for key in _cache.iterkeys(reverse=True):
try:
yield _cache[key]
except (KeyError, Timeout):
pass
def __getstate__(self):
return self.directory
def __setstate__(self, state):
self.__init__(directory=state)
def append(self, value):
"""Add `value` to back of deque.
>>> deque = Deque(directory='/tmp/diskcache/deque')
>>> deque.clear()
>>> deque.append('a')
>>> deque.append('b')
>>> deque.append('c')
>>> list(deque)
['a', 'b', 'c']
:param value: value to add to back of deque
"""
_cache_push = self._cache.push
while True:
try:
_cache_push(value)
return
except Timeout:
continue
def appendleft(self, value):
"""Add `value` to front of deque.
>>> deque = Deque(directory='/tmp/diskcache/deque')
>>> deque.clear()
>>> deque.appendleft('a')
>>> deque.appendleft('b')
>>> deque.appendleft('c')
>>> list(deque)
['c', 'b', 'a']
:param value: value to add to front of deque
"""
_cache_push = self._cache.push
while True:
try:
_cache_push(value, side='front')
return
except Timeout:
continue
def clear(self):
"""Remove all elements from deque.
"""
_cache_clear = self._cache.clear
while True:
try:
_cache_clear()
return
except Timeout:
continue
def count(self, value):
"""Return number of occurrences of `value` in deque.
>>> deque = Deque(directory='/tmp/diskcache/deque')
>>> deque.clear()
>>> deque += [num for num in range(1, 5) for _ in range(num)]
>>> deque.count(0)
0
>>> deque.count(1)
1
>>> deque.count(4)
4
:param value: value to count in deque
"""
return sum(1 for item in self if item == value)
def extend(self, iterable):
"""Extend back side of deque with values from `iterable`.
:param iterable: iterable of values
"""
for value in iterable:
self.append(value)
def extendleft(self, iterable):
"""Extend front side of deque with value from `iterable`.
>>> deque = Deque(directory='/tmp/diskcache/deque')
>>> deque.clear()
>>> deque.extendleft('abc')
>>> list(deque)
['c', 'b', 'a']
:param iterable: iterable of values
"""
for value in iterable:
self.appendleft(value)
def pop(self):
"""Remove and return value at back of deque.
If deque is empty then raise IndexError.
>>> deque = Deque(directory='/tmp/diskcache/deque')
>>> deque.clear()
>>> deque += 'ab'
>>> deque.pop()
'b'
>>> deque.pop()
'a'
>>> deque.pop()
Traceback (most recent call last):
...
IndexError: pop from an empty deque
:raises IndexError: if deque is empty
"""
_cache_pull = self._cache.pull
while True:
try:
default = None, ENOVAL
_, value = _cache_pull(default=default, side='back')
except Timeout:
continue
else:
if value is ENOVAL:
raise IndexError('pop from an empty deque')
return value
def popleft(self):
"""Remove and return value at front of deque.
>>> deque = Deque(directory='/tmp/diskcache/deque')
>>> deque.clear()
>>> deque += 'ab'
>>> deque.popleft()
'a'
>>> deque.popleft()
'b'
>>> deque.popleft()
Traceback (most recent call last):
...
IndexError: pop from an empty deque
"""
_cache_pull = self._cache.pull
while True:
try:
default = None, ENOVAL
_, value = _cache_pull(default=default)
except Timeout:
continue
else:
if value is ENOVAL:
raise IndexError('pop from an empty deque')
return value
def remove(self, value):
"""Remove first occurrence of `value` in deque.
>>> deque = Deque(directory='/tmp/diskcache/deque')
>>> deque.clear()
>>> deque += 'aab'
>>> deque.remove('a')
>>> list(deque)
['a', 'b']
>>> deque.remove('b')
>>> list(deque)
['a']
>>> deque.remove('c')
Traceback (most recent call last):
...
ValueError: deque.remove(value): value not in deque
:param value: value to remove
:raises ValueError: if value not in deque
"""
_cache = self._cache
for key in _cache.iterkeys():
try:
while True:
try:
item = _cache[key]
except Timeout:
continue
else:
break
except KeyError:
continue
else:
if value == item:
try:
while True:
try:
del _cache[key]
except Timeout:
continue
else:
return
except KeyError:
continue
raise ValueError('deque.remove(value): value not in deque')
def reverse(self):
"""Reverse deque in place.
"""
# pylint: disable=protected-access
directory = mkdtemp()
temp = None
try:
temp = Deque(iterable=reversed(self), directory=directory)
self.clear()
self.extend(temp)
finally:
if temp is not None:
temp._cache.close()
del temp
rmtree(directory)
def rotate(self, steps=1):
"""Rotate deque right by `steps`.
If steps is negative then rotate left.
>>> deque = Deque(directory='/tmp/diskcache/deque')
>>> deque.clear()
>>> deque += range(5)
>>> deque.rotate(2)
>>> list(deque)
[3, 4, 0, 1, 2]
>>> deque.rotate(-1)
>>> list(deque)
[4, 0, 1, 2, 3]
:param int steps: number of steps to rotate (default 1)
"""
if not isinstance(steps, int):
type_name = type(steps).__name__
raise TypeError('integer argument expected, got %s' % type_name)
len_self = len(self)
if not len_self:
return
if steps >= 0:
steps %= len_self
for _ in range(steps):
try:
value = self.pop()
except IndexError:
return
else:
self.appendleft(value)
else:
steps *= -1
steps %= len_self
for _ in range(steps):
try:
value = self.popleft()
except IndexError:
return
else:
self.append(value)
def __del__(self):
self._cache.close()
__hash__ = None
class Index(MutableMapping):
"""Persistent mutable mapping with insertion order iteration.
Items are serialized to disk. Index may be initialized from directory path
where items are stored.
Hashing protocol is not used. Keys are looked up by their serialized
format. See ``diskcache.Disk`` for details.
>>> index = Index('/tmp/diskcache/index')
>>> index
Index('/tmp/diskcache/index')
>>> index.clear()
>>> index.update([('a', 1), ('b', 2), ('c', 3)])
>>> index['a']
1
>>> list(index)
['a', 'b', 'c']
>>> len(index)
3
>>> del index['b']
>>> index.popitem()
('c', 3)
"""
def __init__(self, *args, **kwargs):
"""Initialize index in directory and update items.
Optional first argument may be string specifying directory where items
are stored. When None or not given, temporary directory is created.
>>> index = Index({'a': 1, 'b': 2, 'c': 3})
>>> len(index)
3
>>> directory = index.directory
>>> inventory = Index(directory, d=4)
>>> inventory['b']
2
>>> len(inventory)
4
"""
if args and isinstance(args[0], (BytesType, TextType)):
directory = args[0]
args = args[1:]
else:
if args and args[0] is None:
args = args[1:]
directory = mkdtemp(prefix='diskcache-')
self._cache = Cache(directory, eviction_policy='none')
self.update(*args, **kwargs)
@classmethod
def fromcache(cls, cache, *args, **kwargs):
"""Initialize index using `cache` and update items.
>>> cache = Cache('/tmp/diskcache/index')
>>> _ = cache.clear()
>>> index = Index.fromcache(cache, {'a': 1, 'b': 2, 'c': 3})
>>> len(index)
3
>>> 'b' in index
True
>>> index['c']
3
:param Cache cache: cache to use
:param args: mapping or sequence of items
:param kwargs: mapping of items
:return: initialized Index
"""
# pylint: disable=no-member,protected-access
self = cls.__new__(cls)
self._cache = cache
self.update(*args, **kwargs)
return self
@property
def directory(self):
"Directory path where items are stored."
return self._cache.directory
def __getitem__(self, key):
"""index.__getitem__(key) <==> index[key]
Return corresponding value for `key` in index.
>>> index = Index('/tmp/diskcache/index')
>>> index.clear()
>>> index.update({'a': 1, 'b': 2})
>>> index['a']
1
>>> index['b']
2
>>> index['c']
Traceback (most recent call last):
...
KeyError: 'c'
:param key: key for item
:return: value for item in index with given key
:raises KeyError: if key is not found
"""
_cache = self._cache
while True:
try:
return _cache[key]
except Timeout:
continue
def __setitem__(self, key, value):
"""index.__setitem__(key, value) <==> index[key] = value
Set `key` and `value` item in index.
>>> index = Index('/tmp/diskcache/index')
>>> index.clear()
>>> index['a'] = 1
>>> index[0] = None
>>> len(index)
2
:param key: key for item
:param value: value for item
"""
_cache = self._cache
while True:
try:
_cache[key] = value
except Timeout:
continue
else:
return
def __delitem__(self, key):
"""index.__delitem__(key) <==> del index[key]
Delete corresponding item for `key` from index.
>>> index = Index('/tmp/diskcache/index')
>>> index.clear()
>>> index.update({'a': 1, 'b': 2})
>>> del index['a']
>>> del index['b']
>>> len(index)
0
>>> del index['c']
Traceback (most recent call last):
...
KeyError: 'c'
:param key: key for item
:raises KeyError: if key is not found
"""
_cache = self._cache
while True:
try:
del _cache[key]
except Timeout:
continue
else:
return
def setdefault(self, key, default=None):
"""Set and get value for `key` in index using `default`.
If `key` is not in index then set corresponding value to `default`. If
`key` is in index then ignore `default` and return existing value.
>>> index = Index('/tmp/diskcache/index')
>>> index.clear()
>>> index.setdefault('a', 0)
0
>>> index.setdefault('a', 1)
0
:param key: key for item
:param default: value if key is missing (default None)
:return: value for item in index with given key
"""
_cache = self._cache
while True:
try:
return self[key]
except KeyError:
while True:
try:
_cache.add(key, default)
except Timeout:
continue
else:
break
def pop(self, key, default=ENOVAL):
"""Remove corresponding item for `key` from index and return value.
If `key` is missing then return `default`. If `default` is `ENOVAL`
then raise KeyError.
>>> index = Index('/tmp/diskcache/index', {'a': 1, 'b': 2})
>>> index.pop('a')
1
>>> index.pop('b')
2
>>> index.pop('c', default=3)
3
>>> index.pop('d')
Traceback (most recent call last):
...
KeyError: 'd'
:param key: key for item
:param default: return value if key is missing (default ENOVAL)
:return: value for item if key is found else default
:raises KeyError: if key is not found and default is ENOVAL
"""
_cache = self._cache
while True:
try:
value = _cache.pop(key, default=default)
except Timeout:
continue
else:
if value is ENOVAL:
raise KeyError(key)
return value
def popitem(self, last=True):
"""Remove and return item pair.
Item pairs are returned in last-in-first-out (LIFO) order if last is
True else first-in-first-out (FIFO) order. LIFO order imitates a stack
and FIFO order imitates a queue.
>>> index = Index('/tmp/diskcache/index')
>>> index.clear()
>>> index.update([('a', 1), ('b', 2), ('c', 3)])
>>> index.popitem()
('c', 3)
>>> index.popitem(last=False)
('a', 1)
>>> index.popitem()
('b', 2)
>>> index.popitem()
Traceback (most recent call last):
...
KeyError
:param bool last: pop last item pair (default True)
:return: key and value item pair
:raises KeyError: if index is empty
"""
# pylint: disable=arguments-differ
_cache = self._cache
while True:
try:
if last:
key = next(reversed(_cache))
else:
key = next(iter(_cache))
except StopIteration:
raise KeyError
try:
value = _cache.pop(key)
except (KeyError, Timeout):
continue
else:
return key, value
def push(self, value, prefix=None, side='back'):
"""Push `value` onto `side` of queue in index identified by `prefix`.
When prefix is None, integer keys are used. Otherwise, string keys are
used in the format "prefix-integer". Integer starts at 500 trillion.
Defaults to pushing value on back of queue. Set side to 'front' to push
value on front of queue. Side must be one of 'back' or 'front'.
See also `Index.pull`.
>>> index = Index('/tmp/diskcache/index')
>>> index.clear()
>>> print(index.push('apples'))
500000000000000
>>> print(index.push('beans'))
500000000000001
>>> print(index.push('cherries', side='front'))
499999999999999
>>> index[500000000000001]
'beans'
>>> index.push('dates', prefix='fruit')
'fruit-500000000000000'
:param value: value for item
:param str prefix: key prefix (default None, key is integer)
:param str side: either 'back' or 'front' (default 'back')
:return: key for item in cache
"""
_cache_push = self._cache.push
while True:
try:
return _cache_push(value, prefix, side)
except Timeout:
continue
def pull(self, prefix=None, default=(None, None), side='front'):
"""Pull key and value item pair from `side` of queue in index.
When prefix is None, integer keys are used. Otherwise, string keys are
used in the format "prefix-integer". Integer starts at 500 trillion.
If queue is empty, return default.
Defaults to pulling key and value item pairs from front of queue. Set
side to 'back' to pull from back of queue. Side must be one of 'front'
or 'back'.
See also `Index.push`.
>>> index = Index('/tmp/diskcache/index')
>>> index.clear()
>>> for letter in 'abc':
... print(index.push(letter))
500000000000000
500000000000001
500000000000002
>>> key, value = index.pull()
>>> print(key)
500000000000000
>>> value
'a'
>>> _, value = index.pull(side='back')