Python dict size limit

How to limit the size of a dictionary?

Here’s a simple, no-LRU Python 2.6+ solution (in older Pythons you could do something similar with UserDict.DictMixin , but in 2.6 and better that’s not recommended, and the ABCs from collections are preferable anyway. ):

import collections class MyDict(collections.MutableMapping): def __init__(self, maxlen, *a, **k): self.maxlen = maxlen self.d = dict(*a, **k) while len(self) > maxlen: self.popitem() def __iter__(self): return iter(self.d) def __len__(self): return len(self.d) def __getitem__(self, k): return self.d[k] def __delitem__(self, k): del self.d[k] def __setitem__(self, k, v): if k not in self and len(self) == self.maxlen: self.popitem() self.d[k] = v d = MyDict(5) for i in range(10): d[i] = i print(sorted(d)) 

As other answers mentioned, you probably don’t want to subclass dict — the explicit delegation to self.d is unfortunately boilerplatey but it does guarantee that every other method is properly supplied by collections.MutableMapping .

cachetools will provide you nice implementation of Mapping Hashes that does this (and it works on python 2 and 3).

Excerpt of the documentation:

For the purpose of this module, a cache is a mutable mapping of a fixed maximum size. When the cache is full, i.e. by adding another item the cache would exceed its maximum size, the cache must choose which item(s) to discard based on a suitable cache algorithm.

Python 2.7 and 3.1 have OrderedDict and there are pure-Python implementations for earlier Pythons.

from collections import OrderedDict class LimitedSizeDict(OrderedDict): def __init__(self, *args, **kwds): self.size_limit = kwds.pop("size_limit", None) OrderedDict.__init__(self, *args, **kwds) self._check_size_limit() def __setitem__(self, key, value): OrderedDict.__setitem__(self, key, value) self._check_size_limit() def _check_size_limit(self): if self.size_limit is not None: while len(self) > self.size_limit: self.popitem(last=False) 

You would also have to override other methods that can insert items, such as update . The primary use of OrderedDict is so you can control what gets popped easily, otherwise a normal dict would work.

Here is a simple and efficient LRU cache written with dirt simple Python code that runs on any python version 1.5.2 or later:

class LRU_Cache: def __init__(self, original_function, maxsize=1000): self.original_function = original_function self.maxsize = maxsize self.mapping = <> PREV, NEXT, KEY, VALUE = 0, 1, 2, 3 # link fields self.head = [None, None, None, None] # oldest self.tail = [self.head, None, None, None] # newest self.head[NEXT] = self.tail def __call__(self, *key): PREV, NEXT = 0, 1 mapping, head, tail = self.mapping, self.head, self.tail link = mapping.get(key, head) if link is head: value = self.original_function(*key) if len(mapping) >= self.maxsize: old_prev, old_next, old_key, old_value = head[NEXT] head[NEXT] = old_next old_next[PREV] = head del mapping[old_key] last = tail[PREV] link = [last, tail, key, value] mappingPython dict size limit = last[NEXT] = tail[PREV] = link else: link_prev, link_next, key, value = link link_prev[NEXT] = link_next link_next[PREV] = link_prev last = tail[PREV] last[NEXT] = tail[PREV] = link link[PREV] = last link[NEXT] = tail return value if __name__ == '__main__': p = LRU_Cache(pow, maxsize=3) for i in [1,2,3,4,5,3,1,5,1,1]: print(i, p(i, 2)) 

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Maximum size of a dictionary in python

For example: If you add an element to a deque which has maxlen set, and which is already at maximum size, an element is removed from the other end of the deque: It’s worth noting that Python’s json module doesn’t handle deques, so if you want to dump the deque to json you’ll need to provide a function that converts the deque to a list: To recreate the deque from a json array, just pass the deserialised list to a new deque: Deques are similar to lists, but support efficient appending and popping from both ends, are threadsafe, and can be specified to have a maximum length.

Storage capacity of dictionary and want to store huge data into dictionary in python

The limit of the size of a Python dict depends on the free memory the OS makes available. The problem is that as a dict grows (resizes) it has to copy itself to redistribute the keys so when the dictionary get really huge this process can start to require a lot more memory than is actually available.

Python: Get Size of Dictionary, The len() function is widely used to determine the size of objects in Python. In our case, passing a dictionary object to this function will

How to get the maximum value of a key in dict?

Is it best to split the size by partition, format the number into an int type, and then get the value?

Yes, that’s the way I’d do it:

>>> max(videos.items(), key=lambda i: int.__mul__(*map(int, i[0].split("_")[1:]))) ('size_720_480', 'https://www. ') 

Here’s a slightly more verbose version with a named function:

>>> def get_resolution(key: str) -> int: . """ . Gets the resolution (as pixel area) from 'size_width_height'. . e.g. get_resolution("size_720_480") -> 345600 . """ . _, width, height = key.split("_") . return int(width) * int(height) . >>> max(videos, key=get_resolution) 'size_720_480' 

Given that expression that gives us the largest key, we can easily get the corresponding value:

>>> videos[max(videos, key=get_resolution)] 'https://www. ' 

or we could get the key, value pair by taking the max of items() , here using a much simpler lambda that just translates key, value into get_resolution(key) :

>>> max(videos.items(), key=lambda i: get_resolution(i[0])) ('size_720_480', 'https://www. ') 

Finding all the dicts of max len in a list of dicts, Basically, you add everything in a dictionary to get the maximum dictionary size to be the key, and dictionary list to be the value, and then get that

How to increase Dictionary size in gensim while making Corpus?

Here’s the explaination https://radimrehurek.com/gensim/corpora/dictionary.html. The argument prune_at is setted to 2000000 , depending on the function you are using you can change it to None to avoid the problem of discarding.

EDIT: in gensim/corpora/dictionary.py (line 45 in the current release on the init function) you can set prune_at = None or set your own limit (5000000 for example with prune_at = 5000000 ).

Python — Split Dictionary values on size limit of values, Given a dictionary with string values, the task is to write a python program to split values if the size of string exceeds K.

Python — Ordered List of Dictionaries, With a Size Limit?

One possible solution is to use the double-ended queue implemented in the standard library’s collections package — collections.deque .

Deques are similar to lists, but support efficient appending and popping from both ends, are threadsafe, and can be specified to have a maximum length.

>>> dq = collections.deque(maxlen=5) >>> for i, x in enumerate('abcde'): . dq.append() . >>> dq deque([, , , , ], maxlen=5) 

If you add an element to a deque which has maxlen set, and which is already at maximum size, an element is removed from the other end of the deque:

>>> dq.append() >>> dq deque([, , , , ], maxlen=5) >>> dq.appendleft() >>> dq deque([, , , , ], maxlen=5) 

It’s worth noting that Python’s json module doesn’t handle deques, so if you want to dump the deque to json you’ll need to provide a function that converts the deque to a list:

>>> json.dumps(dq) Traceback (most recent call last): File "", line 1, in . TypeError: Object of type deque is not JSON serializable >>> def jdq(o): . return list(o) . >>> json.dumps(dq, default=jdq) '[, , , , ]' 

To recreate the deque from a json array, just pass the deserialised list to a new deque:

>>> L = json.loads('[, , , , ]') >>> dq = collections.deque(L, maxlen=5) >>> dq deque([, , , , ], maxlen=5) 

Maximum size of a dictionary in Python?, Performance degrades significantly for dictionaries larger than 2^26 = 67,108,864. It takes 30x longer to read from a dictionary of size 2^27 = 134,217,728, and

Источник

Maximum size of a dictionary in python

For example: If you add an element to a deque which has maxlen set, and which is already at maximum size, an element is removed from the other end of the deque: It’s worth noting that Python’s json module doesn’t handle deques, so if you want to dump the deque to json you’ll need to provide a function that converts the deque to a list: To recreate the deque from a json array, just pass the deserialised list to a new deque: Deques are similar to lists, but support efficient appending and popping from both ends, are threadsafe, and can be specified to have a maximum length.

Storage capacity of dictionary and want to store huge data into dictionary in python

The limit of the size of a Python dict depends on the free memory the OS makes available. The problem is that as a dict grows (resizes) it has to copy itself to redistribute the keys so when the dictionary get really huge this process can start to require a lot more memory than is actually available.

Python: Get Size of Dictionary, The len() function is widely used to determine the size of objects in Python. In our case, passing a dictionary object to this function will

How to get the maximum value of a key in dict?

Is it best to split the size by partition, format the number into an int type, and then get the value?

Yes, that’s the way I’d do it:

>>> max(videos.items(), key=lambda i: int.__mul__(*map(int, i[0].split("_")[1:]))) ('size_720_480', 'https://www. ') 

Here’s a slightly more verbose version with a named function:

>>> def get_resolution(key: str) -> int: . """ . Gets the resolution (as pixel area) from 'size_width_height'. . e.g. get_resolution("size_720_480") -> 345600 . """ . _, width, height = key.split("_") . return int(width) * int(height) . >>> max(videos, key=get_resolution) 'size_720_480' 

Given that expression that gives us the largest key, we can easily get the corresponding value:

>>> videos[max(videos, key=get_resolution)] 'https://www. ' 

or we could get the key, value pair by taking the max of items() , here using a much simpler lambda that just translates key, value into get_resolution(key) :

>>> max(videos.items(), key=lambda i: get_resolution(i[0])) ('size_720_480', 'https://www. ') 

Finding all the dicts of max len in a list of dicts, Basically, you add everything in a dictionary to get the maximum dictionary size to be the key, and dictionary list to be the value, and then get that

How to increase Dictionary size in gensim while making Corpus?

Here’s the explaination https://radimrehurek.com/gensim/corpora/dictionary.html. The argument prune_at is setted to 2000000 , depending on the function you are using you can change it to None to avoid the problem of discarding.

EDIT: in gensim/corpora/dictionary.py (line 45 in the current release on the init function) you can set prune_at = None or set your own limit (5000000 for example with prune_at = 5000000 ).

Python — Split Dictionary values on size limit of values, Given a dictionary with string values, the task is to write a python program to split values if the size of string exceeds K.

Python — Ordered List of Dictionaries, With a Size Limit?

One possible solution is to use the double-ended queue implemented in the standard library’s collections package — collections.deque .

Deques are similar to lists, but support efficient appending and popping from both ends, are threadsafe, and can be specified to have a maximum length.

>>> dq = collections.deque(maxlen=5) >>> for i, x in enumerate('abcde'): . dq.append() . >>> dq deque([, , , , ], maxlen=5) 

If you add an element to a deque which has maxlen set, and which is already at maximum size, an element is removed from the other end of the deque:

>>> dq.append() >>> dq deque([, , , , ], maxlen=5) >>> dq.appendleft() >>> dq deque([, , , , ], maxlen=5) 

It’s worth noting that Python’s json module doesn’t handle deques, so if you want to dump the deque to json you’ll need to provide a function that converts the deque to a list:

>>> json.dumps(dq) Traceback (most recent call last): File "", line 1, in . TypeError: Object of type deque is not JSON serializable >>> def jdq(o): . return list(o) . >>> json.dumps(dq, default=jdq) '[, , , , ]' 

To recreate the deque from a json array, just pass the deserialised list to a new deque:

>>> L = json.loads('[, , , , ]') >>> dq = collections.deque(L, maxlen=5) >>> dq deque([, , , , ], maxlen=5) 

Maximum size of a dictionary in Python?, Performance degrades significantly for dictionaries larger than 2^26 = 67,108,864. It takes 30x longer to read from a dictionary of size 2^27 = 134,217,728, and

Источник