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...dict" test as well as the new "for key in dict:" to iterate efficiently (without making a copy of the list of keys) over all keys in a dictionary. It doesn't require the other argument to be a defaultdict or even a dictionary: any mapping object that supports "for key in other" and other[key] will do. Here's the new type at work: >>> print defaultdict # show our type <class '__main__.defaultdict'> >>> print type(defaultdict) # its metatype ...
...dict" test as well as the new "for key in dict:" to iterate efficiently (without making a copy of the list of keys) over all keys in a dictionary. It doesn't require the other argument to be a defaultdict or even a dictionary: any mapping object that supports "for key in other" and other[key] will do. Here's the new type at work: >>> print defaultdict # show our type <class '__main__.defaultdict'> >>> print type(defaultdict) # its metatype <type 'type'...
...dict. Why "frozenmap" and not "frozendict" "Dict" has a very specific meaning in Python: a dict is a concrete implementation of abc.MutableMapping with O(1) get and set operations (frozenmap has O(log N) complexity); Python dicts preserve insertion order. The proposed frozenmap does not have these mentioned properties. Instead, frozenmap has an O(log N) cost of set/get operations, and it only implements the abc.Mapping protocol. Implementation The full implementation of t...
...dict. Why "frozenmap" and not "frozendict" "Dict" has a very specific meaning in Python: a dict is a concrete implementation of abc.MutableMapping with O(1) get and set operations (frozenmap has O(log N) complexity); Python dicts preserve insertion order. The proposed frozenmap does not have these mentioned properties. Instead, frozenmap has an O(log N) cost of set/get operations, and it only implements the abc.Mapping protocol. Implementation The full implementation of the proposed froze...
...dictionary does not change the keys table, it simply removes the value from the values array. Combined-Table dictionaries Explicit dictionaries (dict() or {}), module dictionaries and most other dictionaries are created as combined-table dictionaries. A combined-table dictionary never becomes a split-table dictionary. Combined tables are laid out in much the same way as the tables in the old dictionary, resulting in very similar performance. Implementation The new dictionary implementation...
...Dict. This would then be used as the mapping proxied as __dict__. Doing so would mostly provide the same semantics. However, using OrderedDict for __dict__ would obscure the relationship with the definition namespace, making it less useful. Additionally, (in the case of OrderedDict specifically) doing this would require significant changes to the semantics of the concrete dict C-API. There has been some discussion about moving to a compact dict implementation which would (mostly) preserve inse...
...dict, to distinguish it from the type dict. In the more complicated case, there's a conflict between names stored in the instance dict and names stored in the type dict. If both dicts have an entry with the same key, which one should we return? Looking at classic Python for guidance, I find conflicting rules: for class instances, the instance dict overrides the class dict, except for the special attributes (like __dict__ and __class__), which have priority over the instance dict. I resolved t...
...Dict): x: int class Y(TypedDict): y: str class XYZ(X, Y): z: bool The TypedDict XYZ has three items: x (type int), y (type str), and z (type bool). A TypedDict cannot inherit from both a TypedDict type and a non-TypedDict base class. Additional notes on TypedDict class inheritance: Changing a field type of a parent TypedDict class in a subclass is not allowed. Example: class X(TypedDict): x: str class Y(X): x: int # Type check error: cannot overwrite TypedDict field "x" ...
...dict(), whose mapping/iterator parameter is optional and semantically must be positional-only. Any externally visible name for this parameter would occlude that name going into the **kwarg keyword variadic parameter dict! [1] Obviously one can simulate any of these in pure Python code by accepting (*args, **kwargs) and parsing the arguments by hand. But this results in a disconnect between the Python function's signature and what it actually accepts, not to mention the work of implementing sa...
...dict() - two new features for dict construction: keyword arguments to the dict() constructor are now a shorthand for creating a dictionary from the key/value pairs, and dict.fromkeys(iterable) returns a dict whose keys are taken from the given iterable (the values default to None). Also a new dict method was added, pop(key), which removes and returns the value corresponding to the given key. filter() - now returns Unicode when the input is Unicode. Various bugs with subclasses of built-in types...
...dict comprehensions and generator expressions. Rationale and Goals Python has extensive support for synchronous comprehensions, allowing to produce lists, dicts, and sets with a simple and concise syntax. We propose implementing similar syntactic constructions for the asynchronous code. To illustrate the readability improvement, consider the following example: result = [] async for i in aiter(): if i % 2: result.append(i) With the proposed asynchronous comprehensions syntax, the...
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Released: Aug. 30, 2021
This is the seventh maintenance release of Python 3.9 Note: The release you're looking at is Python 3.9.7, a bugfix release for the legacy 3.9 series. Python 3.11 is now the latest feature release series of Python 3. Get the latest release of 3.11.x here. There's been 187 commits …
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Released: March 23, 2022
This is the twelfth maintenance release of Python 3.9 Note: The release you're looking at is Python 3.9.12, a bugfix release for the legacy 3.9 series. Python 3.11 is now the latest feature release series of Python 3. Get the latest release of 3.11.x here. This is a special …
...dict # typing.Dict set # typing.Set frozenset # typing.FrozenSet type # typing.Type collections.deque collections.defaultdict collections.OrderedDict collections.Counter collections.ChainMap collections.abc.Awaitable collections.abc.Coroutine collections.abc.AsyncIterable collections.abc.AsyncIterator collections.abc.AsyncGenerator collections.abc.Iterable collections.abc.Iterator collections.abc.Generator collections.abc.Reversible collections.abc.Container collections.abc.Collection collec...
Released: April 28, 2020
This is an early developer preview of Python 3.9 Python 3.9 is still in development. This release, 3.9.0a6 is the last out of six planned alpha releases. Alpha releases are intended to make it easier to test the current state of new features and bug fixes and to test the …
...dict for backing storage. (The real implementation uses a HAMT, which is semantically equivalent to a dict but with different performance trade-offs.): class Context(collections.abc.Mapping): def __init__(self): self._data = {} self._in_use = False def __getitem__(self, key): return self._data[key] def __iter__(self): return iter(self._data) def __len__(self): return len(self._data) At any given moment, the threadstate holds a current ...
Released: May 3, 2021
This is the fifth maintenance release of Python 3.9 Note: The release you're looking at is Python 3.9.5, a bugfix release for the legacy 3.9 series. Python 3.11 is now the latest feature release series of Python 3. Get the latest release of 3.11.x here. There's been 111 commits …
Released: Jan. 14, 2022
This is the ninth maintenance release of Python 3.9 Note: The release you're looking at is Python 3.9.10, a bugfix release for the legacy 3.9 series. Python 3.11 is now the latest feature release series of Python 3. Get the latest release of 3.11.x here. Major new features of …
...dict, d[1] has a positional index of 1 and also a final index of 1 (because it's the element that is then added to the dictionary) and d[1, 2] has positional index of (1, 2) and final index also of (1, 2) (because yet again it's the element that is added to the dictionary). However, the positional index d[1,2:3] is not accepted by the dictionary, because there's no way to transform the positional index into a final index, as the slice object is unhashable. The positional index is what is current...
Released: July 3, 2020
This is a beta preview of Python 3.9 Python 3.9 is still in development. This release, 3.9.0b4, is the fourth of five planned beta release previews. Beta release previews are intended to give the wider community the opportunity to test new features and bug fixes and to prepare their projects …