You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
772 lines
26 KiB
772 lines
26 KiB
2 years ago
|
Metadata-Version: 2.1
|
||
|
Name: pyrsistent
|
||
|
Version: 0.18.1
|
||
|
Summary: Persistent/Functional/Immutable data structures
|
||
|
Home-page: http://github.com/tobgu/pyrsistent/
|
||
|
Author: Tobias Gustafsson
|
||
|
Author-email: tobias.l.gustafsson@gmail.com
|
||
|
License: MIT
|
||
|
Platform: UNKNOWN
|
||
|
Classifier: Intended Audience :: Developers
|
||
|
Classifier: License :: OSI Approved :: MIT License
|
||
|
Classifier: Operating System :: OS Independent
|
||
|
Classifier: Programming Language :: Python :: 3.7
|
||
|
Classifier: Programming Language :: Python :: 3.8
|
||
|
Classifier: Programming Language :: Python :: 3.9
|
||
|
Classifier: Programming Language :: Python :: 3.10
|
||
|
Classifier: Programming Language :: Python :: Implementation :: PyPy
|
||
|
Requires-Python: >=3.7
|
||
|
Description-Content-Type: text/x-rst
|
||
|
License-File: LICENSE.mit
|
||
|
|
||
|
Pyrsistent
|
||
|
==========
|
||
|
.. image:: https://github.com/tobgu/pyrsistent/actions/workflows/tests.yaml/badge.svg
|
||
|
:target: https://github.com/tobgu/pyrsistent/actions/workflows/tests.yaml
|
||
|
|
||
|
|
||
|
.. _Pyrthon: https://www.github.com/tobgu/pyrthon/
|
||
|
|
||
|
Pyrsistent is a number of persistent collections (by some referred to as functional data structures). Persistent in
|
||
|
the sense that they are immutable.
|
||
|
|
||
|
All methods on a data structure that would normally mutate it instead return a new copy of the structure containing the
|
||
|
requested updates. The original structure is left untouched.
|
||
|
|
||
|
This will simplify the reasoning about what a program does since no hidden side effects ever can take place to these
|
||
|
data structures. You can rest assured that the object you hold a reference to will remain the same throughout its
|
||
|
lifetime and need not worry that somewhere five stack levels below you in the darkest corner of your application
|
||
|
someone has decided to remove that element that you expected to be there.
|
||
|
|
||
|
Pyrsistent is influenced by persistent data structures such as those found in the standard library of Clojure. The
|
||
|
data structures are designed to share common elements through path copying.
|
||
|
It aims at taking these concepts and make them as pythonic as possible so that they can be easily integrated into any python
|
||
|
program without hassle.
|
||
|
|
||
|
If you want to go all in on persistent data structures and use literal syntax to define them in your code rather
|
||
|
than function calls check out Pyrthon_.
|
||
|
|
||
|
Examples
|
||
|
--------
|
||
|
.. _Sequence: collections_
|
||
|
.. _Hashable: collections_
|
||
|
.. _Mapping: collections_
|
||
|
.. _Mappings: collections_
|
||
|
.. _Set: collections_
|
||
|
.. _collections: https://docs.python.org/3/library/collections.abc.html
|
||
|
.. _documentation: http://pyrsistent.readthedocs.org/
|
||
|
|
||
|
The collection types and key features currently implemented are:
|
||
|
|
||
|
* PVector_, similar to a python list
|
||
|
* PMap_, similar to dict
|
||
|
* PSet_, similar to set
|
||
|
* PRecord_, a PMap on steroids with fixed fields, optional type and invariant checking and much more
|
||
|
* PClass_, a Python class fixed fields, optional type and invariant checking and much more
|
||
|
* `Checked collections`_, PVector, PMap and PSet with optional type and invariance checks and more
|
||
|
* PBag, similar to collections.Counter
|
||
|
* PList, a classic singly linked list
|
||
|
* PDeque, similar to collections.deque
|
||
|
* Immutable object type (immutable) built on the named tuple
|
||
|
* freeze_ and thaw_ functions to convert between pythons standard collections and pyrsistent collections.
|
||
|
* Flexible transformations_ of arbitrarily complex structures built from PMaps and PVectors.
|
||
|
|
||
|
Below are examples of common usage patterns for some of the structures and features. More information and
|
||
|
full documentation for all data structures is available in the documentation_.
|
||
|
|
||
|
.. _PVector:
|
||
|
|
||
|
PVector
|
||
|
~~~~~~~
|
||
|
With full support for the Sequence_ protocol PVector is meant as a drop in replacement to the built in list from a readers
|
||
|
point of view. Write operations of course differ since no in place mutation is done but naming should be in line
|
||
|
with corresponding operations on the built in list.
|
||
|
|
||
|
Support for the Hashable_ protocol also means that it can be used as key in Mappings_.
|
||
|
|
||
|
Appends are amortized O(1). Random access and insert is log32(n) where n is the size of the vector.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> from pyrsistent import v, pvector
|
||
|
|
||
|
# No mutation of vectors once created, instead they
|
||
|
# are "evolved" leaving the original untouched
|
||
|
>>> v1 = v(1, 2, 3)
|
||
|
>>> v2 = v1.append(4)
|
||
|
>>> v3 = v2.set(1, 5)
|
||
|
>>> v1
|
||
|
pvector([1, 2, 3])
|
||
|
>>> v2
|
||
|
pvector([1, 2, 3, 4])
|
||
|
>>> v3
|
||
|
pvector([1, 5, 3, 4])
|
||
|
|
||
|
# Random access and slicing
|
||
|
>>> v3[1]
|
||
|
5
|
||
|
>>> v3[1:3]
|
||
|
pvector([5, 3])
|
||
|
|
||
|
# Iteration
|
||
|
>>> list(x + 1 for x in v3)
|
||
|
[2, 6, 4, 5]
|
||
|
>>> pvector(2 * x for x in range(3))
|
||
|
pvector([0, 2, 4])
|
||
|
|
||
|
.. _PMap:
|
||
|
|
||
|
PMap
|
||
|
~~~~
|
||
|
With full support for the Mapping_ protocol PMap is meant as a drop in replacement to the built in dict from a readers point
|
||
|
of view. Support for the Hashable_ protocol also means that it can be used as key in other Mappings_.
|
||
|
|
||
|
Random access and insert is log32(n) where n is the size of the map.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> from pyrsistent import m, pmap, v
|
||
|
|
||
|
# No mutation of maps once created, instead they are
|
||
|
# "evolved" leaving the original untouched
|
||
|
>>> m1 = m(a=1, b=2)
|
||
|
>>> m2 = m1.set('c', 3)
|
||
|
>>> m3 = m2.set('a', 5)
|
||
|
>>> m1
|
||
|
pmap({'a': 1, 'b': 2})
|
||
|
>>> m2
|
||
|
pmap({'a': 1, 'c': 3, 'b': 2})
|
||
|
>>> m3
|
||
|
pmap({'a': 5, 'c': 3, 'b': 2})
|
||
|
>>> m3['a']
|
||
|
5
|
||
|
|
||
|
# Evolution of nested persistent structures
|
||
|
>>> m4 = m(a=5, b=6, c=v(1, 2))
|
||
|
>>> m4.transform(('c', 1), 17)
|
||
|
pmap({'a': 5, 'c': pvector([1, 17]), 'b': 6})
|
||
|
>>> m5 = m(a=1, b=2)
|
||
|
|
||
|
# Evolve by merging with other mappings
|
||
|
>>> m5.update(m(a=2, c=3), {'a': 17, 'd': 35})
|
||
|
pmap({'a': 17, 'c': 3, 'b': 2, 'd': 35})
|
||
|
>>> pmap({'x': 1, 'y': 2}) + pmap({'y': 3, 'z': 4})
|
||
|
pmap({'y': 3, 'x': 1, 'z': 4})
|
||
|
|
||
|
# Dict-like methods to convert to list and iterate
|
||
|
>>> m3.items()
|
||
|
pvector([('a', 5), ('c', 3), ('b', 2)])
|
||
|
>>> list(m3)
|
||
|
['a', 'c', 'b']
|
||
|
|
||
|
.. _PSet:
|
||
|
|
||
|
PSet
|
||
|
~~~~
|
||
|
With full support for the Set_ protocol PSet is meant as a drop in replacement to the built in set from a readers point
|
||
|
of view. Support for the Hashable_ protocol also means that it can be used as key in Mappings_.
|
||
|
|
||
|
Random access and insert is log32(n) where n is the size of the set.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> from pyrsistent import s
|
||
|
|
||
|
# No mutation of sets once created, you know the story...
|
||
|
>>> s1 = s(1, 2, 3, 2)
|
||
|
>>> s2 = s1.add(4)
|
||
|
>>> s3 = s1.remove(1)
|
||
|
>>> s1
|
||
|
pset([1, 2, 3])
|
||
|
>>> s2
|
||
|
pset([1, 2, 3, 4])
|
||
|
>>> s3
|
||
|
pset([2, 3])
|
||
|
|
||
|
# Full support for set operations
|
||
|
>>> s1 | s(3, 4, 5)
|
||
|
pset([1, 2, 3, 4, 5])
|
||
|
>>> s1 & s(3, 4, 5)
|
||
|
pset([3])
|
||
|
>>> s1 < s2
|
||
|
True
|
||
|
>>> s1 < s(3, 4, 5)
|
||
|
False
|
||
|
|
||
|
.. _PRecord:
|
||
|
|
||
|
PRecord
|
||
|
~~~~~~~
|
||
|
A PRecord is a PMap with a fixed set of specified fields. Records are declared as python classes inheriting
|
||
|
from PRecord. Because it is a PMap it has full support for all Mapping methods such as iteration and element
|
||
|
access using subscript notation.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> from pyrsistent import PRecord, field
|
||
|
>>> class ARecord(PRecord):
|
||
|
... x = field()
|
||
|
...
|
||
|
>>> r = ARecord(x=3)
|
||
|
>>> r
|
||
|
ARecord(x=3)
|
||
|
>>> r.x
|
||
|
3
|
||
|
>>> r.set(x=2)
|
||
|
ARecord(x=2)
|
||
|
>>> r.set(y=2)
|
||
|
Traceback (most recent call last):
|
||
|
AttributeError: 'y' is not among the specified fields for ARecord
|
||
|
|
||
|
Type information
|
||
|
****************
|
||
|
It is possible to add type information to the record to enforce type checks. Multiple allowed types can be specified
|
||
|
by providing an iterable of types.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> class BRecord(PRecord):
|
||
|
... x = field(type=int)
|
||
|
... y = field(type=(int, type(None)))
|
||
|
...
|
||
|
>>> BRecord(x=3, y=None)
|
||
|
BRecord(y=None, x=3)
|
||
|
>>> BRecord(x=3.0)
|
||
|
Traceback (most recent call last):
|
||
|
PTypeError: Invalid type for field BRecord.x, was float
|
||
|
|
||
|
|
||
|
Custom types (classes) that are iterable should be wrapped in a tuple to prevent their
|
||
|
members being added to the set of valid types. Although Enums in particular are now
|
||
|
supported without wrapping, see #83 for more information.
|
||
|
|
||
|
Mandatory fields
|
||
|
****************
|
||
|
Fields are not mandatory by default but can be specified as such. If fields are missing an
|
||
|
*InvariantException* will be thrown which contains information about the missing fields.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> from pyrsistent import InvariantException
|
||
|
>>> class CRecord(PRecord):
|
||
|
... x = field(mandatory=True)
|
||
|
...
|
||
|
>>> r = CRecord(x=3)
|
||
|
>>> try:
|
||
|
... r.discard('x')
|
||
|
... except InvariantException as e:
|
||
|
... print(e.missing_fields)
|
||
|
...
|
||
|
('CRecord.x',)
|
||
|
|
||
|
Invariants
|
||
|
**********
|
||
|
It is possible to add invariants that must hold when evolving the record. Invariants can be
|
||
|
specified on both field and record level. If invariants fail an *InvariantException* will be
|
||
|
thrown which contains information about the failing invariants. An invariant function should
|
||
|
return a tuple consisting of a boolean that tells if the invariant holds or not and an object
|
||
|
describing the invariant. This object can later be used to identify which invariant that failed.
|
||
|
|
||
|
The global invariant function is only executed if all field invariants hold.
|
||
|
|
||
|
Global invariants are inherited to subclasses.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> class RestrictedVector(PRecord):
|
||
|
... __invariant__ = lambda r: (r.y >= r.x, 'x larger than y')
|
||
|
... x = field(invariant=lambda x: (x > 0, 'x negative'))
|
||
|
... y = field(invariant=lambda y: (y > 0, 'y negative'))
|
||
|
...
|
||
|
>>> r = RestrictedVector(y=3, x=2)
|
||
|
>>> try:
|
||
|
... r.set(x=-1, y=-2)
|
||
|
... except InvariantException as e:
|
||
|
... print(e.invariant_errors)
|
||
|
...
|
||
|
('y negative', 'x negative')
|
||
|
>>> try:
|
||
|
... r.set(x=2, y=1)
|
||
|
... except InvariantException as e:
|
||
|
... print(e.invariant_errors)
|
||
|
...
|
||
|
('x larger than y',)
|
||
|
|
||
|
Invariants may also contain multiple assertions. For those cases the invariant function should
|
||
|
return a tuple of invariant tuples as described above. This structure is reflected in the
|
||
|
invariant_errors attribute of the exception which will contain tuples with data from all failed
|
||
|
invariants. Eg:
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> class EvenX(PRecord):
|
||
|
... x = field(invariant=lambda x: ((x > 0, 'x negative'), (x % 2 == 0, 'x odd')))
|
||
|
...
|
||
|
>>> try:
|
||
|
... EvenX(x=-1)
|
||
|
... except InvariantException as e:
|
||
|
... print(e.invariant_errors)
|
||
|
...
|
||
|
(('x negative', 'x odd'),)
|
||
|
|
||
|
|
||
|
Factories
|
||
|
*********
|
||
|
It's possible to specify factory functions for fields. The factory function receives whatever
|
||
|
is supplied as field value and the actual returned by the factory is assigned to the field
|
||
|
given that any type and invariant checks hold.
|
||
|
PRecords have a default factory specified as a static function on the class, create(). It takes
|
||
|
a *Mapping* as argument and returns an instance of the specific record.
|
||
|
If a record has fields of type PRecord the create() method of that record will
|
||
|
be called to create the "sub record" if no factory has explicitly been specified to override
|
||
|
this behaviour.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> class DRecord(PRecord):
|
||
|
... x = field(factory=int)
|
||
|
...
|
||
|
>>> class ERecord(PRecord):
|
||
|
... d = field(type=DRecord)
|
||
|
...
|
||
|
>>> ERecord.create({'d': {'x': '1'}})
|
||
|
ERecord(d=DRecord(x=1))
|
||
|
|
||
|
Collection fields
|
||
|
*****************
|
||
|
It is also possible to have fields with ``pyrsistent`` collections.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> from pyrsistent import pset_field, pmap_field, pvector_field
|
||
|
>>> class MultiRecord(PRecord):
|
||
|
... set_of_ints = pset_field(int)
|
||
|
... map_int_to_str = pmap_field(int, str)
|
||
|
... vector_of_strs = pvector_field(str)
|
||
|
...
|
||
|
|
||
|
Serialization
|
||
|
*************
|
||
|
PRecords support serialization back to dicts. Default serialization will take keys and values
|
||
|
"as is" and output them into a dict. It is possible to specify custom serialization functions
|
||
|
to take care of fields that require special treatment.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> from datetime import date
|
||
|
>>> class Person(PRecord):
|
||
|
... name = field(type=unicode)
|
||
|
... birth_date = field(type=date,
|
||
|
... serializer=lambda format, d: d.strftime(format['date']))
|
||
|
...
|
||
|
>>> john = Person(name=u'John', birth_date=date(1985, 10, 21))
|
||
|
>>> john.serialize({'date': '%Y-%m-%d'})
|
||
|
{'birth_date': '1985-10-21', 'name': u'John'}
|
||
|
|
||
|
|
||
|
.. _instar: https://github.com/boxed/instar/
|
||
|
|
||
|
.. _PClass:
|
||
|
|
||
|
PClass
|
||
|
~~~~~~
|
||
|
A PClass is a python class with a fixed set of specified fields. PClasses are declared as python classes inheriting
|
||
|
from PClass. It is defined the same way that PRecords are and behaves like a PRecord in all aspects except that it
|
||
|
is not a PMap and hence not a collection but rather a plain Python object.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> from pyrsistent import PClass, field
|
||
|
>>> class AClass(PClass):
|
||
|
... x = field()
|
||
|
...
|
||
|
>>> a = AClass(x=3)
|
||
|
>>> a
|
||
|
AClass(x=3)
|
||
|
>>> a.x
|
||
|
3
|
||
|
|
||
|
|
||
|
Checked collections
|
||
|
~~~~~~~~~~~~~~~~~~~
|
||
|
Checked collections currently come in three flavors: CheckedPVector, CheckedPMap and CheckedPSet.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> from pyrsistent import CheckedPVector, CheckedPMap, CheckedPSet, thaw
|
||
|
>>> class Positives(CheckedPSet):
|
||
|
... __type__ = (long, int)
|
||
|
... __invariant__ = lambda n: (n >= 0, 'Negative')
|
||
|
...
|
||
|
>>> class Lottery(PRecord):
|
||
|
... name = field(type=str)
|
||
|
... numbers = field(type=Positives, invariant=lambda p: (len(p) > 0, 'No numbers'))
|
||
|
...
|
||
|
>>> class Lotteries(CheckedPVector):
|
||
|
... __type__ = Lottery
|
||
|
...
|
||
|
>>> class LotteriesByDate(CheckedPMap):
|
||
|
... __key_type__ = date
|
||
|
... __value_type__ = Lotteries
|
||
|
...
|
||
|
>>> lotteries = LotteriesByDate.create({date(2015, 2, 15): [{'name': 'SuperLotto', 'numbers': {1, 2, 3}},
|
||
|
... {'name': 'MegaLotto', 'numbers': {4, 5, 6}}],
|
||
|
... date(2015, 2, 16): [{'name': 'SuperLotto', 'numbers': {3, 2, 1}},
|
||
|
... {'name': 'MegaLotto', 'numbers': {6, 5, 4}}]})
|
||
|
>>> lotteries
|
||
|
LotteriesByDate({datetime.date(2015, 2, 15): Lotteries([Lottery(numbers=Positives([1, 2, 3]), name='SuperLotto'), Lottery(numbers=Positives([4, 5, 6]), name='MegaLotto')]), datetime.date(2015, 2, 16): Lotteries([Lottery(numbers=Positives([1, 2, 3]), name='SuperLotto'), Lottery(numbers=Positives([4, 5, 6]), name='MegaLotto')])})
|
||
|
|
||
|
# The checked versions support all operations that the corresponding
|
||
|
# unchecked types do
|
||
|
>>> lottery_0215 = lotteries[date(2015, 2, 15)]
|
||
|
>>> lottery_0215.transform([0, 'name'], 'SuperDuperLotto')
|
||
|
Lotteries([Lottery(numbers=Positives([1, 2, 3]), name='SuperDuperLotto'), Lottery(numbers=Positives([4, 5, 6]), name='MegaLotto')])
|
||
|
|
||
|
# But also makes asserts that types and invariants hold
|
||
|
>>> lottery_0215.transform([0, 'name'], 999)
|
||
|
Traceback (most recent call last):
|
||
|
PTypeError: Invalid type for field Lottery.name, was int
|
||
|
|
||
|
>>> lottery_0215.transform([0, 'numbers'], set())
|
||
|
Traceback (most recent call last):
|
||
|
InvariantException: Field invariant failed
|
||
|
|
||
|
# They can be converted back to python built ins with either thaw()
|
||
|
# or serialize() (which provides possibilities to customize serialization)
|
||
|
>>> thaw(lottery_0215)
|
||
|
[{'numbers': set([1, 2, 3]), 'name': 'SuperLotto'}, {'numbers': set([4, 5, 6]), 'name': 'MegaLotto'}]
|
||
|
>>> lottery_0215.serialize()
|
||
|
[{'numbers': set([1, 2, 3]), 'name': 'SuperLotto'}, {'numbers': set([4, 5, 6]), 'name': 'MegaLotto'}]
|
||
|
|
||
|
.. _transformations:
|
||
|
|
||
|
Transformations
|
||
|
~~~~~~~~~~~~~~~
|
||
|
Transformations are inspired by the cool library instar_ for Clojure. They let you evolve PMaps and PVectors
|
||
|
with arbitrarily deep/complex nesting using simple syntax and flexible matching syntax.
|
||
|
|
||
|
The first argument to transformation is the path that points out the value to transform. The
|
||
|
second is the transformation to perform. If the transformation is callable it will be applied
|
||
|
to the value(s) matching the path. The path may also contain callables. In that case they are
|
||
|
treated as matchers. If the matcher returns True for a specific key it is considered for transformation.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
# Basic examples
|
||
|
>>> from pyrsistent import inc, freeze, thaw, rex, ny, discard
|
||
|
>>> v1 = freeze([1, 2, 3, 4, 5])
|
||
|
>>> v1.transform([2], inc)
|
||
|
pvector([1, 2, 4, 4, 5])
|
||
|
>>> v1.transform([lambda ix: 0 < ix < 4], 8)
|
||
|
pvector([1, 8, 8, 8, 5])
|
||
|
>>> v1.transform([lambda ix, v: ix == 0 or v == 5], 0)
|
||
|
pvector([0, 2, 3, 4, 0])
|
||
|
|
||
|
# The (a)ny matcher can be used to match anything
|
||
|
>>> v1.transform([ny], 8)
|
||
|
pvector([8, 8, 8, 8, 8])
|
||
|
|
||
|
# Regular expressions can be used for matching
|
||
|
>>> scores = freeze({'John': 12, 'Joseph': 34, 'Sara': 23})
|
||
|
>>> scores.transform([rex('^Jo')], 0)
|
||
|
pmap({'Joseph': 0, 'Sara': 23, 'John': 0})
|
||
|
|
||
|
# Transformations can be done on arbitrarily deep structures
|
||
|
>>> news_paper = freeze({'articles': [{'author': 'Sara', 'content': 'A short article'},
|
||
|
... {'author': 'Steve', 'content': 'A slightly longer article'}],
|
||
|
... 'weather': {'temperature': '11C', 'wind': '5m/s'}})
|
||
|
>>> short_news = news_paper.transform(['articles', ny, 'content'], lambda c: c[:25] + '...' if len(c) > 25 else c)
|
||
|
>>> very_short_news = news_paper.transform(['articles', ny, 'content'], lambda c: c[:15] + '...' if len(c) > 15 else c)
|
||
|
>>> very_short_news.articles[0].content
|
||
|
'A short article'
|
||
|
>>> very_short_news.articles[1].content
|
||
|
'A slightly long...'
|
||
|
|
||
|
# When nothing has been transformed the original data structure is kept
|
||
|
>>> short_news is news_paper
|
||
|
True
|
||
|
>>> very_short_news is news_paper
|
||
|
False
|
||
|
>>> very_short_news.articles[0] is news_paper.articles[0]
|
||
|
True
|
||
|
|
||
|
# There is a special transformation that can be used to discard elements. Also
|
||
|
# multiple transformations can be applied in one call
|
||
|
>>> thaw(news_paper.transform(['weather'], discard, ['articles', ny, 'content'], discard))
|
||
|
{'articles': [{'author': 'Sara'}, {'author': 'Steve'}]}
|
||
|
|
||
|
Evolvers
|
||
|
~~~~~~~~
|
||
|
PVector, PMap and PSet all have support for a concept dubbed *evolvers*. An evolver acts like a mutable
|
||
|
view of the underlying persistent data structure with "transaction like" semantics. No updates of the original
|
||
|
data structure is ever performed, it is still fully immutable.
|
||
|
|
||
|
The evolvers have a very limited API by design to discourage excessive, and inappropriate, usage as that would
|
||
|
take us down the mutable road. In principle only basic mutation and element access functions are supported.
|
||
|
Check out the documentation_ of each data structure for specific examples.
|
||
|
|
||
|
Examples of when you may want to use an evolver instead of working directly with the data structure include:
|
||
|
|
||
|
* Multiple updates are done to the same data structure and the intermediate results are of no
|
||
|
interest. In this case using an evolver may be a more efficient and easier to work with.
|
||
|
* You need to pass a vector into a legacy function or a function that you have no control
|
||
|
over which performs in place mutations. In this case pass an evolver instance
|
||
|
instead and then create a new pvector from the evolver once the function returns.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> from pyrsistent import v
|
||
|
|
||
|
# In place mutation as when working with the built in counterpart
|
||
|
>>> v1 = v(1, 2, 3)
|
||
|
>>> e = v1.evolver()
|
||
|
>>> e[1] = 22
|
||
|
>>> e = e.append(4)
|
||
|
>>> e = e.extend([5, 6])
|
||
|
>>> e[5] += 1
|
||
|
>>> len(e)
|
||
|
6
|
||
|
|
||
|
# The evolver is considered *dirty* when it contains changes compared to the underlying vector
|
||
|
>>> e.is_dirty()
|
||
|
True
|
||
|
|
||
|
# But the underlying pvector still remains untouched
|
||
|
>>> v1
|
||
|
pvector([1, 2, 3])
|
||
|
|
||
|
# Once satisfied with the updates you can produce a new pvector containing the updates.
|
||
|
# The new pvector will share data with the original pvector in the same way that would have
|
||
|
# been done if only using operations on the pvector.
|
||
|
>>> v2 = e.persistent()
|
||
|
>>> v2
|
||
|
pvector([1, 22, 3, 4, 5, 7])
|
||
|
|
||
|
# The evolver is now no longer considered *dirty* as it contains no differences compared to the
|
||
|
# pvector just produced.
|
||
|
>>> e.is_dirty()
|
||
|
False
|
||
|
|
||
|
# You may continue to work with the same evolver without affecting the content of v2
|
||
|
>>> e[0] = 11
|
||
|
|
||
|
# Or create a new evolver from v2. The two evolvers can be updated independently but will both
|
||
|
# share data with v2 where possible.
|
||
|
>>> e2 = v2.evolver()
|
||
|
>>> e2[0] = 1111
|
||
|
>>> e.persistent()
|
||
|
pvector([11, 22, 3, 4, 5, 7])
|
||
|
>>> e2.persistent()
|
||
|
pvector([1111, 22, 3, 4, 5, 7])
|
||
|
|
||
|
.. _freeze:
|
||
|
.. _thaw:
|
||
|
|
||
|
freeze and thaw
|
||
|
~~~~~~~~~~~~~~~
|
||
|
These functions are great when your cozy immutable world has to interact with the evil mutable world outside.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> from pyrsistent import freeze, thaw, v, m
|
||
|
>>> freeze([1, {'a': 3}])
|
||
|
pvector([1, pmap({'a': 3})])
|
||
|
>>> thaw(v(1, m(a=3)))
|
||
|
[1, {'a': 3}]
|
||
|
|
||
|
By default, freeze will also recursively convert values inside PVectors and PMaps. This behaviour can be changed by providing freeze with the flag strict=False.
|
||
|
|
||
|
.. code:: python
|
||
|
|
||
|
>>> from pyrsistent import freeze, v, m
|
||
|
>>> freeze(v(1, v(2, [3])))
|
||
|
pvector([1, pvector([2, pvector([3])])])
|
||
|
>>> freeze(v(1, v(2, [3])), strict=False)
|
||
|
pvector([1, pvector([2, [3]])])
|
||
|
>>> freeze(m(a=m(b={'c': 1})))
|
||
|
pmap({'a': pmap({'b': pmap({'c': 1})})})
|
||
|
>>> freeze(m(a=m(b={'c': 1})), strict=False)
|
||
|
pmap({'a': pmap({'b': {'c': 1}})})
|
||
|
|
||
|
In this regard, thaw operates as the inverse of freeze so will thaw values inside native data structures unless passed the strict=False flag.
|
||
|
|
||
|
|
||
|
Compatibility
|
||
|
-------------
|
||
|
|
||
|
Pyrsistent is developed and tested on Python 3.7+ and PyPy3.
|
||
|
|
||
|
Performance
|
||
|
-----------
|
||
|
|
||
|
Pyrsistent is developed with performance in mind. Still, while some operations are nearly on par with their built in,
|
||
|
mutable, counterparts in terms of speed, other operations are slower. In the cases where attempts at
|
||
|
optimizations have been done, speed has generally been valued over space.
|
||
|
|
||
|
Pyrsistent comes with two API compatible flavors of PVector (on which PMap and PSet are based), one pure Python
|
||
|
implementation and one implemented as a C extension. The latter generally being 2 - 20 times faster than the former.
|
||
|
The C extension will be used automatically when possible.
|
||
|
|
||
|
The pure python implementation is fully PyPy compatible. Running it under PyPy speeds operations up considerably if
|
||
|
the structures are used heavily (if JITed), for some cases the performance is almost on par with the built in counterparts.
|
||
|
|
||
|
Type hints
|
||
|
----------
|
||
|
|
||
|
PEP 561 style type hints for use with mypy and various editors are available for most types and functions in pyrsistent.
|
||
|
|
||
|
Type classes for annotating your own code with pyrsistent types are also available under pyrsistent.typing.
|
||
|
|
||
|
Installation
|
||
|
------------
|
||
|
|
||
|
pip install pyrsistent
|
||
|
|
||
|
Documentation
|
||
|
-------------
|
||
|
|
||
|
Available at http://pyrsistent.readthedocs.org/
|
||
|
|
||
|
Brief presentation available at http://slides.com/tobiasgustafsson/immutability-and-python/
|
||
|
|
||
|
Contributors
|
||
|
------------
|
||
|
|
||
|
Tobias Gustafsson https://github.com/tobgu
|
||
|
|
||
|
Christopher Armstrong https://github.com/radix
|
||
|
|
||
|
Anders Hovmöller https://github.com/boxed
|
||
|
|
||
|
Itamar Turner-Trauring https://github.com/itamarst
|
||
|
|
||
|
Jonathan Lange https://github.com/jml
|
||
|
|
||
|
Richard Futrell https://github.com/Futrell
|
||
|
|
||
|
Jakob Hollenstein https://github.com/jkbjh
|
||
|
|
||
|
David Honour https://github.com/foolswood
|
||
|
|
||
|
David R. MacIver https://github.com/DRMacIver
|
||
|
|
||
|
Marcus Ewert https://github.com/sarum90
|
||
|
|
||
|
Jean-Paul Calderone https://github.com/exarkun
|
||
|
|
||
|
Douglas Treadwell https://github.com/douglas-treadwell
|
||
|
|
||
|
Travis Parker https://github.com/teepark
|
||
|
|
||
|
Julian Berman https://github.com/Julian
|
||
|
|
||
|
Dennis Tomas https://github.com/dtomas
|
||
|
|
||
|
Neil Vyas https://github.com/neilvyas
|
||
|
|
||
|
doozr https://github.com/doozr
|
||
|
|
||
|
Kamil Galuszka https://github.com/galuszkak
|
||
|
|
||
|
Tsuyoshi Hombashi https://github.com/thombashi
|
||
|
|
||
|
nattofriends https://github.com/nattofriends
|
||
|
|
||
|
agberk https://github.com/agberk
|
||
|
|
||
|
Waleed Khan https://github.com/arxanas
|
||
|
|
||
|
Jean-Louis Fuchs https://github.com/ganwell
|
||
|
|
||
|
Carlos Corbacho https://github.com/ccorbacho
|
||
|
|
||
|
Felix Yan https://github.com/felixonmars
|
||
|
|
||
|
benrg https://github.com/benrg
|
||
|
|
||
|
Jere Lahelma https://github.com/je-l
|
||
|
|
||
|
Max Taggart https://github.com/MaxTaggart
|
||
|
|
||
|
Vincent Philippon https://github.com/vphilippon
|
||
|
|
||
|
Semen Zhydenko https://github.com/ss18
|
||
|
|
||
|
Till Varoquaux https://github.com/till-varoquaux
|
||
|
|
||
|
Michal Kowalik https://github.com/michalvi
|
||
|
|
||
|
ossdev07 https://github.com/ossdev07
|
||
|
|
||
|
Kerry Olesen https://github.com/qhesz
|
||
|
|
||
|
johnthagen https://github.com/johnthagen
|
||
|
|
||
|
Bastien Vallet https://github.com/djailla
|
||
|
|
||
|
Ram Rachum https://github.com/cool-RR
|
||
|
|
||
|
Vincent Philippon https://github.com/vphilippon
|
||
|
|
||
|
Andrey Bienkowski https://github.com/hexagonrecursion
|
||
|
|
||
|
Ethan McCue https://github.com/bowbahdoe
|
||
|
|
||
|
Jason R. Coombs https://github.com/jaraco
|
||
|
|
||
|
Nathan https://github.com/ndowens
|
||
|
|
||
|
Geert Barentsen https://github.com/barentsen
|
||
|
|
||
|
phil-arh https://github.com/phil-arh
|
||
|
|
||
|
Tamás Nepusz https://github.com/ntamas
|
||
|
|
||
|
Hugo van Kemenade https://github.com/hugovk
|
||
|
|
||
|
Ben Beasley https://github.com/musicinmybrain
|
||
|
|
||
|
|
||
|
Contributing
|
||
|
------------
|
||
|
|
||
|
Want to contribute? That's great! If you experience problems please log them on GitHub. If you want to contribute code,
|
||
|
please fork the repository and submit a pull request.
|
||
|
|
||
|
Run tests
|
||
|
~~~~~~~~~
|
||
|
.. _tox: https://tox.readthedocs.io/en/latest/
|
||
|
|
||
|
Tests can be executed using tox_.
|
||
|
|
||
|
Install tox: ``pip install tox``
|
||
|
|
||
|
Run test for Python 3.8: ``tox -e py38``
|
||
|
|
||
|
Release
|
||
|
~~~~~~~
|
||
|
* `pip install -r requirements.txt`
|
||
|
* Update CHANGES.txt
|
||
|
* Update README.rst with any new contributors and potential info needed.
|
||
|
* Update _pyrsistent_version.py
|
||
|
* Commit and tag with new version: `git add -u . && git commit -m 'Prepare version vX.Y.Z' && git tag -a vX.Y.Z -m 'vX.Y.Z'`
|
||
|
* Push commit and tags: `git push && git push --tags`
|
||
|
* Build new release using Github actions
|
||
|
|
||
|
Project status
|
||
|
--------------
|
||
|
Pyrsistent can be considered stable and mature (who knows, there may even be a 1.0 some day :-)). The project is
|
||
|
maintained, bugs fixed, PRs reviewed and merged and new releases made. I currently do not have time for development
|
||
|
of new features or functionality which I don't have use for myself. I'm more than happy to take PRs for new
|
||
|
functionality though!
|
||
|
|
||
|
There are a bunch of issues marked with ``enhancement`` and ``help wanted`` that contain requests for new functionality
|
||
|
that would be nice to include. The level of difficulty and extend of the issues varies, please reach out to me if you're
|
||
|
interested in working on any of them.
|
||
|
|
||
|
If you feel that you have a grand master plan for where you would like Pyrsistent to go and have the time to put into
|
||
|
it please don't hesitate to discuss this with me and submit PRs for it. If all goes well I'd be more than happy to add
|
||
|
additional maintainers to the project!
|
||
|
|
||
|
|