### Running Tests with Tox

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Instructions for installing and running tests using the tox tool. Tox is used to automate testing in different Python environments.

```Shell
pip install tox
```

```Shell
tox -e py38
```

--------------------------------

### Running Tests with Tox

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Instructions for installing and running tests using the tox tool. Tox is used to automate testing in different Python environments.

```Shell
pip install tox
```

```Shell
tox -e py38
```

--------------------------------

### Invariant Exception Handling Example

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Provides an example of how invariant violations are caught and reported. It shows a try-except block catching an InvariantException and printing the specific invariant errors associated with the failed operation.

```python
from pyrsistent import InvariantException

>>> try:
...    EvenX(x=-1)
... except InvariantException as e:
...    print(e.invariant_errors)
...
(('x negative', 'x odd'),)
```

--------------------------------

### Release Process Commands

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Steps involved in releasing a new version of Pyrsistent. This includes installing dependencies, updating version files, committing changes, tagging, and pushing.

```Shell
pip install -r requirements.txt
```

```Shell
git add -u .
git commit -m 'Prepare version vX.Y.Z'
git tag -a vX.Y.Z -m 'vX.Y.Z'
```

```Shell
git push --follow-tags
```

--------------------------------

### Release Process Commands

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Steps involved in releasing a new version of Pyrsistent. This includes installing dependencies, updating version files, committing changes, tagging, and pushing.

```Shell
pip install -r requirements.txt
```

```Shell
git add -u .
git commit -m 'Prepare version vX.Y.Z'
git tag -a vX.Y.Z -m 'vX.Y.Z'
```

```Shell
git push --follow-tags
```

--------------------------------

### Invariant Exception Handling Example

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Provides an example of how invariant violations are caught and reported. It shows a try-except block catching an InvariantException and printing the specific invariant errors associated with the failed operation.

```python
from pyrsistent import InvariantException

>>> try:
...    EvenX(x=-1)
... except InvariantException as e:
...    print(e.invariant_errors)
...
(('x negative', 'x odd'),)
```

--------------------------------

### Freeze and Thaw Example

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Demonstrates the use of `freeze` and `thaw` functions to convert between mutable and immutable data structures. `freeze` converts Python lists and dicts into pyrsistent's PVector and PMap, respectively. `thaw` performs the inverse operation.

```python
from pyrsistent import freeze, thaw, v, m
freeze([1, {'a': 3}])
thaw(v(1, m(a=3)))
```

--------------------------------

### Freeze and Thaw Example

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Demonstrates the use of `freeze` and `thaw` functions to convert between mutable and immutable data structures. `freeze` converts Python lists and dicts into pyrsistent's PVector and PMap, respectively. `thaw` performs the inverse operation.

```python
from pyrsistent import freeze, thaw, v, m
freeze([1, {'a': 3}])
thaw(v(1, m(a=3)))
```

--------------------------------

### Python pyrsistent Transformations

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Demonstrates the use of the `transform` method on pyrsistent data structures (PMaps, PVectors) to modify values at specified paths. Supports index-based paths, callable matchers, regular expressions, and the `ny` (any) matcher for flexible data manipulation. Includes examples of deep transformations and discarding elements.

```python
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])
v1.transform([ny], 8)
# pvector([8, 8, 8, 8, 8])

scores = freeze({'John': 12, 'Joseph': 34, 'Sara': 23})
scores.transform([rex('^Jo')], 0)
# pmap({'Joseph': 0, 'Sara': 23, 'John': 0})

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)

# 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

thaw(news_paper.transform(['weather'], discard, ['articles', ny, 'content'], discard))
# {'articles': [{'author': 'Sara'}, {'author': 'Steve'}]}
```

--------------------------------

### UnicodeDecodeError Fix

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/changes.rst

Resolves a `UnicodeDecodeError` that occurred during `pip install` in environments with ASCII encoding as the default.

```APIDOC
pip install:
  Fixed UnicodeDecodeError in ASCII-default environments.
  Related: #66
```

--------------------------------

### UnicodeDecodeError Fix

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

Resolves a `UnicodeDecodeError` that occurred during `pip install` in environments with ASCII encoding as the default.

```APIDOC
pip install:
  Fixed UnicodeDecodeError in ASCII-default environments.
  Related: #66
```

--------------------------------

### Python pyrsistent Transformations

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Demonstrates the use of the `transform` method on pyrsistent data structures (PMaps, PVectors) to modify values at specified paths. Supports index-based paths, callable matchers, regular expressions, and the `ny` (any) matcher for flexible data manipulation. Includes examples of deep transformations and discarding elements.

```python
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])
v1.transform([ny], 8)
# pvector([8, 8, 8, 8, 8])

scores = freeze({'John': 12, 'Joseph': 34, 'Sara': 23})
scores.transform([rex('^Jo')], 0)
# pmap({'Joseph': 0, 'Sara': 23, 'John': 0})

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)

# 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

thaw(news_paper.transform(['weather'], discard, ['articles', ny, 'content'], discard))
# {'articles': [{'author': 'Sara'}, {'author': 'Steve'}]}
```

--------------------------------

### pmap Usage and Evolution

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Demonstrates the creation, access, transformation, and merging of persistent maps (pmap). Shows how updates create new versions without mutating the original map.

```python
from pyrsistent import pmap, m, v

# Basic pmap creation and access
>>> m1 = pmap({'a': 5, 'c': 3, 'b': 2})
>>> m1['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})

# Evolve by merging with other mappings
>>> m5 = m(a=1, b=2)
>>> 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
>>> m1.items()
pvector([('a', 5), ('c', 3), ('b', 2)])
>>> list(m1)
['a', 'c', 'b']
```

--------------------------------

### pmap Usage and Evolution

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Demonstrates the creation, access, transformation, and merging of persistent maps (pmap). Shows how updates create new versions without mutating the original map.

```python
from pyrsistent import pmap, m, v

# Basic pmap creation and access
>>> m1 = pmap({'a': 5, 'c': 3, 'b': 2})
>>> m1['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})

# Evolve by merging with other mappings
>>> m5 = m(a=1, b=2)
>>> 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
>>> m1.items()
pvector([('a', 5), ('c', 3), ('b', 2)])
>>> list(m1)
['a', 'c', 'b']
```

--------------------------------

### PMap/PVector/PSet Construction

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

Fixes construction from serialized objects for `pvector`, `pset`, and `pmap` fields.

```APIDOC
PMap/PVector/PSet Fields:
  Fixed construction from serialized objects.
  Related: #38
```

--------------------------------

### PMap/PVector/PSet Construction

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/changes.rst

Fixes construction from serialized objects for `pvector`, `pset`, and `pmap` fields.

```APIDOC
PMap/PVector/PSet Fields:
  Fixed construction from serialized objects.
  Related: #38
```

--------------------------------

### PRecord Declaration and Basic Usage

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Defines and uses a PRecord, a PMap with a fixed set of fields. Demonstrates field access, updates using `set`, and error handling for unknown fields.

```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
```

--------------------------------

### Checked Collections: Lottery and LotteriesByDate

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Illustrates the definition of checked collections: a Lottery PRecord using a CheckedPSet for numbers, a Lotteries CheckedPVector for Lottery objects, and a LotteriesByDate CheckedPMap mapping dates to Lotteries. This setup enforces type and invariant constraints throughout nested structures.

```python
from datetime import date
from pyrsistent import PRecord, field, CheckedPSet, CheckedPVector, CheckedPMap, 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')])})
```

--------------------------------

### Checked Collections: Lottery and LotteriesByDate

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Illustrates the definition of checked collections: a Lottery PRecord using a CheckedPSet for numbers, a Lotteries CheckedPVector for Lottery objects, and a LotteriesByDate CheckedPMap mapping dates to Lotteries. This setup enforces type and invariant constraints throughout nested structures.

```python
from datetime import date
from pyrsistent import PRecord, field, CheckedPSet, CheckedPVector, CheckedPMap, 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')])})
```

--------------------------------

### PSet Operations

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Illustrates the creation and manipulation of persistent sets (PSet). Shows how operations like add, remove, union, and intersection return new sets, preserving immutability.

```python
from pyrsistent import s

# No mutation of sets once created
>>> s1 = s(1, 2, 3, 2) # Duplicates are ignored
>>> 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) # Union
pse<ctrl61>t([1, 2, 3, 4, 5])
>>> s1 & s(3, 4, 5) # Intersection
pset([3])
>>> s1 < s2 # Subset check
True
>>> s1 < s(3, 4, 5) # Subset check
False
```

--------------------------------

### PVector Comparison

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

PVector now correctly compares against the built-in Python list type.

```APIDOC
PVector Comparison:
  Now compares against built-in list type.
  Related: #34
```

--------------------------------

### PRecord Field and Global Invariants

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Illustrates adding invariants to PRecord fields and the record itself. Shows how `InvariantException` is raised for failing invariants, detailing the specific errors.

```python
from pyrsistent import PRecord, field, InvariantException

>>> 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',)
```

--------------------------------

### PRecord Declaration and Basic Usage

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Defines and uses a PRecord, a PMap with a fixed set of fields. Demonstrates field access, updates using `set`, and error handling for unknown fields.

```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
```

--------------------------------

### PRecord Field Factories and Nested Creation

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Demonstrates how to specify factory functions for fields within a PRecord, such as converting input to integers. It also shows how PRecords handle nested PRecord creation automatically when a field is typed as another PRecord and no explicit factory is provided.

```python
from pyrsistent import PRecord, field

>>> class DRecord(PRecord):
...     x = field(factory=int)
...
>>> class ERecord(PRecord):
...     d = field(type=DRecord)
...
>>> ERecord.create({'d': {'x': '1'}})
ERecord(d=DRecord(x=1))
```

--------------------------------

### PMap and PVector Method Changes

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/changes.rst

PMap and PVector methods `values()`, `keys()`, and `items()` now return PVectors instead of Python lists. Ordering is explicitly disallowed for PMap and PBag.

```APIDOC
PMap:
  values(), keys(), items(): Now return PVectors.
  Ordering: Explicitly disallowed.

PVector:
  values(), keys(), items(): Now return PVectors.

Related: #37, #39
```

--------------------------------

### Serialization and Pickling

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

Enables multi-level serialization for checked types and supports pickling of PClasses and PRecords when using `pmap_field`, `pvector_field`, and `pset_field`.

```APIDOC
Serialization:
  Multi-level serialization for checked types.
  Related: v0.9.1

Pickling:
  Supports pickling of PClasses and PRecords using pmap_field, pvector_field, and pset_field.
  Related: #57
```

--------------------------------

### PSet Operations

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Illustrates the creation and manipulation of persistent sets (PSet). Shows how operations like add, remove, union, and intersection return new sets, preserving immutability.

```python
from pyrsistent import s

# No mutation of sets once created
>>> s1 = s(1, 2, 3, 2) # Duplicates are ignored
>>> 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) # Union
pse<ctrl61>t([1, 2, 3, 4, 5])
>>> s1 & s(3, 4, 5) # Intersection
pset([3])
>>> s1 < s2 # Subset check
True
>>> s1 < s(3, 4, 5) # Subset check
False
```

--------------------------------

### PVector and PMap Update Methods

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

Introduces the deprecation of `set_in()` for PVector and PMap, recommending the use of `transform()` instead. `set_in()` has been updated to use `transform()` internally, potentially altering behavior in some edge cases.

```python
from pyrsistent import pvector, pmap

# Deprecated usage
# old_vector = pvector([1, 2, 3])
# new_vector = old_vector.set_in([1], 99)

# Recommended usage
old_vector = pvector([1, 2, 3])
new_vector = old_vector.transform([1], 99)

old_map = pmap({'a': 1, 'b': 2})
new_map = old_map.transform(['b'], 99)

```

--------------------------------

### PVector and PMap Update Methods

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/changes.rst

Introduces the deprecation of `set_in()` for PVector and PMap, recommending the use of `transform()` instead. `set_in()` has been updated to use `transform()` internally, potentially altering behavior in some edge cases.

```python
from pyrsistent import pvector, pmap

# Deprecated usage
# old_vector = pvector([1, 2, 3])
# new_vector = old_vector.set_in([1], 99)

# Recommended usage
old_vector = pvector([1, 2, 3])
new_vector = old_vector.transform([1], 99)

old_map = pmap({'a': 1, 'b': 2})
new_map = old_map.transform(['b'], 99)

```

--------------------------------

### PMap and PVector Method Changes

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

PMap and PVector methods `values()`, `keys()`, and `items()` now return PVectors instead of Python lists. Ordering is explicitly disallowed for PMap and PBag.

```APIDOC
PMap:
  values(), keys(), items(): Now return PVectors.
  Ordering: Explicitly disallowed.

PVector:
  values(), keys(), items(): Now return PVectors.

Related: #37, #39
```

--------------------------------

### Serialization and Pickling

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/changes.rst

Enables multi-level serialization for checked types and supports pickling of PClasses and PRecords when using `pmap_field`, `pvector_field`, and `pset_field`.

```APIDOC
Serialization:
  Multi-level serialization for checked types.
  Related: v0.9.1

Pickling:
  Supports pickling of PClasses and PRecords using pmap_field, pvector_field, and pset_field.
  Related: #57
```

--------------------------------

### PRecord Field and Global Invariants

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Illustrates adding invariants to PRecord fields and the record itself. Shows how `InvariantException` is raised for failing invariants, detailing the specific errors.

```python
from pyrsistent import PRecord, field, InvariantException

>>> 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',)
```

--------------------------------

### PVector Comparison

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/changes.rst

PVector now correctly compares against the built-in Python list type.

```APIDOC
PVector Comparison:
  Now compares against built-in list type.
  Related: #34
```

--------------------------------

### PClass and PRecord Field Creation

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

Introduces convenience functions `pvector_field`, `pmap_field`, and `pset_field` for creating fields in PRecord and PClass that enforce checked collections. Also notes the public availability of `PClassMeta` for subclassing.

```APIDOC
Field Creation for Checked Collections:
  pvector_field()
  pmap_field()
  pset_field()
    Used to create fields for PRecord/PClass.
    Related: #26, #36

PClassMeta:
  Made public for friendlier subclassing.
```

--------------------------------

### PRecord Field Factories and Nested Creation

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Demonstrates how to specify factory functions for fields within a PRecord, such as converting input to integers. It also shows how PRecords handle nested PRecord creation automatically when a field is typed as another PRecord and no explicit factory is provided.

```python
from pyrsistent import PRecord, field

>>> class DRecord(PRecord):
...     x = field(factory=int)
...
>>> class ERecord(PRecord):
...     d = field(type=DRecord)
...
>>> ERecord.create({'d': {'x': '1'}})
ERecord(d=DRecord(x=1))
```

--------------------------------

### PClass and PRecord Field Creation

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/changes.rst

Introduces convenience functions `pvector_field`, `pmap_field`, and `pset_field` for creating fields in PRecord and PClass that enforce checked collections. Also notes the public availability of `PClassMeta` for subclassing.

```APIDOC
Field Creation for Checked Collections:
  pvector_field()
  pmap_field()
  pset_field()
    Used to create fields for PRecord/PClass.
    Related: #26, #36

PClassMeta:
  Made public for friendlier subclassing.
```

--------------------------------

### PRecord Serialization with Custom Functions

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Shows how to implement custom serialization for PRecord fields, particularly for types like datetime.date. A serializer function is defined to format the date into a string based on a provided format dictionary, enabling flexible data output.

```python
from datetime import date
from pyrsistent import PRecord, field

>>> 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'}
```

--------------------------------

### PVectorEvolver Delete Support

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/changes.rst

Provides complete support for the `delete` operation on the C-implementation of `PVectorEvolver`.

```APIDOC
PVectorEvolver:
  Complete support for delete operation on C-implementation.
  Related: #42
```

--------------------------------

### PRecord Serialization with Custom Functions

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Shows how to implement custom serialization for PRecord fields, particularly for types like datetime.date. A serializer function is defined to format the date into a string based on a provided format dictionary, enabling flexible data output.

```python
from datetime import date
from pyrsistent import PRecord, field

>>> 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'}
```

--------------------------------

### Type Error Handling and Support

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

Enhances type error reporting from checked types for more informative messages. Adds support for multiple optional types and renames `PRecordTypeError` to `PTypeError`.

```APIDOC
Type Errors:
  More informative messages from checked types.
  Related: #30

Optional Types:
  Support for multiple optional types.
  Related: #28

Exception Renaming:
  PRecordTypeError -> PTypeError
    Also raised by PClass.
```

--------------------------------

### Type Error Handling and Support

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/changes.rst

Enhances type error reporting from checked types for more informative messages. Adds support for multiple optional types and renames `PRecordTypeError` to `PTypeError`.

```APIDOC
Type Errors:
  More informative messages from checked types.
  Related: #30

Optional Types:
  Support for multiple optional types.
  Related: #28

Exception Renaming:
  PRecordTypeError -> PTypeError
    Also raised by PClass.
```

--------------------------------

### Weak References

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

Enables the creation of weak references to all collection types within the library.

```APIDOC
Weak References:
  Possible to create for all collection types.
  Related: #58
```

--------------------------------

### PVectorEvolver Delete Support

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

Provides complete support for the `delete` operation on the C-implementation of `PVectorEvolver`.

```APIDOC
PVectorEvolver:
  Complete support for delete operation on C-implementation.
  Related: #42
```

--------------------------------

### PMap and PVector Update/Merge Methods

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

The methods `merge()` and `merge_with()` on PMap have been renamed to `update()` and `update_with()` respectively. The older names are kept for compatibility but are marked for removal in version 1.0.

```python
from pyrsistent import pmap

map1 = pmap({'a': 1, 'b': 2})
map2 = pmap({'b': 3, 'c': 4})

# Using new names
updated_map = map1.update(map2)
print(f"Updated map: {updated_map}")

# Using old names (deprecated)
# merged_map = map1.merge(map2)
# print(f"Merged map: {merged_map}")

```

--------------------------------

### PRecord Mandatory Fields and InvariantException

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Demonstrates how to define mandatory fields in a PRecord. Shows that attempting to discard a mandatory field raises an `InvariantException` with missing fields information.

```python
from pyrsistent import PRecord, field, 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',)
```

--------------------------------

### Python 3.2 Compatibility

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

Removes the test build for Python 3.2 from Travis CI, indicating that while compatibility is not broken, future efforts to maintain it will cease.

```APIDOC
Python 3.2:
  Removed test build from Travis CI.
  Future compatibility maintenance will cease.
```

--------------------------------

### Pyrsistent PVector: Immutable List Operations

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Demonstrates the creation and manipulation of Pyrsistent PVectors, which are immutable list-like collections. Operations like append and set return new vectors, leaving the original untouched. Supports random access, slicing, and iteration.

```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 and PSet Copy Functions

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

PMap and PSet now include a `copy()` function to mimic the interface of Python's built-in `dict` and `set`. These functions return a reference to `self` as the collections are already persistent.

```python
from pyrsistent import pmap, pset

my_pmap = pmap({'a': 1})
copied_pmap = my_pmap.copy()
print(f"Is copied_pmap the same object as my_pmap? {copied_pmap is my_pmap}")

my_pset = pset({1, 2})
copied_pset = my_pset.copy()
print(f"Is copied_pset the same object as my_pset? {copied_pset is my_pset}")

```

--------------------------------

### Weak References

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/changes.rst

Enables the creation of weak references to all collection types within the library.

```APIDOC
Weak References:
  Possible to create for all collection types.
  Related: #58
```

--------------------------------

### PMap and PSet Copy Functions

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/changes.rst

PMap and PSet now include a `copy()` function to mimic the interface of Python's built-in `dict` and `set`. These functions return a reference to `self` as the collections are already persistent.

```python
from pyrsistent import pmap, pset

my_pmap = pmap({'a': 1})
copied_pmap = my_pmap.copy()
print(f"Is copied_pmap the same object as my_pmap? {copied_pmap is my_pmap}")

my_pset = pset({1, 2})
copied_pset = my_pset.copy()
print(f"Is copied_pset the same object as my_pset? {copied_pset is my_pset}")

```

--------------------------------

### PRecord Mandatory Fields and InvariantException

Source: https://github.com/tobgu/pyrsistent/blob/master/README.rst

Demonstrates how to define mandatory fields in a PRecord. Shows that attempting to discard a mandatory field raises an `InvariantException` with missing fields information.

```python
from pyrsistent import PRecord, field, 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',)
```

--------------------------------

### Python 3.2 Compatibility

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/changes.rst

Removes the test build for Python 3.2 from Travis CI, indicating that while compatibility is not broken, future efforts to maintain it will cease.

```APIDOC
Python 3.2:
  Removed test build from Travis CI.
  Future compatibility maintenance will cease.
```

--------------------------------

### PMap Reallocation Fix

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

Addresses a bug causing potential element loss during PMap reallocation.

```APIDOC
PMap Reallocation:
  Fixed bug causing potential element loss.
  Related: v0.11.2
```

--------------------------------

### PMap and PVector Update/Merge Methods

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/changes.rst

The methods `merge()` and `merge_with()` on PMap have been renamed to `update()` and `update_with()` respectively. The older names are kept for compatibility but are marked for removal in version 1.0.

```python
from pyrsistent import pmap

map1 = pmap({'a': 1, 'b': 2})
map2 = pmap({'b': 3, 'c': 4})

# Using new names
updated_map = map1.update(map2)
print(f"Updated map: {updated_map}")

# Using old names (deprecated)
# merged_map = map1.merge(map2)
# print(f"Merged map: {merged_map}")

```

--------------------------------

### Pyrsistent PVector: Immutable List Operations

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Demonstrates the creation and manipulation of Pyrsistent PVectors, which are immutable list-like collections. Operations like append and set return new vectors, leaving the original untouched. Supports random access, slicing, and iteration.

```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])
```

--------------------------------

### Python pyrsistent Evolvers

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Explains the concept of 'evolvers' in pyrsistent, which act as mutable views for persistent data structures like PVector, PMap, and PSet. Evolvers allow for efficient batch updates with transaction-like semantics before committing changes to a new persistent structure, while the original remains immutable.

```python
from pyrsistent import v

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) is 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.
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
# new persistent structure it just created.
```

--------------------------------

### Pyrsistent PMap: Immutable Dictionary Operations

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Illustrates the usage of Pyrsistent PMaps, which are immutable dictionary-like collections adhering to the Mapping protocol. Similar to PVectors, modifications create new PMap instances instead of altering the original. Supports efficient key-value access and updates.

```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})
```

--------------------------------

### PRecord Multiple Invariant Assertions

Source: https://github.com/tobgu/pyrsistent/blob/master/docs/source/intro.rst

Demonstrates how to define multiple invariant assertions for a single PRecord field. Shows that the `invariant_errors` attribute will contain data from all failed invariants.

```python
from pyrsistent import PRecord, field

>>> class EvenX(PRecord):
...     x = field(invariant=lambda x: ((x > 0, 'x negative'), (x % 2 == 0, 'x odd')))
...
```

--------------------------------

### PVector Operations

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

Details the addition of `remove()` to PVector for removing elements and `delete()` for removing elements by index or range, noting that `delete()` performs a full copy without structural sharing.

```APIDOC
PVector:
  remove(element)
    Removes an element from the vector.

  delete(index | slice)
    Removes elements by index or range.
    Performs a full copy, no structural sharing.
    Related: #42
```

--------------------------------

### Pythonic Renaming: assoc/assoc_in, massoc

Source: https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt

Several methods have been renamed to be more Pythonic. `assoc()` is now `set()`, `assoc_in()` is now `set_in()`, and `massoc()` is now `mset()`. These changes were made for better alignment with Python conventions.

```python
from pyrsistent import pmap, pvector

# PMap renaming
my_pmap = pmap({'a': 1})
new_pmap = my_pmap.set('b', 2) # Formerly assoc('b', 2)
print(f"PMap after set: {new_pmap}")

# PVector renaming
my_pvector = pvector([1, 2])
new_pvector = my_pvector.set_in([1], 99) # Formerly assoc_in([1], 99)
print(f"PVector after set_in: {new_pvector}")

# PMap massoc renaming
# new_pmap_mset = my_pmap.mset({'c': 3, 'd': 4}) # Formerly massoc({'c': 3, 'd': 4})

```