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05-data-classes/README.asciidoc

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+== Record-like Structures

05-data-classes/cards.doctest

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+>>> from cards import Card
+>>> helen = Card('Q', 'hearts')
+>>> helen
+Card(rank='Q', suit='hearts')
+
+>>> cards = [Card(r, s) for s in Card.suits for r in Card.ranks]
+>>> cards[:3]
+[Card(rank='2', suit='spades'), Card(rank='3', suit='spades'), Card(rank='4', suit='spades')]
+>>> sorted(cards)[:3]
+[Card(rank='2', suit='clubs'), Card(rank='2', suit='diamonds'), Card(rank='2', suit='hearts')]
+
+>>> from cards_enum import Card, Suit, Rank
+>>> helen = Card('Q', 'hearts')
+>>> helen
+Card(rank='Q', suit='hearts')
+
+>>> cards = [Card(r, s) for s in Suit for r in Rank]
+>>> cards[:3]
+[Card(rank='2', suit='spades'), Card(rank='3', suit='spades'), Card(rank='4', suit='spades')]
+>>> sorted(cards)[:3]
+[Card(rank='2', suit='clubs'), Card(rank='2', suit='diamonds'), Card(rank='2', suit='hearts')]
+>>> for card in cards[12::13]: print(card)

05-data-classes/cards.py

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+from dataclasses import dataclass
+
+@dataclass(order=True)
+class Card:
+    rank: str
+    suit: str
+
+    ranks = [str(n) for n in range(2, 10)] + list('JQKA')
+    suits = 'spades diamonds clubs hearts'.split()

05-data-classes/cards_enum.py

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+from dataclasses import dataclass
+import enum
+
+Suit = enum.IntEnum('Suit', 'spades diamonds clubs hearts')
+Rank = enum.Enum('Rank', [str(n) for n in range(2, 10)] + list('JQKA'))
+
+@dataclass(order=True)
+class Card:
+    rank: Suit
+    suit: Rank
+
+    def __str__(self):
+        glyphs = [chr(x) for x in range(0x2660, 0x2664)]
+        return f'{self.rank} of {glyphs[self.suit-1]}'

05-data-classes/class/coordinates.py

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+"""
+``Coordinate``: a simple class with a custom ``__str__``::
+
+    >>> moscow = Coordinate(55.756, 37.617)
+    >>> print(moscow)  # doctest:+ELLIPSIS
+    <coordinates.Coordinate object at 0x...>
+"""
+
+# tag::COORDINATE[]
+class Coordinate:
+
+    def __init__(self, lat, lon):
+        self.lat = lat
+        self.lon = lon
+
+# end::COORDINATE[]

05-data-classes/dataclass/club.py

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+from dataclasses import dataclass, field
+
+
+@dataclass
+class ClubMember:
+
+    name: str
+    guests: list = field(default_factory=list)
+

05-data-classes/dataclass/club_generic.py

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+from dataclasses import dataclass, field
+
+@dataclass
+class ClubMember:
+    name: str
+    guests: list[str] = field(default_factory=list)  # <1>

05-data-classes/dataclass/club_wrong.py

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+from dataclasses import dataclass
+
+# tag::CLUBMEMBER[]
+@dataclass
+class ClubMember:
+
+    name: str
+    guests: list = []
+# end::CLUBMEMBER[]

05-data-classes/dataclass/coordinates.py

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+"""
+``Coordinate``: simple class decorated with ``dataclass`` and a custom ``__str__``::
+
+    >>> moscow = Coordinate(55.756, 37.617)
+    >>> print(moscow)
+    55.8°N, 37.6°E
+
+"""
+
+# tag::COORDINATE[]
+
+from dataclasses import dataclass
+
+@dataclass(frozen=True)
+class Coordinate:
+    lat: float
+    lon: float
+
+    def __str__(self):
+        ns = 'N' if self.lat >= 0 else 'S'
+        we = 'E' if self.lon >= 0 else 'W'
+        return f'{abs(self.lat):.1f}°{ns}, {abs(self.lon):.1f}°{we}'
+# end::COORDINATE[]

05-data-classes/dataclass/hackerclub.py

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+# tag::DOCTESTS[]
+"""
+``HackerClubMember`` objects accept an optional ``handle`` argument::
+
+    >>> anna = HackerClubMember('Anna Ravenscroft', handle='AnnaRaven')
+    >>> anna
+    HackerClubMember(name='Anna Ravenscroft', guests=[], handle='AnnaRaven')
+
+If ``handle`` is ommitted, it's set to the first part of the member's name::
+
+    >>> leo = HackerClubMember('Leo Rochael')
+    >>> leo
+    HackerClubMember(name='Leo Rochael', guests=[], handle='Leo')
+
+Members must have a unique handle. The following ``leo2`` will not be created,
+because its ``handle`` would be 'Leo', which was taken by ``leo``::
+
+    >>> leo2 = HackerClubMember('Leo DaVinci')
+    Traceback (most recent call last):
+      ...
+    ValueError: handle 'Leo' already exists.
+
+To fix, ``leo2`` must be created with an explicit ``handle``::
+
+    >>> leo2 = HackerClubMember('Leo DaVinci', handle='Neo')
+    >>> leo2
+    HackerClubMember(name='Leo DaVinci', guests=[], handle='Neo')
+"""
+# end::DOCTESTS[]
+
+# tag::HACKERCLUB[]
+from dataclasses import dataclass
+from club import ClubMember
+
+@dataclass
+class HackerClubMember(ClubMember):                         # <1>
+
+    all_handles = set()                                     # <2>
+
+    handle: str = ''                                        # <3>
+
+    def __post_init__(self):
+        cls = self.__class__                                # <4>
+        if self.handle == '':                               # <5>
+            self.handle = self.name.split()[0]
+        if self.handle in cls.all_handles:                  # <6>
+            msg = f'handle {self.handle!r} already exists.'
+            raise ValueError(msg)
+        cls.all_handles.add(self.handle)                    # <7>
+# end::HACKERCLUB[]

05-data-classes/dataclass/hackerclub_annotated.py

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+# tag::DOCTESTS[]
+"""
+``HackerClubMember`` objects can be created with a ``name`` and an optional ``handle``::
+
+    >>> anna = HackerClubMember('Anna Ravenscroft', handle='AnnaRaven')
+    >>> anna
+    HackerClubMember(name='Anna Ravenscroft', guests=[], handle='AnnaRaven')
+
+If ``handle`` is ommitted, it's set to the first part of the member's name::
+
+    >>> leo = HackerClubMember('Leo Rochael')
+    >>> leo
+    HackerClubMember(name='Leo Rochael', guests=[], handle='Leo')
+
+Members must have a unique handle. This ``leo2`` will not be created,
+because its ``handle`` would be 'Leo', which was taken by ``leo``::
+
+    >>> leo2 = HackerClubMember('Leo DaVinci')
+    Traceback (most recent call last):
+      ...
+    ValueError: handle 'Leo' already exists.
+
+To fix, ``leo2`` must be created with an explicit ``handle``::
+
+    >>> leo2 = HackerClubMember('Leo DaVinci', handle='Neo')
+    >>> leo2
+    HackerClubMember(name='Leo DaVinci', guests=[], handle='Neo')
+"""
+# end::DOCTESTS[]
+
+# tag::HACKERCLUB[]
+from dataclasses import dataclass
+from typing import ClassVar
+from club import ClubMember
+
+@dataclass
+class HackerClubMember(ClubMember):
+
+    all_handles: ClassVar[set[str]] = set()
+
+    handle: str = ''
+
+    def __post_init__(self):
+        cls = self.__class__
+        if self.handle == '':
+            self.handle = self.name.split()[0]
+        if self.handle in cls.all_handles:
+            msg = f'handle {self.handle!r} already exists.'
+            raise ValueError(msg)
+        cls.all_handles.add(self.handle)
+# end::HACKERCLUB[]

05-data-classes/dataclass/resource.py

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+"""
+Media resource description class with subset of the Dublin Core fields.
+
+Default field values:
+
+    >>> r = Resource('0')
+    >>> r  # doctest: +NORMALIZE_WHITESPACE
+    Resource(identifier='0', title='<untitled>', creators=[], date=None,
+    type=<ResourceType.BOOK: 1>, description='', language='', subjects=[])
+
+A complete resource record:
+# tag::DOCTEST[]
+
+    >>> description = 'Improving the design of existing code'
+    >>> book = Resource('978-0-13-475759-9', 'Refactoring, 2nd Edition',
+    ...     ['Martin Fowler', 'Kent Beck'], date(2018, 11, 19),
+    ...     ResourceType.BOOK, description, 'EN',
+    ...     ['computer programming', 'OOP'])
+    >>> book  # doctest: +NORMALIZE_WHITESPACE
+    Resource(identifier='978-0-13-475759-9', title='Refactoring, 2nd Edition',
+    creators=['Martin Fowler', 'Kent Beck'], date=datetime.date(2018, 11, 19),
+    type=<ResourceType.BOOK: 1>, description='Improving the design of existing code',
+    language='EN', subjects=['computer programming', 'OOP'])
+
+# end::DOCTEST[]
+"""
+
+# tag::DATACLASS[]
+from dataclasses import dataclass, field
+from typing import Optional
+from enum import Enum, auto
+from datetime import date
+
+
+class ResourceType(Enum):                              # <1>
+    BOOK = auto()
+    EBOOK = auto()
+    VIDEO = auto()
+
+
+@dataclass
+class Resource:
+    """Media resource description."""
+    identifier: str                                    # <2>
+    title: str = '<untitled>'                          # <3>
+    creators: list[str] = field(default_factory=list)
+    date: Optional[date] = None                        # <4>
+    type: ResourceType = ResourceType.BOOK             # <5>
+    description: str = ''
+    language: str = ''
+    subjects: list[str] = field(default_factory=list)
+# end::DATACLASS[]
+
+
+from typing import TypedDict
+
+
+class ResourceDict(TypedDict):
+    identifier: str
+    title: str
+    creators: list[str]
+    date: Optional[date]
+    type: ResourceType
+    description: str
+    language: str
+    subjects: list[str]
+
+
+if __name__ == '__main__':
+    r = Resource('0')
+    description = 'Improving the design of existing code'
+    book = Resource('978-0-13-475759-9', 'Refactoring, 2nd Edition',
+                    ['Martin Fowler', 'Kent Beck'], date(2018, 11, 19),
+                    ResourceType.BOOK, description,
+                    'EN', ['computer programming', 'OOP'])
+    print(book)
+    book_dict: ResourceDict = {
+        'identifier': '978-0-13-475759-9',
+        'title': 'Refactoring, 2nd Edition',
+        'creators': ['Martin Fowler', 'Kent Beck'],
+        'date': date(2018, 11, 19),
+        'type': ResourceType.BOOK,
+        'description': 'Improving the design of existing code',
+        'language': 'EN',
+        'subjects': ['computer programming', 'OOP']}
+    book2 = Resource(**book_dict)
+    print(book == book2)

05-data-classes/dataclass/resource_repr.py

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+"""
+Media resource description class with subset of the Dublin Core fields.
+
+Default field values:
+
+    >>> r = Resource('0')
+    >>> r  # doctest: +NORMALIZE_WHITESPACE
+    Resource(
+        identifier = '0',
+        title = '<untitled>',
+        creators = [],
+        date = None,
+        type = <ResourceType.BOOK: 1>,
+        description = '',
+        language = '',
+        subjects = [],
+    )
+
+A complete resource record:
+
+    >>> description = 'Improving the design of existing code'
+    >>> book = Resource('978-0-13-475759-9', 'Refactoring, 2nd Edition',
+    ...     ['Martin Fowler', 'Kent Beck'], date(2018, 11, 19),
+    ...     ResourceType.BOOK, description, 'EN',
+    ...     ['computer programming', 'OOP'])
+
+# tag::DOCTEST[]
+    >>> book  # doctest: +NORMALIZE_WHITESPACE
+    Resource(
+        identifier = '978-0-13-475759-9',
+        title = 'Refactoring, 2nd Edition',
+        creators = ['Martin Fowler', 'Kent Beck'],
+        date = datetime.date(2018, 11, 19),
+        type = <ResourceType.BOOK: 1>,
+        description = 'Improving the design of existing code',
+        language = 'EN',
+        subjects = ['computer programming', 'OOP'],
+    )
+
+# end::DOCTEST[]
+"""
+
+from dataclasses import dataclass, field, fields
+from typing import Optional, TypedDict
+from enum import Enum, auto
+from datetime import date
+
+
+class ResourceType(Enum):
+    BOOK = auto()
+    EBOOK = auto()
+    VIDEO = auto()
+
+
+@dataclass
+class Resource:
+    """Media resource description."""
+    identifier: str
+    title: str = '<untitled>'
+    creators: list[str] = field(default_factory=list)
+    date: Optional[date] = None
+    type: ResourceType = ResourceType.BOOK
+    description: str = ''
+    language: str = ''
+    subjects: list[str] = field(default_factory=list)
+
+# tag::REPR[]
+    def __repr__(self):
+        cls = self.__class__
+        cls_name = cls.__name__
+        indent = ' ' * 4
+        res = [f'{cls_name}(']                            # <1>
+        for f in fields(cls):                             # <2>
+            value = getattr(self, f.name)                 # <3>
+            res.append(f'{indent}{f.name} = {value!r},')  # <4>
+
+        res.append(')')                                   # <5>
+        return '\n'.join(res)                             # <6>
+# end::REPR[]
+
+
+class ResourceDict(TypedDict):
+    identifier: str
+    title: str
+    creators: list[str]
+    date: Optional[date]
+    type: ResourceType
+    description: str
+    language: str
+    subjects: list[str]
+
+
+if __name__ == '__main__':
+    r = Resource('0')
+    description = 'Improving the design of existing code'
+    book = Resource('978-0-13-475759-9', 'Refactoring, 2nd Edition',
+                    ['Martin Fowler', 'Kent Beck'], date(2018, 11, 19),
+                    ResourceType.BOOK, description,
+                    'EN', ['computer programming', 'OOP'])
+    print(book)
+    book_dict: ResourceDict = {
+        'identifier': '978-0-13-475759-9',
+        'title': 'Refactoring, 2nd Edition',
+        'creators': ['Martin Fowler', 'Kent Beck'],
+        'date': date(2018, 11, 19),
+        'type': ResourceType.BOOK,
+        'description': 'Improving the design of existing code',
+        'language': 'EN',
+        'subjects': ['computer programming', 'OOP']}
+    book2 = Resource(**book_dict)
+    print(book == book2)

05-data-classes/frenchdeck.doctest

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+>>> from frenchdeck import FrenchDeck, Card
+>>> beer_card = Card('7', 'diamonds')
+>>> beer_card
+Card(rank='7', suit='diamonds')
+>>> deck = FrenchDeck()
+>>> len(deck)
+52
+>>> deck[:3]
+[Card(rank='2', suit='spades'), Card(rank='3', suit='spades'), Card(rank='4', suit='spades')]
+>>> deck[12::13]
+[Card(rank='A', suit='spades'), Card(rank='A', suit='diamonds'), Card(rank='A', suit='clubs'), Card(rank='A', suit='hearts')]
+>>> Card('Q', 'hearts') in deck
+True
+>>> Card('Z', 'clubs') in deck
+False
+>>> for card in deck:  # doctest: +ELLIPSIS
+...   print(card)
+Card(rank='2', suit='spades')
+Card(rank='3', suit='spades')
+Card(rank='4', suit='spades')
+...
+>>> for card in reversed(deck):  # doctest: +ELLIPSIS
+...   print(card)
+Card(rank='A', suit='hearts')
+Card(rank='K', suit='hearts')
+Card(rank='Q', suit='hearts')
+...
+>>> for n, card in enumerate(deck, 1):  # doctest: +ELLIPSIS
+...   print(n, card)
+1 Card(rank='2', suit='spades')
+2 Card(rank='3', suit='spades')
+3 Card(rank='4', suit='spades')
+...
+
+Sort with *spades high* overall ranking
+
+# tag::SPADES_HIGH[]
+>>> Card.suit_values = dict(spades=3, hearts=2, diamonds=1, clubs=0)  # <1>
+>>> def spades_high(card):                                            # <2>
+...     rank_value = FrenchDeck.ranks.index(card.rank)                
+...     suit_value = card.suit_values[card.suit]
+...     return rank_value * len(card.suit_values) + suit_value
+...
+>>> Card.overall_rank = spades_high                                   # <3>
+>>> lowest_card = Card('2', 'clubs')
+>>> highest_card = Card('A', 'spades')
+>>> lowest_card.overall_rank()                                        # <4>
+0
+>>> highest_card.overall_rank()
+51
+
+# end::SPADES_HIGH[]
+
+
+>>> for card in sorted(deck, key=Card.overall_rank):  # doctest: +ELLIPSIS
+...      print(card)
+Card(rank='2', suit='clubs')
+Card(rank='2', suit='diamonds')
+Card(rank='2', suit='hearts')
+...
+Card(rank='A', suit='diamonds')
+Card(rank='A', suit='hearts')
+Card(rank='A', suit='spades')
+

05-data-classes/frenchdeck.py

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+import collections
+
+Card = collections.namedtuple('Card', ['rank', 'suit'])
+
+class FrenchDeck:
+    ranks = [str(n) for n in range(2, 11)] + list('JQKA')
+    suits = 'spades diamonds clubs hearts'.split()
+
+    def __init__(self):
+        self._cards = [Card(rank, suit) for suit in self.suits
+                                        for rank in self.ranks]
+
+    def __len__(self):
+        return len(self._cards)
+
+    def __getitem__(self, position):
+        return self._cards[position]

05-data-classes/match_cities.py

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+"""
+match_cities.py
+"""
+
+# tag::CITY[]
+import typing
+
+class City(typing.NamedTuple):
+    continent: str
+    name: str
+    country: str
+
+
+cities = [
+    City('Asia', 'Tokyo', 'JP'),
+    City('Asia', 'Delhi', 'IN'),
+    City('North America', 'Mexico City', 'MX'),
+    City('North America', 'New York', 'US'),
+    City('South America', 'São Paulo', 'BR'),
+]
+# end::CITY[]
+
+# tag::ASIA[]
+def match_asian_cities():
+    results = []
+    for city in cities:
+        match city:
+            case City(continent='Asia'):
+                results.append(city)
+    return results
+# end::ASIA[]
+
+# tag::ASIA_POSITIONAL[]
+def match_asian_cities_pos():
+    results = []
+    for city in cities:
+        match city:
+            case City('Asia'):
+                results.append(city)
+    return results
+# end::ASIA_POSITIONAL[]
+
+
+# tag::ASIA_COUNTRIES[]
+def match_asian_countries():
+    results = []
+    for city in cities:
+        match city:
+            case City(continent='Asia', country=cc):
+                results.append(cc)
+    return results
+# end::ASIA_COUNTRIES[]
+
+# tag::ASIA_COUNTRIES_POSITIONAL[]
+def match_asian_countries_pos():
+    results = []
+    for city in cities:
+        match city:
+            case City('Asia', _, country):
+                results.append(country)
+    return results
+# end::ASIA_COUNTRIES_POSITIONAL[]
+
+
+def match_india():
+    results = []
+    for city in cities:
+        match city:
+            case City(_, name, 'IN'):
+                results.append(name)
+    return results
+
+
+def match_brazil():
+    results = []
+    for city in cities:
+        match city:
+            case City(country='BR', name=name):
+                results.append(name)
+    return results
+
+
+
+def main():
+    tests = ((n, f) for n, f in globals().items() if n.startswith('match_'))
+
+    for name, func in tests:
+        print(f'{name:15}\t{func()}')
+
+
+if __name__ == '__main__':
+    main()

05-data-classes/meaning/demo_dc.py

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+from dataclasses import dataclass
+
+@dataclass
+class DemoDataClass:
+
+    a: int           # <1>
+    b: float = 1.1   # <2>
+    c = 'spam'       # <3>

05-data-classes/meaning/demo_nt.py

@@ -0,0 +1,7 @@
+import typing
+
+class DemoNTClass(typing.NamedTuple):
+
+    a: int           # <1>
+    b: float = 1.1   # <2>
+    c = 'spam'       # <3>

05-data-classes/meaning/demo_plain.py

@@ -0,0 +1,5 @@
+class DemoPlainClass:
+
+    a: int           # <1>
+    b: float = 1.1   # <2>
+    c = 'spam'       # <3>

05-data-classes/typing_namedtuple/coordinates.py

@@ -0,0 +1,22 @@
+"""
+``Coordinate``: a simple ``NamedTuple`` subclass with a custom ``__str__``::
+
+    >>> moscow = Coordinate(55.756, 37.617)
+    >>> print(moscow)
+    55.8°N, 37.6°E
+
+"""
+
+# tag::COORDINATE[]
+from typing import NamedTuple
+
+class Coordinate(NamedTuple):
+
+    lat: float
+    lon: float
+
+    def __str__(self):
+        ns = 'N' if self.lat >= 0 else 'S'
+        we = 'E' if self.lon >= 0 else 'W'
+        return f'{abs(self.lat):.1f}°{ns}, {abs(self.lon):.1f}°{we}'
+# end::COORDINATE[]

05-data-classes/typing_namedtuple/coordinates2.py

@@ -0,0 +1,20 @@
+"""
+``Coordinate``: a simple ``NamedTuple`` subclass
+
+This version has a field with a default value::
+
+    >>> moscow = Coordinate(55.756, 37.617)
+    >>> moscow
+    Coordinate(lat=55.756, lon=37.617, reference='WGS84')
+
+"""
+
+# tag::COORDINATE[]
+from typing import NamedTuple
+
+class Coordinate(NamedTuple):
+
+    lat: float                # <1>
+    lon: float
+    reference: str = 'WGS84'  # <2>
+# end::COORDINATE[]

05-data-classes/typing_namedtuple/nocheck_demo.py

@@ -0,0 +1,9 @@
+import typing
+
+class Coordinate(typing.NamedTuple):
+
+    lat: float
+    lon: float
+
+trash = Coordinate('Ni!', None)  # <1>
+print(trash)