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# `zoneinfo` — Suporte a fuso horário da IANA

Novo na versão 3.9.

The `zoneinfo` module provides a concrete time zone implementation to support the IANA time zone database as originally specified in PEP 615. By default, `zoneinfo` uses the system’s time zone data if available; if no system time zone data is available, the library will fall back to using the first-party tzdata package available on PyPI.

Ver também

Módulo: `datetime`

  Fornece os tipos `time` e `datetime` com os quais a classe `ZoneInfo` foi projetada para ser usada.

Package tzdata

  Pacote próprio mantido pelos desenvolvedores principais do CPython para fornecer dados de fuso horário via PyPI.

## Usando `ZoneInfo`

`ZoneInfo` é uma implementação concreta da classe base abstrata `datetime.tzinfo` e deve ser anexada a `tzinfo`, por meio do construtor, do método `datetime.replace` ou `datetime.astimezone`:

    >>> from zoneinfo import ZoneInfo
    >>> from datetime import datetime, timedelta

    >>> dt = datetime(2020, 10, 31, 12, tzinfo=ZoneInfo("America/Los_Angeles"))
    >>> print(dt)
    2020-10-31 12:00:00-07:00

    >>> dt.tzname()
    'PDT'

Datas e horas construídas dessa maneira são compatíveis com a aritmética de data e hora e lidam com transições de horário de verão sem intervenção adicional:

    >>> dt_add = dt + timedelta(days=1)

    >>> print(dt_add)
    2020-11-01 12:00:00-08:00

    >>> dt_add.tzname()
    'PST'

Esses fusos horários também oferecem suporte ao atributo `fold` introduzido em PEP 495. Durante transições de deslocamento que induzem horários ambíguos (como uma transição do horário de verão para o horário padrão), o deslocamento anterior à transição é usado quando `fold=0`, e o deslocamento posterior à transição é usado quando `fold=1`, por exemplo:

    >>> dt = datetime(2020, 11, 1, 1, tzinfo=ZoneInfo("America/Los_Angeles"))
    >>> print(dt)
    2020-11-01 01:00:00-07:00

    >>> print(dt.replace(fold=1))
    2020-11-01 01:00:00-08:00

Ao converter de outro fuso horário, a dobra será definida para o valor correto:

    >>> from datetime import timezone
    >>> LOS_ANGELES = ZoneInfo("America/Los_Angeles")
    >>> dt_utc = datetime(2020, 11, 1, 8, tzinfo=timezone.utc)

    >>> # Before the PDT -> PST transition
    >>> print(dt_utc.astimezone(LOS_ANGELES))
    2020-11-01 01:00:00-07:00

    >>> # After the PDT -> PST transition
    >>> print((dt_utc + timedelta(hours=1)).astimezone(LOS_ANGELES))
    2020-11-01 01:00:00-08:00

## Fontes de dados

The `zoneinfo` module does not directly provide time zone data, and instead pulls time zone information from the system time zone database or the first-party PyPI package tzdata, if available. Some systems, including notably Windows systems, do not have an IANA database available, and so for projects targeting cross-platform compatibility that require time zone data, it is recommended to declare a dependency on tzdata. If neither system data nor tzdata are available, all calls to `ZoneInfo` will raise `ZoneInfoNotFoundError`.

### Configurando as fontes de dados

Quando `ZoneInfo(key)` é chamado, o construtor primeiro pesquisa nos diretórios especificados em `TZPATH` por um arquivo que corresponda a `key` e, em caso de falha, procura uma correspondência no pacote tzdata. Esse comportamento pode ser configurado de três maneiras:

1. O padrão `TZPATH`, quando não especificado de outra forma, pode ser configurado em tempo de compilação.

2. `TZPATH` pode ser configurado usando uma variável de ambiente.

3. Em tempo de execução, o caminho de pesquisa pode ser manipulado usando a função `reset_tzpath()`.

#### Configuração em tempo de compilação

The default `TZPATH` includes several common deployment locations for the time zone database (except on Windows, where there are no “well-known” locations for time zone data). On POSIX systems, downstream distributors and those building Python from source who know where their system time zone data is deployed may change the default time zone path by specifying the compile-time option `TZPATH` (or, more likely, the `configure` flag `--with-tzpath`), which should be a string delimited by `os.pathsep`.

Em todas as plataformas, o valor configurado está disponível como a chave `TZPATH` em `sysconfig.get_config_var()`.

#### Configuração do ambiente

Ao inicializar `TZPATH` (no momento da importação ou sempre que `reset_tzpath()` for chamado sem argumentos), o módulo `zoneinfo` usará a variável de ambiente `PYTHONTZPATH`, se existir, para definir o caminho de pesquisa.

`PYTHONTZPATH`

  Esta é uma string separada por `os.pathsep` contendo o caminho de pesquisa de fuso horário a ser usado. Ela deve consistir apenas em caminhos absolutos, e não relativos. Componentes relativos especificados em `PYTHONTZPATH` não serão usados, mas, caso contrário, o comportamento quando um caminho relativo é especificado é definido pela implementação; o CPython levantará `InvalidTZPathWarning`, mas outras implementações podem ignorar silenciosamente o componente incorreto ou levantar uma exceção.

Para configurar o sistema para ignorar os dados do sistema e usar o pacote tzdata, defina `PYTHONTZPATH=""`.

#### Configuração em tempo de execução

O caminho de busca TZ também pode ser configurado em tempo de execução usando a função `reset_tzpath()`. Geralmente, essa não é uma operação aconselhável, embora seja razoável usá-la em funções de teste que exigem o uso de um caminho de fuso horário específico (ou que exijam a desativação do acesso aos fusos horários do sistema).

## A classe `ZoneInfo`

class `zoneinfo.``ZoneInfo`(key)

  Uma subclasse concreta de `datetime.tzinfo` que representa um fuso horário IANA especificado pela string `key`. Chamadas ao construtor primário sempre retornarão objetos que sejam idênticos em comparação; em outras palavras, exceto pela invalidação de cache via `ZoneInfo.clear_cache()`, para todos os valores de `key`, a seguinte asserção será sempre verdadeira:

      a = ZoneInfo(key)
      b = ZoneInfo(key)
      assert a is b

  `key` deve estar no formato de um caminho POSIX relativo e normalizado, sem referências de nível superior. O construtor levantará `ValueError` se uma chave não conforme for passada.

  Se nenhum arquivo correspondente a `key` for encontrado, o construtor levantará `ZoneInfoNotFoundError`.

A classe `ZoneInfo` tem dois construtores alternativos:

classmethod `ZoneInfo.``from_file`(fobj, /, key=None)

  Constructs a `ZoneInfo` object from a file-like object returning bytes (e.g. a file opened in binary mode or an `io.BytesIO` object). Unlike the primary constructor, this always constructs a new object.

  The `key` parameter sets the name of the zone for the purposes of `__str__()` and `__repr__()`.

  Objects created via this constructor cannot be pickled (see pickling).

classmethod `ZoneInfo.``no_cache`(key)

  An alternate constructor that bypasses the constructor’s cache. It is identical to the primary constructor, but returns a new object on each call. This is most likely to be useful for testing or demonstration purposes, but it can also be used to create a system with a different cache invalidation strategy.

  Objects created via this constructor will also bypass the cache of a deserializing process when unpickled.

  Cuidado

  Using this constructor may change the semantics of your datetimes in surprising ways, only use it if you know that you need to.

The following class methods are also available:

classmethod `ZoneInfo.``clear_cache`(*, only_keys=None)

  A method for invalidating the cache on the `ZoneInfo` class. If no arguments are passed, all caches are invalidated and the next call to the primary constructor for each key will return a new instance.

  If an iterable of key names is passed to the `only_keys` parameter, only the specified keys will be removed from the cache. Keys passed to `only_keys` but not found in the cache are ignored.

  Aviso

  Invoking this function may change the semantics of datetimes using `ZoneInfo` in surprising ways; this modifies process-wide global state and thus may have wide-ranging effects. Only use it if you know that you need to.

A classe possui um atributo:

`ZoneInfo.``key`

  This is a read-only attribute that returns the value of `key` passed to the constructor, which should be a lookup key in the IANA time zone database (e.g. `America/New_York`, `Europe/Paris` or `Asia/Tokyo`).

  For zones constructed from file without specifying a `key` parameter, this will be set to `None`.

  Nota

  Although it is a somewhat common practice to expose these to end users, these values are designed to be primary keys for representing the relevant zones and not necessarily user-facing elements. Projects like CLDR (the Unicode Common Locale Data Repository) can be used to get more user-friendly strings from these keys.

### String representations

The string representation returned when calling `str` on a `ZoneInfo` object defaults to using the `ZoneInfo.key` attribute (see the note on usage in the attribute documentation):

    >>> zone = ZoneInfo("Pacific/Kwajalein")
    >>> str(zone)
    'Pacific/Kwajalein'

    >>> dt = datetime(2020, 4, 1, 3, 15, tzinfo=zone)
    >>> f"{dt.isoformat()} [{dt.tzinfo}]"
    '2020-04-01T03:15:00+12:00 [Pacific/Kwajalein]'

For objects constructed from a file without specifying a `key` parameter, `str` falls back to calling `repr()`. `ZoneInfo`’s `repr` is implementation-defined and not necessarily stable between versions, but it is guaranteed not to be a valid `ZoneInfo` key.

### Pickle serialization

Rather than serializing all transition data, `ZoneInfo` objects are serialized by key, and `ZoneInfo` objects constructed from files (even those with a value for `key` specified) cannot be pickled.

The behavior of a `ZoneInfo` file depends on how it was constructed:

1. `ZoneInfo(key)`: When constructed with the primary constructor, a `ZoneInfo` object is serialized by key, and when deserialized, the deserializing process uses the primary and thus it is expected that these are expected to be the same object as other references to the same time zone. For example, if `europe_berlin_pkl` is a string containing a pickle constructed from `ZoneInfo("Europe/Berlin")`, one would expect the following behavior:

       >>> a = ZoneInfo("Europe/Berlin")
       >>> b = pickle.loads(europe_berlin_pkl)
       >>> a is b
       True

2. `ZoneInfo.no_cache(key)`: When constructed from the cache-bypassing constructor, the `ZoneInfo` object is also serialized by key, but when deserialized, the deserializing process uses the cache bypassing constructor. If `europe_berlin_pkl_nc` is a string containing a pickle constructed from `ZoneInfo.no_cache("Europe/Berlin")`, one would expect the following behavior:

       >>> a = ZoneInfo("Europe/Berlin")
       >>> b = pickle.loads(europe_berlin_pkl_nc)
       >>> a is b
       False

3. `ZoneInfo.from_file(fobj, /, key=None)`: When constructed from a file, the `ZoneInfo` object raises an exception on pickling. If an end user wants to pickle a `ZoneInfo` constructed from a file, it is recommended that they use a wrapper type or a custom serialization function: either serializing by key or storing the contents of the file object and serializing that.

This method of serialization requires that the time zone data for the required key be available on both the serializing and deserializing side, similar to the way that references to classes and functions are expected to exist in both the serializing and deserializing environments. It also means that no guarantees are made about the consistency of results when unpickling a `ZoneInfo` pickled in an environment with a different version of the time zone data.

## Funções

`zoneinfo.``available_timezones`()

  Get a set containing all the valid keys for IANA time zones available anywhere on the time zone path. This is recalculated on every call to the function.

  This function only includes canonical zone names and does not include “special” zones such as those under the `posix/` and `right/` directories, or the `posixrules` zone.

  Cuidado

  This function may open a large number of files, as the best way to determine if a file on the time zone path is a valid time zone is to read the “magic string” at the beginning.

  Nota

  These values are not designed to be exposed to end-users; for user facing elements, applications should use something like CLDR (the Unicode Common Locale Data Repository) to get more user-friendly strings. See also the cautionary note on `ZoneInfo.key`.

`zoneinfo.``reset_tzpath`(to=None)

  Sets or resets the time zone search path (`TZPATH`) for the module. When called with no arguments, `TZPATH` is set to the default value.

  Calling `reset_tzpath` will not invalidate the `ZoneInfo` cache, and so calls to the primary `ZoneInfo` constructor will only use the new `TZPATH` in the case of a cache miss.

  The `to` parameter must be a sequence of strings or `os.PathLike` and not a string, all of which must be absolute paths. `ValueError` will be raised if something other than an absolute path is passed.

## Globals

`zoneinfo.``TZPATH`

  A read-only sequence representing the time zone search path – when constructing a `ZoneInfo` from a key, the key is joined to each entry in the `TZPATH`, and the first file found is used.

  `TZPATH` may contain only absolute paths, never relative paths, regardless of how it is configured.

  The object that `zoneinfo.TZPATH` points to may change in response to a call to `reset_tzpath()`, so it is recommended to use `zoneinfo.TZPATH` rather than importing `TZPATH` from `zoneinfo` or assigning a long-lived variable to `zoneinfo.TZPATH`.

  For more information on configuring the time zone search path, see Configurando as fontes de dados.

## Exceptions and warnings

exception `zoneinfo.``ZoneInfoNotFoundError`

  Raised when construction of a `ZoneInfo` object fails because the specified key could not be found on the system. This is a subclass of `KeyError`.

exception `zoneinfo.``InvalidTZPathWarning`

  Raised when `PYTHONTZPATH` contains an invalid component that will be filtered out, such as a relative path.