zoneinfo — Prise en charge des fuseaux horaires IANA

Nouveau dans la version 3.9.


Le module zoneinfo fournit une implémentation concrète des fuseaux horaires qui s'appuie sur la base de données de fuseaux horaires IANA spécifiée initialement dans la PEP 615. Par défaut, zoneinfo utilise les données des fuseaux horaires du système si elles sont disponibles, sinon la bibliothèque utilise le paquet quasi-natif tzdata disponible sur PyPI.

Voir aussi

Module : datetime

Fournit les types time et datetime attendus par ZoneInfo.

Paquet tzdata

Paquet « quasi-natif » maintenu par les développeurs de CPython pour fournir les données des fuseaux horaires via PyPI.

Utilisation de ZoneInfo

ZoneInfo est une implémentation concrète de la classe de base abstraite datetime.tzinfo, et est destinée à être rattachée à tzinfo, par le constructeur, par datetime.replace ou par 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'

Les datetime construits de cette manière sont compatibles avec l'arithmétique datetime et gèrent le passage à l'heure d'été sans autre intervention :

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

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

>>> dt_add.tzname()
'PST'

Ces fuseaux horaires prennent aussi en charge l'attribut fold introduit dans la PEP 495. Pendant les transitions des décalages horaires qui induisent des temps ambigus (comme le passage de l'heure d'été à l'heure normale), le décalage avant la transition est utilisé quand fold=0, et le décalage après la transition est utilisé quand fold=1, par exemple :

>>> 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

Lors de la conversion à partir d'un autre fuseau horaire, fold sera réglé à la valeur correcte :

>>> 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

Sources de données

Le module zoninfo ne fournit pas de données de fuseaux horaires directement, mais extrait des informations sur les fuseaux horaires de la base de données des fuseaux horaires du système ou du paquet PyPI quasi-natif tzdata, s'ils sont disponibles. Certains systèmes, comme les systèmes Windows, n'ont pas de base de données IANA, et donc il est recommandé aux projets visant la compatibilité entre plates-formes et qui nécessitent des données sur les fuseaux horaires, de déclarer une dépendance à tzdata. Si aucune donnée système, ni tzdata, n'est disponible, tous les appels à ZoneInfo lèvent ZoneInfoNotFoundError.

Configurer les sources de données

Lorsque ZoneInfo(key) est appelé, le constructeur recherche d'abord un fichier nommé key dans les répertoires spécifiés par TZPATH et, en cas d'échec, recherche dans le paquet tzdata. Ce comportement peut être configuré de trois manières :

  1. La valeur par défaut TZPATH, lorsqu'elle n'est pas spécifiée autrement, peut être configurée à la compilation.

  2. TZPATH peut être configuré en utilisant une variable d'environnement.

  3. À l'exécution, le chemin de recherche peut être manipulé à l'aide de la fonction reset_tzpath().

Configuration à la compilation

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.

Sur toutes les plates-formes, la valeur configurée est disponible en tant que clé de TZPATH dans sysconfig.get_config_var().

Configuration par l'environnement

Lors de l'initialisation de TZPATH (soit au moment de l'importation, soit lorsque reset_tzpath() est appelé sans argument), le module zoneinfo utilise la variable d'environnement PYTHONTZPATH, si elle existe, pour définir le chemin de recherche.

PYTHONTZPATH

This is an os.pathsep-separated string containing the time zone search path to use. It must consist of only absolute rather than relative paths. Relative components specified in PYTHONTZPATH will not be used, but otherwise the behavior when a relative path is specified is implementation-defined; CPython will raise InvalidTZPathWarning, but other implementations are free to silently ignore the erroneous component or raise an exception.

Pour que le système ignore les données système et utilise le paquet tzdata à la place, définissez PYTHONTZPATH="".

Configuration à l'exécution

The TZ search path can also be configured at runtime using the reset_tzpath() function. This is generally not an advisable operation, though it is reasonable to use it in test functions that require the use of a specific time zone path (or require disabling access to the system time zones).

La classe ZoneInfo

class zoneinfo.ZoneInfo(key)

A concrete datetime.tzinfo subclass that represents an IANA time zone specified by the string key. Calls to the primary constructor will always return objects that compare identically; put another way, barring cache invalidation via ZoneInfo.clear_cache(), for all values of key, the following assertion will always be true:

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

key must be in the form of a relative, normalized POSIX path, with no up-level references. The constructor will raise ValueError if a non-conforming key is passed.

If no file matching key is found, the constructor will raise ZoneInfoNotFoundError.

The ZoneInfo class has two alternate constructors:

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.

Prudence

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

Les méthodes de classe suivantes sont également disponibles :

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.

Avertissement

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.

La classe a un attribut :

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.

Note

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.

Fonctions

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.

Prudence

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.

Note

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 Configurer les sources de données.

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.