~ubuntu-branches/ubuntu/trusty/python-tz/trusty

Metadata-Version: 1.0
Name: pytz
Version: 2009p
Summary: World timezone definitions, modern and historical
Home-page: http://pytz.sourceforge.net
Author: Stuart Bishop
Author-email: stuart@stuartbishop.net
License: MIT
Download-URL: http://pypi.python.org/pypi/pytz
Description: pytz - World Timezone Definitions for Python
        ============================================
        
        :Author: Stuart Bishop <stuart@stuartbishop.net>
        
        Introduction
        ~~~~~~~~~~~~
        
        pytz brings the Olson tz database into Python. This library allows
        accurate and cross platform timezone calculations using Python 2.3
        or higher. It also solves the issue of ambiguous times at the end
        of daylight savings, which you can read more about in the Python
        Library Reference (datetime.tzinfo).
        
        Amost all of the Olson timezones are supported.
        
        Note that this library differs from the documented Python API for
        tzinfo implementations; if you want to create local wallclock
        times you need to use the localize() method documented in this
        document. In addition, if you perform date arithmetic on local
        times that cross DST boundaries, the results may be in an incorrect
        timezone (ie. subtract 1 minute from 2002-10-27 1:00 EST and you get
        2002-10-27 0:59 EST instead of the correct 2002-10-27 1:59 EDT). A
        normalize() method is provided to correct this. Unfortunatly these
        issues cannot be resolved without modifying the Python datetime
        implementation.
        
        
        Installation
        ~~~~~~~~~~~~
        
        This package can either be installed from a .egg file using setuptools,
        or from the tarball using the standard Python distutils.
        
        If you are installing from a tarball, run the following command as an
        administrative user::
        
        python setup.py install
        
        If you are installing using setuptools, you don't even need to download
        anything as the latest version will be downloaded for you
        from the Python package index::
        
        easy_install --upgrade pytz
        
        If you already have the .egg file, you can use that too::
        
        easy_install pytz-2008g-py2.6.egg
        
        
        Example & Usage
        ~~~~~~~~~~~~~~~
        
        >>> from datetime import datetime, timedelta
        >>> from pytz import timezone
        >>> import pytz
        >>> utc = pytz.utc
        >>> utc.zone
        'UTC'
        >>> eastern = timezone('US/Eastern')
        >>> eastern.zone
        'US/Eastern'
        >>> amsterdam = timezone('Europe/Amsterdam')
        >>> fmt = '%Y-%m-%d %H:%M:%S %Z%z'
        
        This library only supports two ways of building a localized time. The
        first is to use the .localize() method provided by the pytz library.
        This is used to localize a naive datetime (datetime with no timezone
        information):
        
        >>> loc_dt = eastern.localize(datetime(2002, 10, 27, 6, 0, 0))
        >>> print loc_dt.strftime(fmt)
        2002-10-27 06:00:00 EST-0500
        
        The second way of building a localized time is by converting an existing
        localized time using the standard .astimezone() method:
        
        >>> ams_dt = loc_dt.astimezone(amsterdam)
        >>> ams_dt.strftime(fmt)
        '2002-10-27 12:00:00 CET+0100'
        
        Unfortunately using the tzinfo argument of the standard datetime
        constructors ''does not work'' with pytz for many timezones.
        
        >>> datetime(2002, 10, 27, 12, 0, 0, tzinfo=amsterdam).strftime(fmt)
        '2002-10-27 12:00:00 AMT+0020'
        
        It is safe for timezones without daylight savings trasitions though, such
        as UTC:
        
        >>> datetime(2002, 10, 27, 12, 0, 0, tzinfo=pytz.utc).strftime(fmt)
        '2002-10-27 12:00:00 UTC+0000'
        
        The preferred way of dealing with times is to always work in UTC,
        converting to localtime only when generating output to be read
        by humans.
        
        >>> utc_dt = datetime(2002, 10, 27, 6, 0, 0, tzinfo=utc)
        >>> loc_dt = utc_dt.astimezone(eastern)
        >>> loc_dt.strftime(fmt)
        '2002-10-27 01:00:00 EST-0500'
        
        This library also allows you to do date arithmetic using local
        times, although it is more complicated than working in UTC as you
        need to use the `normalize` method to handle daylight savings time
        and other timezone transitions. In this example, `loc_dt` is set
        to the instant when daylight savings time ends in the US/Eastern
        timezone.
        
        >>> before = loc_dt - timedelta(minutes=10)
        >>> before.strftime(fmt)
        '2002-10-27 00:50:00 EST-0500'
        >>> eastern.normalize(before).strftime(fmt)
        '2002-10-27 01:50:00 EDT-0400'
        >>> after = eastern.normalize(before + timedelta(minutes=20))
        >>> after.strftime(fmt)
        '2002-10-27 01:10:00 EST-0500'
        
        Creating localtimes is also tricky, and the reason why working with
        local times is not recommended. Unfortunately, you cannot just pass
        a 'tzinfo' argument when constructing a datetime (see the next section
        for more details)
        
        >>> dt = datetime(2002, 10, 27, 1, 30, 0)
        >>> dt1 = eastern.localize(dt, is_dst=True)
        >>> dt1.strftime(fmt)
        '2002-10-27 01:30:00 EDT-0400'
        >>> dt2 = eastern.localize(dt, is_dst=False)
        >>> dt2.strftime(fmt)
        '2002-10-27 01:30:00 EST-0500'
        
        Converting between timezones also needs special attention. This also needs
        to use the normalize method to ensure the conversion is correct.
        
        >>> utc_dt = utc.localize(datetime.utcfromtimestamp(1143408899))
        >>> utc_dt.strftime(fmt)
        '2006-03-26 21:34:59 UTC+0000'
        >>> au_tz = timezone('Australia/Sydney')
        >>> au_dt = au_tz.normalize(utc_dt.astimezone(au_tz))
        >>> au_dt.strftime(fmt)
        '2006-03-27 08:34:59 EST+1100'
        >>> utc_dt2 = utc.normalize(au_dt.astimezone(utc))
        >>> utc_dt2.strftime(fmt)
        '2006-03-26 21:34:59 UTC+0000'
        
        You can take shortcuts when dealing with the UTC side of timezone
        conversions. Normalize and localize are not really necessary when there
        are no daylight savings time transitions to deal with.
        
        >>> utc_dt = datetime.utcfromtimestamp(1143408899).replace(tzinfo=utc)
        >>> utc_dt.strftime(fmt)
        '2006-03-26 21:34:59 UTC+0000'
        >>> au_tz = timezone('Australia/Sydney')
        >>> au_dt = au_tz.normalize(utc_dt.astimezone(au_tz))
        >>> au_dt.strftime(fmt)
        '2006-03-27 08:34:59 EST+1100'
        >>> utc_dt2 = au_dt.astimezone(utc)
        >>> utc_dt2.strftime(fmt)
        '2006-03-26 21:34:59 UTC+0000'
        
        
        Problems with Localtime
        ~~~~~~~~~~~~~~~~~~~~~~~
        
        The major problem we have to deal with is that certain datetimes
        may occur twice in a year. For example, in the US/Eastern timezone
        on the last Sunday morning in October, the following sequence
        happens:
        
        - 01:00 EDT occurs
        - 1 hour later, instead of 2:00am the clock is turned back 1 hour
        and 01:00 happens again (this time 01:00 EST)
        
        In fact, every instant between 01:00 and 02:00 occurs twice. This means
        that if you try and create a time in the US/Eastern timezone using
        the standard datetime syntax, there is no way to specify if you meant
        before of after the end-of-daylight-savings-time transition.
        
        >>> loc_dt = datetime(2002, 10, 27, 1, 30, 00, tzinfo=eastern)
        >>> loc_dt.strftime(fmt)
        '2002-10-27 01:30:00 EST-0500'
        
        As you can see, the system has chosen one for you and there is a 50%
        chance of it being out by one hour. For some applications, this does
        not matter. However, if you are trying to schedule meetings with people
        in different timezones or analyze log files it is not acceptable.
        
        The best and simplest solution is to stick with using UTC.  The pytz
        package encourages using UTC for internal timezone representation by
        including a special UTC implementation based on the standard Python
        reference implementation in the Python documentation.  This timezone
        unpickles to be the same instance, and pickles to a relatively small
        size.  The UTC implementation can be obtained as pytz.utc, pytz.UTC,
        or pytz.timezone('UTC').
        
        >>> import pickle, pytz
        >>> dt = datetime(2005, 3, 1, 14, 13, 21, tzinfo=utc)
        >>> naive = dt.replace(tzinfo=None)
        >>> p = pickle.dumps(dt, 1)
        >>> naive_p = pickle.dumps(naive, 1)
        >>> len(p), len(naive_p), len(p) - len(naive_p)
        (60, 43, 17)
        >>> new = pickle.loads(p)
        >>> new == dt
        True
        >>> new is dt
        False
        >>> new.tzinfo is dt.tzinfo
        True
        >>> pytz.utc is pytz.UTC is pytz.timezone('UTC')
        True
        
        Note that this instance is not the same instance (or implementation) as
        other timezones with the same meaning (GMT, Greenwich, Universal, etc.).
        
        >>> utc is pytz.timezone('GMT')
        False
        
        If you insist on working with local times, this library provides a
        facility for constructing them unambiguously:
        
        >>> loc_dt = datetime(2002, 10, 27, 1, 30, 00)
        >>> est_dt = eastern.localize(loc_dt, is_dst=True)
        >>> edt_dt = eastern.localize(loc_dt, is_dst=False)
        >>> print est_dt.strftime(fmt), '/', edt_dt.strftime(fmt)
        2002-10-27 01:30:00 EDT-0400 / 2002-10-27 01:30:00 EST-0500
        
        If you pass None as the is_dst flag to localize(), pytz will refuse to
        guess and raise exceptions if you try to build ambiguous or non-existent
        times.
        
        For example, 1:30am on 27th Oct 2002 happened twice in the US/Eastern
        timezone when the clocks where put back at the end of Daylight Savings
        Time:
        
        >>> eastern.localize(datetime(2002, 10, 27, 1, 30, 00), is_dst=None)
        Traceback (most recent call last):
        ...
        AmbiguousTimeError: 2002-10-27 01:30:00
        
        Similarly, 2:30am on 7th April 2002 never happened at all in the
        US/Eastern timezone, as the clock where put forward at 2:00am skipping
        the entire hour:
        
        >>> eastern.localize(datetime(2002, 4, 7, 2, 30, 00), is_dst=None)
        Traceback (most recent call last):
        ...
        NonExistentTimeError: 2002-04-07 02:30:00
        
        Both of these exceptions share a common base class to make error handling
        easier:
        
        >>> isinstance(pytz.AmbiguousTimeError(), pytz.InvalidTimeError)
        True
        >>> isinstance(pytz.NonExistentTimeError(), pytz.InvalidTimeError)
        True
        
        Although localize() handles many cases, it is still not possible
        to handle all. In cases where countries change their timezone definitions,
        cases like the end-of-daylight-savings-time occur with no way of resolving
        the ambiguity. For example, in 1915 Warsaw switched from Warsaw time to
        Central European time. So at the stroke of midnight on August 5th 1915
        the clocks were wound back 24 minutes creating an ambiguous time period
        that cannot be specified without referring to the timezone abbreviation
        or the actual UTC offset. In this case midnight happened twice, neither
        time during a daylight savings time period:
        
        >>> warsaw = pytz.timezone('Europe/Warsaw')
        >>> loc_dt1 = warsaw.localize(datetime(1915, 8, 4, 23, 59, 59), is_dst=False)
        >>> loc_dt1.strftime(fmt)
        '1915-08-04 23:59:59 WMT+0124'
        >>> loc_dt2 = warsaw.localize(datetime(1915, 8, 5, 00, 00, 00), is_dst=False)
        >>> loc_dt2.strftime(fmt)
        '1915-08-05 00:00:00 CET+0100'
        >>> str(loc_dt2 - loc_dt1)
        '0:24:01'
        
        The only way of creating a time during the missing 24 minutes is converting
        from another time - because neither of the timezones involved where in
        daylight savings mode the API simply provides no way to express it:
        
        >>> utc_dt = datetime(1915, 8, 4, 22, 36, tzinfo=pytz.utc)
        >>> utc_dt.astimezone(warsaw).strftime(fmt)
        '1915-08-04 23:36:00 CET+0100'
        
        The 'Standard' Python way of handling all these ambiguities is not to,
        such as demonstrated in this example using the US/Eastern timezone
        definition from the Python documentation (Note that this implementation
        only works for dates between 1987 and 2006 - it is included for tests only!):
        
        >>> from pytz.reference import Eastern # pytz.reference only for tests
        >>> dt = datetime(2002, 10, 27, 0, 30, tzinfo=Eastern)
        >>> str(dt)
        '2002-10-27 00:30:00-04:00'
        >>> str(dt + timedelta(hours=1))
        '2002-10-27 01:30:00-05:00'
        >>> str(dt + timedelta(hours=2))
        '2002-10-27 02:30:00-05:00'
        >>> str(dt + timedelta(hours=3))
        '2002-10-27 03:30:00-05:00'
        
        Notice the first two results? At first glance you might think they are
        correct, but taking the UTC offset into account you find that they are
        actually two hours appart instead of the 1 hour we asked for.
        
        >>> from pytz.reference import UTC # pytz.reference only for tests
        >>> str(dt.astimezone(UTC))
        '2002-10-27 04:30:00+00:00'
        >>> str((dt + timedelta(hours=1)).astimezone(UTC))
        '2002-10-27 06:30:00+00:00'
        
        
        Country Information
        ~~~~~~~~~~~~~~~~~~~
        
        A mechanism is provided to access the timezones commonly in use
        for a particular country, looked up using the ISO 3166 country code.
        It returns a list of strings that can be used to retrieve the relevant
        tzinfo instance using `pytz.timezone()`:
        
        >>> pytz.country_timezones['nz']
        ['Pacific/Auckland', 'Pacific/Chatham']
        
        The Olson database comes with a ISO 3166 country code to English country
        name mapping that pytz exposes as a dictionary:
        
        >>> pytz.country_names['nz']
        'New Zealand'
        
        
        What is UTC
        ~~~~~~~~~~~
        
        `UTC` is Universal Time, also known as Greenwich Mean Time or GMT
        in the United Kingdom. All other timezones are given as offsets from
        UTC. No daylight savings time occurs in UTC, making it a useful timezone
        to perform date arithmetic without worrying about the confusion and
        ambiguities caused by daylight savings time transitions, your country
        changing its timezone, or mobile computers that move roam through
        multiple timezones.
        
        
        Helpers
        ~~~~~~~
        
        There are two lists of timezones provided.
        
        `all_timezones` is the exhaustive list of the timezone names that can be used.
        
        >>> from pytz import all_timezones
        >>> len(all_timezones) >= 500
        True
        >>> 'Etc/Greenwich' in all_timezones
        True
        
        `common_timezones` is a list of useful, current timezones. It doesn't
        contain deprecated zones or historical zones, except for a few I've
        deemed in common usage, such as US/Eastern (open a bug report if you
        think other timezones are deserving of being included here).It is also
        a sequence of strings.
        
        >>> from pytz import common_timezones
        >>> len(common_timezones) < len(all_timezones)
        True
        >>> 'Etc/Greenwich' in common_timezones
        False
        >>> 'US/Eastern' in common_timezones
        True
        >>> 'Australia/Melbourne' in common_timezones
        True
        >>> 'US/Pacific-New' in all_timezones
        True
        >>> 'US/Pacific-New' in common_timezones
        False
        
        Both common_timezones and all_timezones are alphabetically sorted:
        
        >>> common_timezones_dupe = common_timezones[:]
        >>> common_timezones_dupe.sort()
        >>> common_timezones == common_timezones_dupe
        True
        >>> all_timezones_dupe = all_timezones[:]
        >>> all_timezones_dupe.sort()
        >>> all_timezones == all_timezones_dupe
        True
        
        `all_timezones` and `common_timezones` are also available as sets.
        
        >>> from pytz import all_timezones_set, common_timezones_set
        >>> 'US/Eastern' in all_timezones_set
        True
        >>> 'US/Eastern' in common_timezones_set
        True
        >>> 'Australia/Victoria' in common_timezones_set
        False
        
        You can also retrieve lists of timezones used by particular countries
        using the `country_timezones()` method. It requires an ISO-3166 two letter
        country code.
        
        >>> from pytz import country_timezones
        >>> country_timezones('ch')
        ['Europe/Zurich']
        >>> country_timezones('CH')
        ['Europe/Zurich']
        
        License
        ~~~~~~~
        
        MIT license.
        
        This code is also available as part of Zope 3 under the Zope Public
        License,  Version 2.1 (ZPL).
        
        I'm happy to relicense this code if necessary for inclusion in other
        open source projects.
        
        Latest Versions
        ~~~~~~~~~~~~~~~
        
        This package will be updated after releases of the Olson timezone
        database.  The latest version can be downloaded from the Python Package
        Index (PyPI_).  The code that is used to generate this distribution is
        hosted on launchpad.net and available using the Bazaar_ revision control
        system using::
        
        bzr branch lp:pytz
        
        .. _PyPI: http://cheeseshop.python.org/pypi/pytz/
        .. _Bazaar: http://bazaar-vcs.org/
        
        Bugs, Feature Requests & Patches
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        
        Bugs can be reported using Launchpad at
        https://bugs.launchpad.net/products/pytz
        
        Issues & Limitations
        ~~~~~~~~~~~~~~~~~~~~
        
        - Offsets from UTC are rounded to the nearest whole minute, so timezones
        such as Europe/Amsterdam pre 1937 will be up to 30 seconds out. This is
        a limitation of the Python datetime library.
        
        - If you think a timezone definition is incorrect, I probably can't fix
        it. pytz is a direct translation of the Olson timezone database, and
        changes to the timezone definitions need to be made to this source.
        If you find errors they should be reported to the time zone mailing
        list, linked from http://www.twinsun.com/tz/tz-link.htm
        
        Further Reading
        ~~~~~~~~~~~~~~~
        
        More info than you want to know about timezones:
        http://www.twinsun.com/tz/tz-link.htm
        
        
        Contact
        ~~~~~~~
        
        Stuart Bishop <stuart@stuartbishop.net>
        
        
Keywords: timezone,tzinfo,datetime,olson,time
Platform: Independant
Classifier: Development Status :: 6 - Mature
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: MIT License
Classifier: Natural Language :: English
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python
Classifier: Topic :: Software Development :: Libraries :: Python Modules