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python-pyicu - Python extension wrapping the ICU C++ API…  more info»


README file for PyICU

.. contents::


Welcome to PyICU, a Python extension wrapping IBM's International
Components for Unicode C++ library (ICU).

PyICU is a project maintained by the Open Source Applications Foundation.

The ICU homepage is:

Building PyICU

Before building PyICU the ICU libraries must be built and installed. Refer
to each system's instructions for more information.

PyICU is built with distutils or setuptools:
   - verify that the ``INCLUDES``, ``LFLAGS``, ``CFLAGS`` and ``LIBRARIES``
     dictionaries in ```` contain correct values for your platform
   - ``python build``
   - ``sudo python install``

Running PyICU

  - Mac OS X
    Make sure that ``DYLD_LIBRARY_PATH`` contains paths to the directory(ies)
    containing the ICU libs.

  - Linux & Solaris
    Make sure that ``LD_LIBRARY_PATH`` contains paths to the directory(ies)
    containing the ICU libs or that you added the corresponding ``-rpath``
    argument to ``LFLAGS``.

  - Windows
    Make sure that ``PATH`` contains paths to the directory(ies)
    containing the ICU DLLs.

What's available

See the ``CHANGES`` file for an up to date log of changes and additions.

API Documentation

There is no API documentation for PyICU. The API for ICU is documented at and the following patterns can be
used to translate from the C++ APIs to the corresponding Python APIs.

  - strings

    The ICU string type, ``UnicodeString``, is a type pointing at a mutable
    array of ``UChar`` Unicode 16-bit wide characters. The Python unicode type
    is an immutable string of 16-bit or 32-bit wide Unicode characters.

    Because of these differences, ``UnicodeString`` and Python's ``unicode``
    type are not merged into the same type when crossing the C++ boundary.
    ICU APIs taking ``UnicodeString`` arguments have been overloaded to also
    accept Python str or unicode type arguments. In the case of ``str``
    objects, ``utf-8`` encoding is assumed when converting them to
    ``UnicodeString`` objects.

    To convert a Python ``str`` encoded in a encoding other than ``utf-8`` to
    an ICU ``UnicodeString`` use the ``UnicodeString(str, encodingName)``

    ICU's C++ APIs accept and return ``UnicodeString`` arguments in several
    ways: by value, by pointer or by reference.
    When an ICU C++ API is documented to accept a ``UnicodeString`` reference
    parameter, it is safe to assume that there are several corresponding
    PyICU python APIs making it accessible in simpler ways:

    For example, the
    ``'UnicodeString &Locale::getDisplayName(UnicodeString &)'`` API,
    documented at
    can be invoked from Python in several ways:

    1. The ICU way

        >>> from icu import UnicodeString, Locale
        >>> locale = Locale('pt_BR')
        >>> string = UnicodeString()
        >>> name = locale.getDisplayName(string)
        >>> name
        <UnicodeString: Portuguese (Brazil)>
        >>> name is string
        True                  <-- string arg was returned, modified in place

    2. The Python way

        >>> from icu import Locale
        >>> locale = Locale('pt_BR')
        >>> name = locale.getDisplayName()
        >>> name
        u'Portuguese (Brazil)'

        A ``UnicodeString`` object was allocated and converted to a Python
        ``unicode`` object.

    A UnicodeString can be coerced to a Python unicode string with Python's
    ``unicode()`` constructor. The usual ``len()``, ``str()``, comparison,
    ``[]`` and ``[:]`` operators are all available, with the additional
    twists that slicing is not read-only and that ``+=`` is also available
    since a UnicodeString is mutable. For example:

        >>> name = locale.getDisplayName()
        u'Portuguese (Brazil)'
        >>> name = UnicodeString(name)
        >>> name
        <UnicodeString: Portuguese (Brazil)>
        >>> unicode(name)
        u'Portuguese (Brazil)'
        >>> len(name)
        >>> str(name)           <-- works when chars fit with default encoding
        'Portuguese (Brazil)'
        >>> name[3]
        >>> name[12:18]
        <UnicodeString: Brazil>
        >>> name[12:18] = 'the country of Brasil'
        >>> name
        <UnicodeString: Portuguese (the country of Brasil)>
        >>> name += ' oh joy'
        >>> name
        <UnicodeString: Portuguese (the country of Brasil) oh joy>

  - error reporting

    The C++ ICU library does not use C++ exceptions to report errors. ICU
    C++ APIs return errors via a ``UErrorCode`` reference argument. All such
    APIs are wrapped by Python APIs that omit this argument and throw an
    ``ICUError`` Python exception instead. The same is true for ICU APIs
    taking both a ``ParseError`` and a ``UErrorCode``, they are both to be

    For example, the ``'UnicodeString &DateFormat::format(const Formattable &,
    UnicodeString &, UErrorCode &)'`` API, documented at
    is invoked from Python with:

        >>> from icu import DateFormat, Formattable
        >>> df = DateFormat.createInstance()
        >>> df
        <SimpleDateFormat: M/d/yy h:mm a>
        >>> f = Formattable(940284258.0, Formattable.kIsDate)
        >>> df.format(f)
        u'10/18/99 3:04 PM'
    Of course, the simpler ``'UnicodeString &DateFormat::format(UDate,
    UnicodeString &)'`` documented here:
    can be used too:

        >>> from icu import DateFormat
        >>> df = DateFormat.createInstance()
        >>> df
        <SimpleDateFormat: M/d/yy h:mm a>
        >>> df.format(940284258.0)
        u'10/18/99 3:04 PM'

  - dates

    ICU uses a double floating point type called ``UDate`` that represents the
    number of milliseconds elapsed since 1970-jan-01 UTC for dates.

    In Python, the value returned by the ``time`` module's ``time()``
    function is the number of seconds since 1970-jan-01 UTC. Because of this
    difference, floating point values are multiplied by 1000 when passed to
    APIs taking ``UDate`` and divided by 1000 when returned as ``UDate``.

    Python's ``datetime`` objects, with or without timezone information, can
    also be used with APIs taking ``UDate`` arguments. The ``datetime``
    objects get converted to ``UDate`` when crossing into the C++ layer.

  - arrays

    Many ICU API take array arguments. A list of elements of the array
    element types is to be passed from Python.

  - StringEnumeration

    An ICU ``StringEnumeration`` has three ``next`` methods: ``next()`` which
    returns a ``str`` objects, ``unext()`` which returns ``unicode`` objects
    and ``snext()`` which returns ``UnicodeString`` objects.
    Any of these methods can be used as an iterator, using the Python
    built-in ``iter`` function. 

    For example, let ``e`` be a ``StringEnumeration`` instance::

      [s for s in e] is a list of 'str' objects
      [s for s in iter(e.unext, None)] is a list of 'unicode' objects
      [s for s in iter(e.snext, None)] is a list of 'UnicodeString' objects

  - timezones

    The ICU ``TimeZone`` type may be wrapped with an ``ICUtzinfo`` type for
    usage with Python's ``datetime`` type. For example::

       tz = ICUtzinfo(TimeZone.createTimeZone('US/Mountain'))

    or, even simpler::

       tz = ICUtzinfo.getInstance('Pacific/Fiji')

    To get the default time zone use::

       defaultTZ = ICUtzinfo.getDefault()

    To get the time zone's id, use the ``tzid`` attribute or coerce the time
    zone to a string::

       ICUtzinfo.getInstance('Pacific/Fiji').tzid -> 'Pacific/Fiji'
       str(ICUtzinfo.getInstance('Pacific/Fiji')) -> 'Pacific/Fiji'
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