Python extension wrapping the ICU C++ API
Project description
README file for PyICU
Welcome
Welcome to PyICU, a Python extension wrapping the ICU C++ libraries.
ICU stands for "International Components for Unicode". These are the i18n libraries of the Unicode Consortium. They implement much of the Unicode Standard, many of its companion Unicode Technical Standards, and much of Unicode CLDR.
The PyICU source code is hosted on GitHub at https://github.com/ovalhub/pyicu.
The ICU homepage is http://site.icu-project.org/
See also the CLDR homepage at http://cldr.unicode.org/
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 icu-config program is available or that the
INCLUDES
,LFLAGS
,CFLAGS
andLIBRARIES
dictionaries insetup.py
contain correct values for your platform. Starting with ICU 60, -std=c++11 must appear in your CFLAGS. python setup.py build
sudo python setup.py 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 toLFLAGS
. -
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 http://icu-project.org/apiref/icu4c/ 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, the utf-8
encoding is assumed when converting them to
UnicodeString
objects.
To convert a Python str
encoded in an encoding other than utf-8
to
an ICU UnicodeString
use the UnicodeString(str, encodingName)
constructor.
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
http://icu-project.org/apiref/icu4c/classLocale.html
can be invoked from Python in several ways:
-
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
-
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 Pythonunicode
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)
19
>>> str(name) <-- works when chars fit with default encoding
'Portuguese (Brazil)'
>>> name[3]
u't'
>>> 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
omitted.
For example, the 'UnicodeString &DateFormat::format(const Formattable &, UnicodeString &, UErrorCode &)'
API, documented at
http://icu-project.org/apiref/icu4c/classDateFormat.html
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:
http://icu-project.org/apiref/icu4c/classDateFormat.html
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'))
datetime.now(tz)
or, even simpler::
tz = ICUtzinfo.getInstance('Pacific/Fiji')
datetime.now(tz)
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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