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"""Wraps the best available JSON implementation available in a common
interface"""
import sys
__version__ = "0.2.3"
__author__ = "Rune Halvorsen <runefh@gmail.com>"
__homepage__ = "http://bitbucket.org/runeh/anyjson/"
__docformat__ = "restructuredtext"
implementation = None
"""
.. function:: serialize(obj)
Serialize the object to JSON.
.. function:: deserialize(str)
Deserialize JSON-encoded object to a Python object.
.. function:: force_implementation(name)
Load a specific json module. This is useful for testing and not much else
.. attribute:: implementation
The json implementation object. This is probably not useful to you,
except to get the name of the implementation in use. The name is
available through `implementation.name`.
.. data:: _modules
List of known json modules, and the names of their serialize/unserialize
methods, as well as the exception they throw. Exception can be either
an exception class or a string.
"""
_modules = [("yajl", "dumps", TypeError, "loads", ValueError),
("cjson", "encode", "EncodeError", "decode", "DecodeError"),
("jsonlib2", "write", "WriteError", "read", "ReadError"),
("jsonlib", "write", "WriteError", "read", "ReadError"),
("simplejson", "dumps", TypeError, "loads", ValueError),
("json", "dumps", TypeError, "loads", ValueError),
("django.utils.simplejson", "dumps", TypeError, "loads",
ValueError)]
_fields = ("modname", "encoder", "encerror", "decoder", "decerror")
class _JsonImplementation(object):
"""Incapsulates a JSON implementation"""
def __init__(self, modspec):
modinfo = dict(zip(_fields, modspec))
# No try block. We want importerror to end up at caller
module = self._attempt_load(modinfo["modname"])
self.implementation = modinfo["modname"]
self._encode = getattr(module, modinfo["encoder"])
self._decode = getattr(module, modinfo["decoder"])
self._encode_error = modinfo["encerror"]
self._decode_error = modinfo["decerror"]
if isinstance(modinfo["encerror"], basestring):
self._encode_error = getattr(module, modinfo["encerror"])
if isinstance(modinfo["decerror"], basestring):
self._decode_error = getattr(module, modinfo["decerror"])
self.name = modinfo["modname"]
def __str__(self):
return "<_JsonImplementation instance using %s>" % self.name
def _attempt_load(self, modname):
"""Attempt to load module name modname, returning it on success,
throwing ImportError if module couldn't be imported"""
__import__(modname)
return sys.modules[modname]
def serialize(self, data):
"""Serialize the datastructure to json. Returns a string. Raises
TypeError if the object could not be serialized."""
try:
return self._encode(data)
except self._encode_error, exc:
raise TypeError(*exc.args)
def deserialize(self, s):
"""deserialize the string to python data types. Raises
ValueError if the string vould not be parsed."""
try:
return self._decode(s)
except self._decode_error, exc:
raise ValueError(*exc.args)
def force_implementation(modname):
"""Forces anyjson to use a specific json module if it's available"""
global implementation
for name, spec in [(e[0], e) for e in _modules]:
if name == modname:
implementation = _JsonImplementation(spec)
return
raise ImportError("No module named: %s" % modname)
if __name__ == "__main__":
# If run as a script, we do nothing but print an error message.
# We do NOT try to load a compatible module because that may throw an
# exception, which renders the package uninstallable with easy_install
# (It trys to execfile the script when installing, to make sure it works)
print "Running anyjson as a stand alone script is not supported"
sys.exit(1)
else:
for modspec in _modules:
try:
implementation = _JsonImplementation(modspec)
break
except ImportError:
pass
else:
raise ImportError("No supported JSON module found")
serialize = lambda value: implementation.serialize(value)
deserialize = lambda value: implementation.deserialize(value)
|
