您的位置:首页 > 编程语言 > Python开发

python2.5版本中实现简单的json模块

2014-05-26 20:22 866 查看
项目开发中用到了一个工具,使用python2.5版本的,但是现在需要使用json模块,2.5版本中还没有集成json模块,python2.5又是集成在工具中的,不好升级,况且工具又是前人写的,都不熟悉,由于只用到了dumps这个函数,所有就自己从python2.7版本的源码中扒了这函数下来。

这里最主要的是两个类,json和encoder:

改编后如下:

(1)myJson

r"""JSON (JavaScript Object Notation) <http://json.org> is a subset of
JavaScript syntax (ECMA-262 3rd edition) used as a lightweight data
interchange format.

:mod:`json` exposes an API familiar to users of the standard library
:mod:`marshal` and :mod:`pickle` modules. It is the externally maintained
version of the :mod:`json` library contained in Python 2.6, but maintains
compatibility with Python 2.4 and Python 2.5 and (currently) has
significant performance advantages, even without using the optional C
extension for speedups.

Encoding basic Python object hierarchies::

>>> import json
>>> json.dumps(['foo', {'bar': ('baz', None, 1.0, 2)}])
'["foo", {"bar": ["baz", null, 1.0, 2]}]'
>>> print json.dumps("\"foo\bar")
"\"foo\bar"
>>> print json.dumps(u'\u1234')
"\u1234"
>>> print json.dumps('\\')
"\\"
>>> print json.dumps({"c": 0, "b": 0, "a": 0}, sort_keys=True)
{"a": 0, "b": 0, "c": 0}
>>> from StringIO import StringIO
>>> io = StringIO()
>>> json.dump(['streaming API'], io)
>>> io.getvalue()
'["streaming API"]'

Compact encoding::

>>> import json
>>> json.dumps([1,2,3,{'4': 5, '6': 7}], sort_keys=True, separators=(',',':'))
'[1,2,3,{"4":5,"6":7}]'

Pretty printing::

>>> import json
>>> print json.dumps({'4': 5, '6': 7}, sort_keys=True,
...                  indent=4, separators=(',', ': '))
{
"4": 5,
"6": 7
}

Decoding JSON::

>>> import json
>>> obj = [u'foo', {u'bar': [u'baz', None, 1.0, 2]}]
>>> json.loads('["foo", {"bar":["baz", null, 1.0, 2]}]') == obj
True
>>> json.loads('"\\"foo\\bar"') == u'"foo\x08ar'
True
>>> from StringIO import StringIO
>>> io = StringIO('["streaming API"]')
>>> json.load(io)[0] == 'streaming API'
True

Specializing JSON object decoding::

>>> import json
>>> def as_complex(dct):
...     if '__complex__' in dct:
...         return complex(dct['real'], dct['imag'])
...     return dct
...
>>> json.loads('{"__complex__": true, "real": 1, "imag": 2}',
...     object_hook=as_complex)
(1+2j)
>>> from decimal import Decimal
>>> json.loads('1.1', parse_float=Decimal) == Decimal('1.1')
True

Specializing JSON object encoding::

>>> import json
>>> def encode_complex(obj):
...     if isinstance(obj, complex):
...         return [obj.real, obj.imag]
...     raise TypeError(repr(o) + " is not JSON serializable")
...
>>> json.dumps(2 + 1j, default=encode_complex)
'[2.0, 1.0]'
>>> json.JSONEncoder(default=encode_complex).encode(2 + 1j)
'[2.0, 1.0]'
>>> ''.join(json.JSONEncoder(default=encode_complex).iterencode(2 + 1j))
'[2.0, 1.0]'

Using json.tool from the shell to validate and pretty-print::

$ echo '{"json":"obj"}' | python -m json.tool
{
"json": "obj"
}
$ echo '{ 1.2:3.4}' | python -m json.tool
Expecting property name enclosed in double quotes: line 1 column 3 (char 2)
"""
__version__ = '2.0.9'
__all__ = [
'dump', 'dumps', 'load', 'loads',
'JSONDecoder', 'JSONEncoder',
]

__author__ = 'Bob Ippolito <bob@redivi.com>'

from myencoder import JSONEncoder

_default_encoder = JSONEncoder(
skipkeys=False,
ensure_ascii=True,
check_circular=True,
allow_nan=True,
indent=None,
separators=None,
encoding='utf-8',
default=None,
)

def dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True,
allow_nan=True, cls=None, indent=None, separators=None,
encoding='utf-8', default=None, sort_keys=False, **kw):
"""Serialize ``obj`` to a JSON formatted ``str``.

If ``skipkeys`` is false then ``dict`` keys that are not basic types
(``str``, ``unicode``, ``int``, ``long``, ``float``, ``bool``, ``None``)
will be skipped instead of raising a ``TypeError``.

If ``ensure_ascii`` is false, all non-ASCII characters are not escaped, and
the return value may be a ``unicode`` instance. See ``dump`` for details.

If ``check_circular`` is false, then the circular reference check
for container types will be skipped and a circular reference will
result in an ``OverflowError`` (or worse).

If ``allow_nan`` is false, then it will be a ``ValueError`` to
serialize out of range ``float`` values (``nan``, ``inf``, ``-inf``) in
strict compliance of the JSON specification, instead of using the
JavaScript equivalents (``NaN``, ``Infinity``, ``-Infinity``).

If ``indent`` is a non-negative integer, then JSON array elements and
object members will be pretty-printed with that indent level. An indent
level of 0 will only insert newlines. ``None`` is the most compact
representation.  Since the default item separator is ``', '``,  the
output might include trailing whitespace when ``indent`` is specified.
You can use ``separators=(',', ': ')`` to avoid this.

If ``separators`` is an ``(item_separator, dict_separator)`` tuple
then it will be used instead of the default ``(', ', ': ')`` separators.
``(',', ':')`` is the most compact JSON representation.

``encoding`` is the character encoding for str instances, default is UTF-8.

``default(obj)`` is a function that should return a serializable version
of obj or raise TypeError. The default simply raises TypeError.

If *sort_keys* is ``True`` (default: ``False``), then the output of
dictionaries will be sorted by key.

To use a custom ``JSONEncoder`` subclass (e.g. one that overrides the
``.default()`` method to serialize additional types), specify it with
the ``cls`` kwarg; otherwise ``JSONEncoder`` is used.

"""
# cached encoder
if (not skipkeys and ensure_ascii and
check_circular and allow_nan and
cls is None and indent is None and separators is None and
encoding == 'utf-8' and default is None and not sort_keys and not kw):
return _default_encoder.encode(obj)
if cls is None:
cls = JSONEncoder
return cls(
skipkeys=skipkeys, ensure_ascii=ensure_ascii,
check_circular=check_circular, allow_nan=allow_nan, indent=indent,
separators=separators, encoding=encoding, default=default,
sort_keys=sort_keys, **kw).encode(obj)


(2)myencoder:

"""Implementation of JSONEncoder
"""
import re
import sys

try:
from _json import encode_basestring_ascii as c_encode_basestring_ascii
except ImportError:
c_encode_basestring_ascii = None
try:
from _json import make_encoder as c_make_encoder
except ImportError:
c_make_encoder = None

ESCAPE = re.compile(r'[\x00-\x1f\\"\b\f\n\r\t]')
ESCAPE_ASCII = re.compile(r'([\\"]|[^\ -~])')
HAS_UTF8 = re.compile(r'[\x80-\xff]')
ESCAPE_DCT = {
'\\': '\\\\',
'"': '\\"',
'\b': '\\b',
'\f': '\\f',
'\n': '\\n',
'\r': '\\r',
'\t': '\\t',
}
# for i in range(0x20):
#     ESCAPE_DCT.setdefault(chr(i), '\\u{0:04x}'.format(i))
#     #ESCAPE_DCT.setdefault(chr(i), '\\u%04x' % (i,))

# INFINITY = float('inf')
INFINITY = 123456789
FLOAT_REPR = repr

def encode_basestring(s):
"""Return a JSON representation of a Python string

"""
def replace(match):
return ESCAPE_DCT[match.group(0)]
return '"' + ESCAPE.sub(replace, s) + '"'

def py_encode_basestring_ascii(s):
"""Return an ASCII-only JSON representation of a Python string

"""
if isinstance(s, str) and HAS_UTF8.search(s) is not None:
s = s.decode('utf-8')
def replace(match):
s = match.group(0)
try:
return ESCAPE_DCT[s]
except KeyError:
n = ord(s)
if n < 0x10000:
#                 return '\\u{0:04x}'.format(n)
return '\\u%04x' % (n,)
else:
# surrogate pair
n -= 0x10000
s1 = 0xd800 | ((n >> 10) & 0x3ff)
s2 = 0xdc00 | (n & 0x3ff)
#                 return '\\u{0:04x}\\u{1:04x}'.format(s1, s2)
return '\\u%04x\\u%04x' % (s1, s2)
return '"' + str(ESCAPE_ASCII.sub(replace, s)) + '"'

encode_basestring_ascii = (
c_encode_basestring_ascii or py_encode_basestring_ascii)

class JSONEncoder(object):
"""Extensible JSON <http://json.org> encoder for Python data structures.

Supports the following objects and types by default:

+-------------------+---------------+
| Python            | JSON          |
+===================+===============+
| dict              | object        |
+-------------------+---------------+
| list, tuple       | array         |
+-------------------+---------------+
| str, unicode      | string        |
+-------------------+---------------+
| int, long, float  | number        |
+-------------------+---------------+
| True              | true           |
+-------------------+---------------+
| False             | false         |
+-------------------+---------------+
| None              | null          |
+-------------------+---------------+

To extend this to recognize other objects, subclass and implement a
``.default()`` method with another method that returns a serializable
object for ``o`` if possible, otherwise it should call the superclass
implementation (to raise ``TypeError``).

"""
item_separator = ', '
key_separator = ': '
def __init__(self, skipkeys=False, ensure_ascii=True,
check_circular=True, allow_nan=True, sort_keys=False,
indent=None, separators=None, encoding='utf-8', default=None):
"""Constructor for JSONEncoder, with sensible defaults.

If skipkeys is false, then it is a TypeError to attempt
encoding of keys that are not str, int, long, float or None.  If
skipkeys is True, such items are simply skipped.

If *ensure_ascii* is true (the default), all non-ASCII
characters in the output are escaped with \uXXXX sequences,
and the results are str instances consisting of ASCII
characters only.  If ensure_ascii is False, a result may be a
unicode instance.  This usually happens if the input contains
unicode strings or the *encoding* parameter is used.

If check_circular is true, then lists, dicts, and custom encoded
objects will be checked for circular references during encoding to
prevent an infinite recursion (which would cause an OverflowError).
Otherwise, no such check takes place.

If allow_nan is true, then NaN, Infinity, and -Infinity will be
encoded as such.  This behavior is not JSON specification compliant,
but is consistent with most JavaScript based encoders and decoders.
Otherwise, it will be a ValueError to encode such floats.

If sort_keys is true, then the output of dictionaries will be
sorted by key; this is useful for regression tests to ensure
that JSON serializations can be compared on a day-to-day basis.

If indent is a non-negative integer, then JSON array
elements and object members will be pretty-printed with that
indent level.  An indent level of 0 will only insert newlines.
None is the most compact representation.  Since the default
item separator is ', ',  the output might include trailing
whitespace when indent is specified.  You can use
separators=(',', ': ') to avoid this.

If specified, separators should be a (item_separator, key_separator)
tuple.  The default is (', ', ': ').  To get the most compact JSON
representation you should specify (',', ':') to eliminate whitespace.

If specified, default is a function that gets called for objects
that can't otherwise be serialized.  It should return a JSON encodable
version of the object or raise a ``TypeError``.

If encoding is not None, then all input strings will be
transformed into unicode using that encoding prior to JSON-encoding.
The default is UTF-8.

"""

self.skipkeys = skipkeys
self.ensure_ascii = ensure_ascii
self.check_circular = check_circular
self.allow_nan = allow_nan
self.sort_keys = sort_keys
self.indent = indent
if separators is not None:
self.item_separator, self.key_separator = separators
if default is not None:
self.default = default
self.encoding = encoding

def default(self, o):
"""Implement this method in a subclass such that it returns
a serializable object for ``o``, or calls the base implementation
(to raise a ``TypeError``).

For example, to support arbitrary iterators, you could
implement default like this::

def default(self, o):
try:
iterable = iter(o)
except TypeError:
pass
else:
return list(iterable)
# Let the base class default method raise the TypeError
return JSONEncoder.default(self, o)

"""
raise TypeError(repr(o) + " is not JSON serializable")

def encode(self, o):
"""Return a JSON string representation of a Python data structure.

>>> JSONEncoder().encode({"foo": ["bar", "baz"]})
'{"foo": ["bar", "baz"]}'

"""
# This is for extremely simple cases and benchmarks.
if isinstance(o, basestring):
if isinstance(o, str):
_encoding = self.encoding
if (_encoding is not None
and not (_encoding == 'utf-8')):
o = o.decode(_encoding)
if self.ensure_ascii:
return encode_basestring_ascii(o)
else:
return encode_basestring(o)
# This doesn't pass the iterator directly to ''.join() because the
# exceptions aren't as detailed.  The list call should be roughly
# equivalent to the PySequence_Fast that ''.join() would do.
chunks = self.iterencode(o, _one_shot=True)
if not isinstance(chunks, (list, tuple)):
chunks = list(chunks)
return ''.join(chunks)

def iterencode(self, o, _one_shot=False):
"""Encode the given object and yield each string
representation as available.

For example::

for chunk in JSONEncoder().iterencode(bigobject):
mysocket.write(chunk)

"""
if self.check_circular:
markers = {}
else:
markers = None
if self.ensure_ascii:
_encoder = encode_basestring_ascii
else:
_encoder = encode_basestring
if self.encoding != 'utf-8':
def _encoder(o, _orig_encoder=_encoder, _encoding=self.encoding):
if isinstance(o, str):
o = o.decode(_encoding)
return _orig_encoder(o)

def floatstr(o, allow_nan=self.allow_nan,
_repr=FLOAT_REPR, _inf=INFINITY, _neginf=-INFINITY):
# Check for specials.  Note that this type of test is processor
# and/or platform-specific, so do tests which don't depend on the
# internals.

if o != o:
text = 'NaN'
elif o == _inf:
text = 'Infinity'
elif o == _neginf:
text = '-Infinity'
else:
return _repr(o)

if not allow_nan:
raise ValueError(
"Out of range float values are not JSON compliant: " +
repr(o))

return text

if (_one_shot and c_make_encoder is not None
and self.indent is None and not self.sort_keys):
_iterencode = c_make_encoder(
markers, self.default, _encoder, self.indent,
self.key_separator, self.item_separator, self.sort_keys,
self.skipkeys, self.allow_nan)
else:
_iterencode = _make_iterencode(
markers, self.default, _encoder, self.indent, floatstr,
self.key_separator, self.item_separator, self.sort_keys,
self.skipkeys, _one_shot)
return _iterencode(o, 0)

def _make_iterencode(markers, _default, _encoder, _indent, _floatstr,
_key_separator, _item_separator, _sort_keys, _skipkeys, _one_shot,
## HACK: hand-optimized bytecode; turn globals into locals
ValueError=ValueError,
basestring=basestring,
dict=dict,
float=float,
id=id,
int=int,
isinstance=isinstance,
list=list,
long=long,
str=str,
tuple=tuple,
):

def _iterencode_list(lst, _current_indent_level):
if not lst:
yield '[]'
return
if markers is not None:
markerid = id(lst)
if markerid in markers:
raise ValueError("Circular reference detected")
markers[markerid] = lst
buf = '['
if _indent is not None:
_current_indent_level += 1
newline_indent = '\n' + (' ' * (_indent * _current_indent_level))
separator = _item_separator + newline_indent
buf += newline_indent
else:
newline_indent = None
separator = _item_separator
first = True
for value in lst:
if first:
first = False
else:
buf = separator
if isinstance(value, basestring):
yield buf + _encoder(value)
elif value is None:
yield buf + 'null'
elif value is True:
yield buf + 'true'
elif value is False:
yield buf + 'false'
elif isinstance(value, (int, long)):
yield buf + str(value)
elif isinstance(value, float):
yield buf + _floatstr(value)
else:
yield buf
if isinstance(value, (list, tuple)):
chunks = _iterencode_list(value, _current_indent_level)
elif isinstance(value, dict):
chunks = _iterencode_dict(value, _current_indent_level)
else:
chunks = _iterencode(value, _current_indent_level)
for chunk in chunks:
yield chunk
if newline_indent is not None:
_current_indent_level -= 1
yield '\n' + (' ' * (_indent * _current_indent_level))
yield ']'
if markers is not None:
del markers[markerid]

def _iterencode_dict(dct, _current_indent_level):
if not dct:
yield '{}'
return
if markers is not None:
markerid = id(dct)
if markerid in markers:
raise ValueError("Circular reference detected")
markers[markerid] = dct
yield '{'
if _indent is not None:
_current_indent_level += 1
newline_indent = '\n' + (' ' * (_indent * _current_indent_level))
item_separator = _item_separator + newline_indent
yield newline_indent
else:
newline_indent = None
item_separator = _item_separator
first = True
if _sort_keys:
items = sorted(dct.items(), key=lambda kv: kv[0])
else:
items = dct.iteritems()
for key, value in items:
if isinstance(key, basestring):
pass
# JavaScript is weakly typed for these, so it makes sense to
# also allow them.  Many encoders seem to do something like this.
elif isinstance(key, float):
key = _floatstr(key)
elif key is True:
key = 'true'
elif key is False:
key = 'false'
elif key is None:
key = 'null'
elif isinstance(key, (int, long)):
key = str(key)
elif _skipkeys:
continue
else:
raise TypeError("key " + repr(key) + " is not a string")
if first:
first = False
else:
yield item_separator
yield _encoder(key)
yield _key_separator
if isinstance(value, basestring):
yield _encoder(value)
elif value is None:
yield 'null'
elif value is True:
yield 'true'
elif value is False:
yield 'false'
elif isinstance(value, (int, long)):
yield str(value)
elif isinstance(value, float):
yield _floatstr(value)
else:
if isinstance(value, (list, tuple)):
chunks = _iterencode_list(value, _current_indent_level)
elif isinstance(value, dict):
chunks = _iterencode_dict(value, _current_indent_level)
else:
chunks = _iterencode(value, _current_indent_level)
for chunk in chunks:
yield chunk
if newline_indent is not None:
_current_indent_level -= 1
yield '\n' + (' ' * (_indent * _current_indent_level))
yield '}'
if markers is not None:
del markers[markerid]

def _iterencode(o, _current_indent_level):
if isinstance(o, basestring):
yield _encoder(o)
elif o is None:
yield 'null'
elif o is True:
yield 'true'
elif o is False:
yield 'false'
elif isinstance(o, (int, long)):
yield str(o)
elif isinstance(o, float):
yield _floatstr(o)
elif isinstance(o, (list, tuple)):
for chunk in _iterencode_list(o, _current_indent_level):
yield chunk
elif isinstance(o, dict):
for chunk in _iterencode_dict(o, _current_indent_level):
yield chunk
else:
if markers is not None:
markerid = id(o)
if markerid in markers:
raise ValueError("Circular reference detected")
markers[markerid] = o
o = _default(o)
for chunk in _iterencode(o, _current_indent_level):
yield chunk
if markers is not None:
del markers[markerid]

return _iterencode


这样就可以使用我们自己写的json类了:

# -*- coding: utf-8 -*-
import myJson
dicts = {"a":"中文","b":2}
jsonStr = myJson.dumps(dicts,ensure_ascii=False)
print jsonStr
输出结果:

{"a": "中文", "b": 2}

在扒这函数中用的笨方法是先把2.7版本的源码拷下来,然后电脑上再装python2.5版本的,然后根据编译器报的错一点一点修改,就搞定了。其他的函数我想应该也差不多这么做就能实现,但是因为没用到,就不花时间去扒了。
内容来自用户分享和网络整理,不保证内容的准确性,如有侵权内容,可联系管理员处理 点击这里给我发消息
标签: