序列化说的简单点，就是把python的数据类型转为json的字符串，而反序列化就是把json的字符串转为
python的数据类型。python的数据类型分别是list,tuple,dict，下面通过实际的案例，来说明把list,tuple,dict如何
的进行序列化和反序列化，实现这个过程的，就是今天要说的主角色json库，我们先来看json库使用到的方法
以及详细的help信息，见代码：
#!/usr/bin/env python #-*- coding:utf-8 -*- import json print dir(json) print type(help(json))
见执行如上代码后控制台的输出内容：
C:\Python27\python.exe D:/git/Python/FullStack/share/jsonTest.py ['JSONDecoder', 'JSONEncoder', '__all__', '__author__', '__builtins__', '__doc__', '__file__', '__name__', '__package__', '__path__', '__version__', '_default_decoder', '_default_encoder', 'decoder', 'dump', 'dumps', 'encoder', 'load', 'loads', 'scanner'] Help on package json: NAME json FILE c:\python27\lib\json\__init__.py DESCRIPTION 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) PACKAGE CONTENTS decoder encoder scanner tests (package) tool CLASSES __builtin__.object json.decoder.JSONDecoder json.encoder.JSONEncoder class JSONDecoder(__builtin__.object) | Simple JSON <http://json.org> decoder | | Performs the following translations in decoding by default: | | +---------------+-------------------+ | | JSON | Python | | +===============+===================+ | | object | dict | | +---------------+-------------------+ | | array | list | | +---------------+-------------------+ | | string | unicode | | +---------------+-------------------+ | | number (int) | int, long | | +---------------+-------------------+ | | number (real) | float | | +---------------+-------------------+ | | true | True | | +---------------+-------------------+ | | false | False | | +---------------+-------------------+ | | null | None | | +---------------+-------------------+ | | It also understands ``NaN``, ``Infinity``, and ``-Infinity`` as | their corresponding ``float`` values, which is outside the JSON spec. | | Methods defined here: | | __init__(self, encoding=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, strict=True, object_pairs_hook=None) | ``encoding`` determines the encoding used to interpret any ``str`` | objects decoded by this instance (utf-8 by default). It has no | effect when decoding ``unicode`` objects. | | Note that currently only encodings that are a superset of ASCII work, | strings of other encodings should be passed in as ``unicode``. | | ``object_hook``, if specified, will be called with the result | of every JSON object decoded and its return value will be used in | place of the given ``dict``. This can be used to provide custom | deserializations (e.g. to support JSON-RPC class hinting). | | ``object_pairs_hook``, if specified will be called with the result of | every JSON object decoded with an ordered list of pairs. The return | value of ``object_pairs_hook`` will be used instead of the ``dict``. | This feature can be used to implement custom decoders that rely on the | order that the key and value pairs are decoded (for example, | collections.OrderedDict will remember the order of insertion). If | ``object_hook`` is also defined, the ``object_pairs_hook`` takes | priority. | | ``parse_float``, if specified, will be called with the string | of every JSON float to be decoded. By default this is equivalent to | float(num_str). This can be used to use another datatype or parser | for JSON floats (e.g. decimal.Decimal). | | ``parse_int``, if specified, will be called with the string | of every JSON int to be decoded. By default this is equivalent to | int(num_str). This can be used to use another datatype or parser | for JSON integers (e.g. float). | | ``parse_constant``, if specified, will be called with one of the | following strings: -Infinity, Infinity, NaN. | This can be used to raise an exception if invalid JSON numbers | are encountered. | | If ``strict`` is false (true is the default), then control | characters will be allowed inside strings. Control characters in | this context are those with character codes in the 0-31 range, | including ``'\t'`` (tab), ``'\n'``, ``'\r'`` and ``'\0'``. | | decode(self, s, _w=<built-in method match of _sre.SRE_Pattern object>) | Return the Python representation of ``s`` (a ``str`` or ``unicode`` | instance containing a JSON document) | | raw_decode(self, s, idx=0) | Decode a JSON document from ``s`` (a ``str`` or ``unicode`` | beginning with a JSON document) and return a 2-tuple of the Python | representation and the index in ``s`` where the document ended. | | This can be used to decode a JSON document from a string that may | have extraneous data at the end. | | ---------------------------------------------------------------------- | Data descriptors defined here: | | __dict__ | dictionary for instance variables (if defined) | | __weakref__ | list of weak references to the object (if defined) class JSONEncoder(__builtin__.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``). | | Methods defined here: | | __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. | | 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) | | encode(self, o) | Return a JSON string representation of a Python data structure. | | >>> JSONEncoder().encode({"foo": ["bar", "baz"]}) | '{"foo": ["bar", "baz"]}' | | 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) | | ---------------------------------------------------------------------- | Data descriptors defined here: | | __dict__ | dictionary for instance variables (if defined) | | __weakref__ | list of weak references to the object (if defined) | | ---------------------------------------------------------------------- | Data and other attributes defined here: | | item_separator = ', ' | | key_separator = ': ' FUNCTIONS dump(obj, fp, 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`` as a JSON formatted stream to ``fp`` (a ``.write()``-supporting file-like object). If ``skipkeys`` is true 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 true (the default), all non-ASCII characters in the output are escaped with ``\uXXXX`` sequences, and the result is a ``str`` instance consisting of ASCII characters only. If ``ensure_ascii`` is ``False``, some chunks written to ``fp`` may be ``unicode`` instances. This usually happens because the input contains unicode strings or the ``encoding`` parameter is used. Unless ``fp.write()`` explicitly understands ``unicode`` (as in ``codecs.getwriter``) this is likely to cause an error. 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. 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 true 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. load(fp, encoding=None, cls=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, object_pairs_hook=None, **kw) Deserialize ``fp`` (a ``.read()``-supporting file-like object containing a JSON document) to a Python object. If the contents of ``fp`` is encoded with an ASCII based encoding other than utf-8 (e.g. latin-1), then an appropriate ``encoding`` name must be specified. Encodings that are not ASCII based (such as UCS-2) are not allowed, and should be wrapped with ``codecs.getreader(fp)(encoding)``, or simply decoded to a ``unicode`` object and passed to ``loads()`` ``object_hook`` is an optional function that will be called with the result of any object literal decode (a ``dict``). The return value of ``object_hook`` will be used instead of the ``dict``. This feature can be used to implement custom decoders (e.g. JSON-RPC class hinting). ``object_pairs_hook`` is an optional function that will be called with the result of any object literal decoded with an ordered list of pairs. The return value of ``object_pairs_hook`` will be used instead of the ``dict``. This feature can be used to implement custom decoders that rely on the order that the key and value pairs are decoded (for example, collections.OrderedDict will remember the order of insertion). If ``object_hook`` is also defined, the ``object_pairs_hook`` takes priority. To use a custom ``JSONDecoder`` subclass, specify it with the ``cls`` kwarg; otherwise ``JSONDecoder`` is used. loads(s, encoding=None, cls=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, object_pairs_hook=None, **kw) Deserialize ``s`` (a ``str`` or ``unicode`` instance containing a JSON document) to a Python object. If ``s`` is a ``str`` instance and is encoded with an ASCII based encoding other than utf-8 (e.g. latin-1) then an appropriate ``encoding`` name must be specified. Encodings that are not ASCII based (such as UCS-2) are not allowed and should be decoded to ``unicode`` first. ``object_hook`` is an optional function that will be called with the result of any object literal decode (a ``dict``). The return value of ``object_hook`` will be used instead of the ``dict``. This feature can be used to implement custom decoders (e.g. JSON-RPC class hinting). ``object_pairs_hook`` is an optional function that will be called with the result of any object literal decoded with an ordered list of pairs. The return value of ``object_pairs_hook`` will be used instead of the ``dict``. This feature can be used to implement custom decoders that rely on the order that the key and value pairs are decoded (for example, collections.OrderedDict will remember the order of insertion). If ``object_hook`` is also defined, the ``object_pairs_hook`` takes priority. ``parse_float``, if specified, will be called with the string of every JSON float to be decoded. By default this is equivalent to float(num_str). This can be used to use another datatype or parser for JSON floats (e.g. decimal.Decimal). ``parse_int``, if specified, will be called with the string of every JSON int to be decoded. By default this is equivalent to int(num_str). This can be used to use another datatype or parser for JSON integers (e.g. float). ``parse_constant``, if specified, will be called with one of the following strings: -Infinity, Infinity, NaN, null, true, false. This can be used to raise an exception if invalid JSON numbers are encountered. To use a custom ``JSONDecoder`` subclass, specify it with the ``cls`` kwarg; otherwise ``JSONDecoder`` is used. DATA __all__ = ['dump', 'dumps', 'load', 'loads', 'JSONDecoder', 'JSONEncod... __author__ = 'Bob Ippolito <[email protected]>' __version__ = '2.0.9' VERSION 2.0.9 AUTHOR Bob Ippolito <[email protected]> <type 'NoneType'> Process finished with exit code 0
控制台输出的内容很丰富，事实上，我们经常使用的json模块的方法为：dumps(),loads(),dump(),load(),其中dump()和load()是对文件的
操作以及处理，我们先通过实际的案例代码，来看dumps(),loads()对序列化和反序列化的处理，见代码：
#!/usr/bin/env python #-*- coding:utf-8 -*- import json print dir(json) print type(help(json)) list1=[1,2,3,4,5] tuple=('wuya','age','address') dict={'name':'wuya','age':20,'address':'xian'} print u'对列表进行序列化:',json.dumps(list1) print u'序列化后的类型:',type(json.dumps(list1)) print u'对list序列化后的内容进行反序列化:',json.loads(json.dumps(list1)) print u'类型:',type(json.loads(json.dumps(list1))) print u'对元组进行序列化:',json.dumps(tuple) print u'序列化后的类型:',type(json.dumps(tuple)) print u'对tuple序列化后的内容进行反序列化:',json.loads(json.dumps(tuple)) print u'类型:',type(json.loads(json.dumps(tuple))) print u'对字典进行序列化:',json.dumps(dict) print u'序列化后的类型:',type(json.dumps(dict)) print u'对dict序列化后的内容进行反序列化:',json.loads(json.dumps(dict)) print u'类型:',type(json.loads(json.dumps(dict)))
如上的代码看起来比较繁琐，我们对代码进行下重构，让代码看起来更加的简单，见重构后的代码：
def jsonTest(*args,**kwargs): '''序列化和反序列化''' # if isinstance() if isinstance(args,list) or isinstance(args,tuple): str_json=json.dumps(args) print u'序列化后的数据类型:',type(str_json),u'内容:',str_json type_json=json.loads(str_json) print u'反序列化后的数据类型:',type(type_json),u'内容:',type_json else: str_json=json.dumps(kwargs) print u'序列化后的数据类型:',type(str_json),u'内容:',str_json type_json=json.loads(str_json) print u'反序列化后的数据类型:',type(type_json),u'内容:',type_json
下面我们来看load()与dump()方法的使用，也就是对文件的操作，实现的方式是先把数据写入文件中，然后进行序列化和
反序列化的操作，见实现的代码：
#!/usr/bin/env python #-*- coding:utf-8 -*- import json accounts={ 10: { 'name':'wuya', 'sex':'boy', 'address':'xian' } } def json_file(): #把内容入文件 with open('log.json','w') as f1: f1.write(json.dumps(accounts)) #对文件的内容进行反序列化 with open('log.json','r') as f2: type_json=json.load(f2) print u'反序列化后的内容:',type_json,u'类型:',type(type_json) #修改文件内容 type_json['age']=20 #修改后的内容写入到文件中 json.dump(type_json,open('log.json','w')) if __name__ == '__main__': json_file()
见操作后的log.json文件内容：
{"10": {"sex": "boy", "name": "wuya", "address": "xian"}, "age": 20}