python中3个帮助函数help，dir，type的使用

1 help函数：查看模块、函数、变量的详细说明：

• 查看模块

>>> help("modules")Please wait a moment while I gather a list of all available modules...BaseHTTPServer      array               htmllib             setsBastion             ast                 httplib             sgmllibCDROM               asynchat            ihooks              shaCGIHTTPServer       asyncore            imaplib             shelveCanvas              atexit              imghdr              shlexConfigParser        audiodev            imp                 shutilCookie              audioop             importlib           signalDLFCN               axi                 imputil             siteDialog              base64              inspect             sitecustomizeDocXMLRPCServer     bdb                 io                  smtpdFileDialog          binascii            itertools           smtplib

• 查看包

>>> help("json")Help on package json:NAME    jsonFILE    /usr/lib/python2.7/json/__init__.pyMODULE DOCS    http://docs.python.org/library/jsonDESCRIPTION    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::

• 查看类

>>> help(json.JSONDecoder)Help on class JSONDecoder in module json.decoder: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             |

• 查看函数：

>>> help(json.dump)Help on function dump in module json: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, **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 false, then the some chunks written to ``fp``    may be ``unicode`` instances, subject to normal Python ``str`` to    ``unicode`` coercion rules. Unless ``fp.write()`` explicitly    understands ``unicode`` (as in ``codecs.getwriter()``) this is likely    to cause an error.

2 dir函数：查看变量可用的函数或方法

>>> import sys>>> dir(sys)['__displayhook__', '__doc__', '__excepthook__', '__name__', '__package__', '__stderr__', '__stdin__', '__stdout__', '_clear_type_cache', '_current_frames', '_getframe', '_mercurial', 'api_version', 'argv', 'builtin_module_names', 'byteorder', 'call_tracing', 'callstats', 'copyright', 'displayhook', 'dont_write_bytecode', 'exc_clear', 'exc_info', 'exc_type', 'excepthook', 'exec_prefix', 'executable', 'exit', 'exitfunc', 'flags', 'float_info', 'float_repr_style', 'getcheckinterval', 'getdefaultencoding', 'getdlopenflags', 'getfilesystemencoding', 'getprofile', 'getrecursionlimit', 'getrefcount', 'getsizeof', 'gettrace', 'hexversion', 'last_traceback', 'last_type', 'last_value', 'long_info', 'maxint', 'maxsize', 'maxunicode', 'meta_path', 'modules', 'path', 'path_hooks', 'path_importer_cache', 'platform', 'prefix', 'ps1', 'ps2', 'py3kwarning', 'pydebug', 'setcheckinterval', 'setdlopenflags', 'setprofile', 'setrecursionlimit', 'settrace', 'stderr', 'stdin', 'stdout', 'subversion', 'version', 'version_info', 'warnoptions']

3 type函数：查看变量的类型

<type 'module'>>>> type (json.__name__)<type 'str'>>>> type (json.decoder)<type 'module'>

4 退出python命令行

windows: ctrl+z 回车

linux：ctrl+d 

注：使用pydoc module 可查看模块的文档说明