python中3个帮助函数help，di

>>> help("modules")

Please wait a moment while I gather a list of all available modules...

BaseHTTPServer      array               htmllib             sets
Bastion             ast                 httplib             sgmllib
CDROM               asynchat            ihooks              sha
CGIHTTPServer       asyncore            imaplib             shelve
Canvas              atexit              imghdr              shlex
ConfigParser        audiodev            imp                 shutil
Cookie              audioop             importlib           signal
DLFCN               axi                 imputil             site
Dialog              base64              inspect             sitecustomize
DocXMLRPCServer     bdb                 io                  smtpd
FileDialog          binascii            itertools           smtplib

>>> help("json")
Help on package json:

NAME
    json

FILE
    /usr/lib/python2.7/json/__init__.py

MODULE DOCS
    http://docs.python.org/library/json

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::

>>> 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             |

>>> 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.

>>> 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']

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