内置函数 dir() 用于按模块名搜索模块定义，它返回一个字符串类型的存储列表:
>>> import fibo, sys
>>> dir(fibo)
["__name__", "fib", "fib2"]
>>> dir(sys)
["__displayhook__", "__doc__", "__excepthook__", "__name__", "__stderr__",
"__stdin__", "__stdout__", "_getframe", "api_version", "argv",
"builtin_module_names", "byteorder", "callstats", "copyright",
"displayhook", "exc_info", "excepthook",
"exec_prefix", "executable", "exit", "getdefaultencoding", "getdlopenflags",
"getrecursionlimit", "getrefcount", "hexversion", "maxint", "maxunicode",
"meta_path", "modules", "path", "path_hooks", "path_importer_cache",
"platform", "prefix", "ps1", "ps2", "setcheckinterval", "setdlopenflags",
"setprofile", "setrecursionlimit", "settrace", "stderr", "stdin", "stdout",
"version", "version_info", "warnoptions"]
无参数调用时，dir() 函数返回当前定义的命名:
>>> a = [1, 2, 3, 4, 5]
>>> import fibo
>>> fib = fibo.fib
>>> dir()
["__builtins__", "__doc__", "__file__", "__name__", "a", "fib", "fibo", "sys"]
注意该列表列出了所有类型的名称：变量，模块，函数，等等。
dir() 不会列出内置函数和变量名。如果你想列出这些内容，它们在标准模块 builtin 中定义:
>>> import builtins
>>> dir(builtins)
["ArithmeticError", "AssertionError", "AttributeError", "BaseException", "Buffer
Error", "BytesWarning", "DeprecationWarning", "EOFError", "Ellipsis", "Environme
ntError", "Exception", "False", "FloatingPointError", "FutureWarning", "Generato
rExit", "IOError", "ImportError", "ImportWarning", "IndentationError", "IndexErr
or", "KeyError", "KeyboardInterrupt", "LookupError", "MemoryError", "NameError",
"None", "NotImplemented", "NotImplementedError", "OSError", "OverflowError", "P
endingDeprecationWarning", "ReferenceError", "RuntimeError", "RuntimeWarning", "
StopIteration", "SyntaxError", "SyntaxWarning", "SystemError", "SystemExit", "Ta
bError", "True", "TypeError", "UnboundLocalError", "UnicodeDecodeError", "Unicod
eEncodeError", "UnicodeError", "UnicodeTranslateError", "UnicodeWarning", "UserW
arning", "ValueError", "Warning", "ZeroDivisionError", "__build_class__", "__deb
ug__", "__doc__", "__import__", "__name__", "__package__", "abs", "all", "any",
"ascii", "bin", "bool", "bytearray", "bytes", "chr", "classmethod", "compile", "
complex", "copyright", "credits", "delattr", "dict", "dir", "divmod", "enumerate
", "eval", "exec", "exit", "filter", "float", "format", "frozenset", "getattr",
"globals", "hasattr", "hash", "help", "hex", "id", "input", "int", "isinstance",
"issubclass", "iter", "len", "license", "list", "locals", "map", "max", "memory
view", "min", "next", "object", "oct", "open", "ord", "pow", "print", "property"
, "quit", "range", "repr", "reversed", "round", "set", "setattr", "slice", "sort
ed", "staticmethod", "str", "sum", "super", "tuple", "type", "vars", "zip"]