Without arguments, return the list of names in the current local scope. With an argument, attempt to return a list of valid attributes for that object.
If the object has a method named, this method will be called and must return the list of attributes. This allows objects that implement a customorfunction to customize the wayreports their attributes.
If the object does not provide, the function tries its best to gather information from the object’s __dict__ attribute, if defined, and from its type object. The resulting list is not necessarily complete, and may be inaccurate when the object has a custom.
The defaultmechanism behaves differently with different types of objects, as it attempts to produce the most relevant, rather than complete, information:
If the object is a module object, the list contains the names of the module’s attributes. If the object is a type or class object, the list contains the names of its attributes, and recursively of the attributes of its bases. Otherwise, the list contains the object’s attributes’ names, the names of its class’s attributes, and recursively of the attributes of its class’s base classes. 说明：1. 当不传参数时，返回当前作用域内的变量、方法和定义的类型列表。
>>> dir() ['__builtins__', '__doc__', '__loader__', '__name__', '__package__', '__spec__'] >>> a = 10 #定义变量a >>> dir() #多了一个a ['__builtins__', '__doc__', '__loader__', '__name__', '__package__', '__spec__', 'a']2. 当参数对象是模块时，返回模块的属性、方法列表。
>>> import math >>> math <module 'math' (built-in)> >>> dir(math) ['__doc__', '__loader__', '__name__', '__package__', '__spec__', 'acos', 'acosh', 'asin', 'asinh', 'atan', 'atan2', 'atanh', 'ceil', 'copysign', 'cos', 'cosh', 'degrees', 'e', 'erf', 'erfc', 'exp', 'expm1', 'fabs', 'factorial', 'floor', 'fmod', 'frexp', 'fsum', 'gamma', 'gcd', 'hypot', 'inf', 'isclose', 'isfinite', 'isinf', 'isnan', 'ldexp', 'lgamma', 'log', 'log10', 'log1p', 'log2', 'modf', 'nan', 'pi', 'pow', 'radians', 'sin', 'sinh', 'sqrt', 'tan', 'tanh', 'trunc']3. 当参数对象是类时，返回类及其子类的属性、方法列表。
>>> class A: name = 'class' >>> a = A() >>> dir(a) #name是类A的属性，其他则是默认继承的object的属性、方法 ['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'name']4. 当对象定义了 __dir__方法，则返回__dir__方法的结果
>>> class B: def __dir__(self): return ['name','age'] >>> b = B() >>> dir(b) #调用 __dir__方法 ['age', 'name']