1.命令介绍

最近学习并使用了一个python的内置函数dir，首先help一下：

复制代码 代码如下:
>>> help(dir)
Help on built-in function dir in module __builtin__:

dir()
    dir([object]) -> list of strings

    Return an alphabetized list of names comprising (some of) the attributes
    of the given object, and of attributes reachable from it:

    No argument:  the names in the current scope.
    Module object:  the module attributes.
    Type or class object:  its attributes, and recursively the attributes of
        its bases.
    Otherwise:  its attributes, its class\’s attributes, and recursively the
        attributes of its class\’s base classes.

通过help，可以简单的认为dir列出指定对象或类的属性。
2.实例
下面是一个简单的测试：
复制代码 代码如下:
 class A:
     def a(self):
         pass
 
 
 class A1(A):
    def a1(self):
        pass

if __name__ == \’__main__\’:
    print(\”dir without arguments:\”, dir())
    print(\”dir class A:\”, dir(A))
    print(\”dir class A1:\”, dir(A1))
    a = A1()
    print(\”dir object a(A1):\”, dir(a))
    print(\”dir function a.a:\”, dir(a.a))

测试结果：
复制代码 代码如下:
dir without arguments: [\’A\’, \’A1\’, \’__builtins__\’, \’__doc__\’, \’__file__\’, \’__name__\’, \’__package__\’]
dir class A: [\’__class__\’, \’__delattr__\’, \’__dict__\’, \’__doc__\’, \’__eq__\’, \’__format__\’, \’__ge__\’, \’__getattribute__\’, \’__gt__\’, \’__hash__\’, \’__init__\’, \’__le__\’, \’__lt__\’, \’__module__\’, \’__ne__\’, \’__new__\’, \’__reduce__\’, \’__reduce_ex__\’, \’__repr__\’, \’__setattr__\’, \’__sizeof__\’, \’__str__\’, \’__subclasshook__\’, \’__weakref__\’, \’a\’]
dir class A1: [\’__class__\’, \’__delattr__\’, \’__dict__\’, \’__doc__\’, \’__eq__\’, \’__format__\’, \’__ge__\’, \’__getattribute__\’, \’__gt__\’, \’__hash__\’, \’__init__\’, \’__le__\’, \’__lt__\’, \’__module__\’, \’__ne__\’, \’__new__\’, \’__reduce__\’, \’__reduce_ex__\’, \’__repr__\’, \’__setattr__\’, \’__sizeof__\’, \’__str__\’, \’__subclasshook__\’, \’__weakref__\’, \’a\’, \’a1\’]
dir object a(A1): [\’__class__\’, \’__delattr__\’, \’__dict__\’, \’__doc__\’, \’__eq__\’, \’__format__\’, \’__ge__\’, \’__getattribute__\’, \’__gt__\’, \’__hash__\’, \’__init__\’, \’__le__\’, \’__lt__\’, \’__module__\’, \’__ne__\’, \’__new__\’, \’__reduce__\’, \’__reduce_ex__\’, \’__repr__\’, \’__setattr__\’, \’__sizeof__\’, \’__str__\’, \’__subclasshook__\’, \’__weakref__\’, \’a\’, \’a1\’]
dir function a.a: [\’__call__\’, \’__class__\’, \’__delattr__\’, \’__doc__\’, \’__eq__\’, \’__format__\’, \’__func__\’, \’__ge__\’, \’__get__\’, \’__getattribute__\’, \’__gt__\’, \’__hash__\’, \’__init__\’, \’__le__\’, \’__lt__\’, \’__ne__\’, \’__new__\’, \’__reduce__\’, \’__reduce_ex__\’, \’__repr__\’, \’__self__\’, \’__setattr__\’, \’__sizeof__\’, \’__str__\’, \’__subclasshook__\’]

3.使用dir查找module下的所有类
最初使用这个函数的初衷，就是在一个module中查找实现的类名，通过该函数可以很容易的实现。
比如把上面的测试程序保存为A.py，再建一个测试程序，内容如下：
复制代码 代码如下:
import A

if __name__ == \’__main__\’:
    print(\”dir module A:\”, dir(A))

结果如下：
复制代码 代码如下:
dir module A: [\’A\’, \’A1\’, \’__builtins__\’, \’__doc__\’, \’__file__\’, \’__name__\’, \’__package__\’]

可以看出class A和A1都能够找到。

4.如何找到当前模块下的类

这是一个烦恼较长时间的一个问题，也没有搜到详细的解决方法，下面是我的集中实现方法。

4.1.方法一：在module下面直接调用

比如在上面的A.py最下面添加一行，即可在后续的代码中可以使用selfDir来查找当前的module下的类，修改后的代码如下：

复制代码 代码如下:
 class A:
     def a(self):
         pass
 
 class A1(A):
     def a1(self):
         pass
 
 curModuleDir=dir()  # get dir of current file(module)

if __name__ == \’__main__\’:
    print(\”dir without arguments:\”, dir())
    print(\”dir class A:\”, dir(A))
    print(\”dir class A1:\”, dir(A1))
    a = A1()
    print(\”dir object a(A1):\”, dir(a))
    print(\”dir function a.a:\”, dir(a.a))
    print(\”dir current file:\”, curModuleDir)

4.2.方法二：import当前module
把当前module和别的import一样引用，代码如下：

复制代码 代码如下:
 # A.py
 import A as this # import current module
 
 class A:
     def a(self):
         pass
 
 class A1(A):
     def a1(self):
        pass

if __name__ == \’__main__\’:
    print(\”dir without arguments:\”, dir())
    print(\”dir class A:\”, dir(A))
    print(\”dir class A1:\”, dir(A1))
    a = A1()
    print(\”dir object a(A1):\”, dir(a))
    print(\”dir function a.a:\”, dir(a.a))
    print(\”dir current file:\”, dir(this))

4.3.方法三：根据module名称查找module，然后调用dir
我们知道module下面有个属性__name__显示module名称，怎么能够根据module名称来查找module对象呢？可以借助sys.modules。代码如下：
复制代码 代码如下:
import sys

class A:
    def a(self):
        pass

class A1(A):
    def a1(self):
        pass

if __name__ == \’__main__\’:
    print(\”dir without arguments:\”, dir())
    print(\”dir class A:\”, dir(A))
    print(\”dir class A1:\”, dir(A1))
    a = A1()
    print(\”dir object a(A1):\”, dir(a))
    print(\”dir function a.a:\”, dir(a.a))
    print(\”dir current file:\”, dir(sys.modules[__name__])) # 使用__name__获取当前module对象，然后使用对象获得dir