1.命令介紹
最近學(xué)習(xí)并使用了一個(gè)python的內(nèi)置函數(shù)dir，首先help一下：
>>> 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.
通過(guò)help，可以簡(jiǎn)單的認(rèn)為dir列出指定對(duì)象或類的屬性。
2.實(shí)例
下面是一個(gè)簡(jiǎn)單的測(cè)試：
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))
測(cè)試結(jié)果：
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下的所有類
最初使用這個(gè)函數(shù)的初衷，就是在一個(gè)module中查找實(shí)現(xiàn)的類名，通過(guò)該函數(shù)可以很容易的實(shí)現(xiàn)。
比如把上面的測(cè)試程序保存為A.py，再建一個(gè)測(cè)試程序，內(nèi)容如下：
import A
if __name__ == '__main__':
print("dir module A:", dir(A))
結(jié)果如下：
dir module A: ['A', 'A1', '__builtins__', '__doc__', '__file__', '__name__', '__package__']
可以看出class A和A1都能夠找到。
4.如何找到當(dāng)前模塊下的類
這是一個(gè)煩惱較長(zhǎng)時(shí)間的一個(gè)問(wèn)題，也沒(méi)有搜到詳細(xì)的解決方法，下面是我的集中實(shí)現(xiàn)方法。
4.1.方法一：在module下面直接調(diào)用
比如在上面的A.py最下面添加一行，即可在后續(xù)的代碼中可以使用selfDir來(lái)查找當(dāng)前的module下的類，修改后的代碼如下：
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當(dāng)前module
把當(dāng)前module和別的import一樣引用，代碼如下：
# 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：根據(jù)module名稱查找module，然后調(diào)用dir
我們知道m(xù)odule下面有個(gè)屬性__name__顯示module名稱，怎么能夠根據(jù)module名稱來(lái)查找module對(duì)象呢？可以借助sys.modules。代碼如下：
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__獲取當(dāng)前module對(duì)象，然后使用對(duì)象獲得dir
