Python built-in functions dir explanation

1. Command Introduction

Recently learned and used a python built-in function, dir, first help:
Copy the Code code as follows:

>>> 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.

With help, you can simply assume that dir lists the properties of the specified object or class.
2. Example
The following is a simple test:
Copy CodeThe code is as follows:

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))

Test results:
Copy CodeThe code is as follows:

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__ ', ' __ge ' T__ ', ' __getattribute__ ', ' __gt__ ', ' __hash__ ', ' __init__ ', ' __le__ ', ' __lt__ ', ' __ne__ ', ' __new__ ', ' __reduce__ ', ' __ Reduce_ex__ ', ' __repr__ ', ' __self__ ', ' __setattr__ ', ' __sizeof__ ', ' __str__ ', ' __subclasshook__ '

3. Use Dir to find all classes under module
The original intention of using this function is to find the implemented class name in a module, which can be easily implemented by this function.
For example, to save the above test program as a.py, and then build a test program, the contents are as follows:
Copy CodeThe code is as follows:

Import A

if __name__ = = ' __main__ ':
Print ("dir module A:", dir (a))

The results are as follows:
Copy CodeThe code is as follows:

Dir module A: [' A ', ' A1 ', ' __builtins__ ', ' __doc__ ', ' __file__ ', ' __name__ ', ' __package__ ']

You can see that both Class A and A1 can be found.

4. How to find the class under the current module

This is a problem for a long time, and did not search for a detailed solution, the following is my centralized implementation method.

4.1. Method One: Call directly below the module

For example, in the above a.py to add a row, you can use Selfdir in subsequent code to find the current module under the class, the modified code is as follows:
Copy the Code code as follows:

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. Method Two: Import current module
Refer to the current module as in the other import code as follows:
Copy the Code code as follows:

# a.py
Import A as this # import the 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. Method Three: Find the module by module name and then call dir
We know that the module has a property __name__ shows the module name, how can we find the module object according to the module name? You can use Sys.modules. The code is as follows:
Copy CodeThe code is as follows:

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__])) # Use __name__ to get the current module object and then use the object to get dir

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