Python built-in functions dir and pythondir

Python built-in functions dir and pythondir

1. Command Introduction

Recently I learned and used a python built-in function dir. First, help:
Copy codeThe Code is 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
Its bases.
Otherwise: its attributes, its class's attributes, and recursively
Attributes of its class's base classes.

With help, you can simply think that dir lists the attributes of a specified object or class.
2. Instance
The following is a simple test:
Copy codeThe Code is as follows:
Class:
Def a (self ):
Pass
 
 
Class A1 ():
Def a1 (self ):
Pass

If _ name _ = '_ main __':
Print ("dir without arguments:", dir ())
Print ("dir class A:", dir ())
Print ("dir class A1:", dir (A1 ))
A = A1 ()
Print ("dir object a (A1):", dir ())
Print ("dir function a. a:", dir (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 _', '_ performance_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 _', '_ performance_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 _', '_ performance_ex _', '_ repr __', '_ setattr _', '_ sizeof _', '_ str _', '_ subclasshook _', '_ weakref __', 'A', 'a1']
Dir function. a: ['_ call _', '_ class _', '_ delattr _', '_ doc __', '_ eq _', '_ format _', '_ func _', '_ ge _', '_ get __', '_ getattribute _', '_ gt _', '_ hash _', '_ init _', '_ le __', '_ lt _', '_ ne _', '_ new _', '_ reduce _', '_ performance_ex __', '_ repr _', '_ self _', '_ setattr _', '_ sizeof _', '_ str __', '_ subclasshook _']

3. Use dir to find all classes in the module
The original intention of using this function was to find the implemented class name in a module, which can be easily implemented.
For example, save the above test program as A. py and create another test program. The content is as follows:
Copy codeThe Code is as follows:
Import

If _ name _ = '_ main __':
Print ("dir module A:", dir ())

The result is as follows:
Copy codeThe Code is as follows:
Dir module A: ['A', 'a1', '_ builtins _', '_ doc _', '_ file __', '_ name _', '_ package _']

We 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 that has been plagued for a long time, and no detailed solution has been found. The following is my Centralized implementation method.

4. 1. Method 1: directly call

For example, if you add A line at the bottom of A. py above, you can use selfDir in subsequent code to find the classes in the current module. The modified code is as follows:
Copy codeThe Code is as follows:
Class:
Def a (self ):
Pass
 
Class A1 ():
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 ())
Print ("dir class A1:", dir (A1 ))
A = A1 ()
Print ("dir object a (A1):", dir ())
Print ("dir function a. a:", dir (a. ))
Print ("dir current file:", curModuleDir)

4. 2. Method 2: import the current module
Reference the current module like other imports. The Code is as follows:
Copy codeThe Code is as follows:
# A. py
Import A as this # import current module
 
Class:
Def a (self ):
Pass
 
Class A1 ():
Def a1 (self ):
Pass

If _ name _ = '_ main __':
Print ("dir without arguments:", dir ())
Print ("dir class A:", dir ())
Print ("dir class A1:", dir (A1 ))
A = A1 ()
Print ("dir object a (A1):", dir ())
Print ("dir function a. a:", dir (a. ))
Print ("dir current file:", dir (this ))

4. 3. Method 3: Find the module based on the module name, and then call dir
We know that the module has an attribute _ name _ showing the module name. How can we find the module object based on the module name? You can use sys. modules. The Code is as follows:
Copy codeThe Code is as follows:
Import sys

Class:
Def a (self ):
Pass

Class A1 ():
Def a1 (self ):
Pass

If _ name _ = '_ main __':
Print ("dir without arguments:", dir ())
Print ("dir class A:", dir ())
Print ("dir class A1:", dir (A1 ))
A = A1 ()
Print ("dir object a (A1):", dir ())
Print ("dir function a. a:", dir (a. ))
Print ("dir current file:", dir (sys. modules [_ name _]) # Use _ name _ to obtain the current module object, and then use the object to get the dir