Python built-in function locals

English documentation:

locals()

Update and return a dictionary representing the current local symbol table. Free variables are returned by locals() when it is called in function blocks, but not in class blocks.

Explanation :

　1. The function returns a dictionary consisting of local variables in the current scope and their values, similar to the globals function (returning global variables)

>>> locals()
{&#39;__package__&#39;: None, &#39;__loader__&#39;: <class &#39;_frozen_importlib.BuiltinImporter&#39;>, &#39;__doc__&#39;: None, &#39;__name__&#39;: &#39;__main__&#39;, &#39;__builtins__&#39;: <module &#39;builtins&#39; (built-in)>, &#39;__spec__&#39;: None}

>>> a = 1

>>> locals() # 多了一个key为a值为1的项
{&#39;__package__&#39;: None, &#39;__loader__&#39;: <class &#39;_frozen_importlib.BuiltinImporter&#39;>, &#39;a&#39;: 1, &#39;__doc__&#39;: None, &#39;__name__&#39;: &#39;__main__&#39;, &#39;__builtins__&#39;: <module &#39;builtins&#39; (built-in)>, &#39;__spec__&#39;: None}

　2. Can be used within functions.

>>> def f():
    print('before define a ')
    print(locals()) #作用域内无变量
    a = 1
    print('after define a')
    print(locals()) #作用域内有一个a变量，值为1

    
>>> f
<function f at 0x03D40588>
>>> f()
before define a 
{} 
after define a
{&#39;a&#39;: 1}

　3. The returned dictionary set cannot be modified.

>>> def f():
    print('before define a ')
    print(locals()) # 作用域内无变量
    a = 1
    print('after define a')
    print(locals()) # 作用域内有一个a变量，值为1
    b = locals()
    print('b["a"]: ',b['a']) 
    b['a'] = 2 # 修改b['a']值
    print('change locals value')
    print('b["a"]: ',b['a'])
    print('a is ',a) # a的值未变

    
>>> f()
before define a 
{}
after define a
{'a': 1}
b["a"]:  1
change locals value
b["a"]:  2
a is  1
>>>