function scopes in Python

This article mainly introduces the function scope of Python, has a certain reference value, now share to everyone, the need for friends can refer to

In Python, a function is a scope. This article focuses on the functional scope of Python, interested friends to see it together

In Python, a function is a scope

name = ' Xiaoyafei ' def change_name ():  name = ' Showa '  print (' name in Change_name: ', name) Change_name () # Call function print ( "Outside the name:", name)

The results of the operation are as follows:

Name in Change_name: Showa
On the outside of the Name:xiaoyafei

Let's try again how is it found in nested functions?

Age = 15def func ():  print (' First Age: ', age) # First layer age:15  def func2 (): Age    =    Func2 print ("Age in", age) # Fu age:73    def func3 () in Nc2 (): Age      = all      print ("Age in Func3:", age) # func3 in age:84 func3    () # Call func3 function  Func2 () # Call Func2 function func ()

In the above nested function, it is well explained that a function is a scope, then we can now change the code a little bit to see the situation?

Age = 15def func ():  print (' First layer Age: ', age) # First layer age:15  def func2 ():    print ("Age in Func2:", age) # Func2 in age:15 # See, if there is no age variable in the current scope, then it will look up    def func3 (): Age      =      print ("Age in Func3:", age) # func3 in age:84    func3 () # Call the FUNC3 function  Func2 () # Call the Func2 function func ()

Well, then, when someone says, "a whole bunch of crap is about local variables and global variables, then I want to ask: in this nested function, there is no age variable in Func2, so how does it find the global variable, age = 15?"

Now we need to look at the scope lookup order:

Variable Scope LEGB

• namespaces within the L:locals function, including local variables and arguments

• E:enclosing the namespace of the outer nested function, that is, adjacent to the previous layer, for example, said: FUNC2 No age variable will go to the Func find this

• G:globals Global Variables

• B:builtins the namespace of the built-in module

Cough, or first understand what is the name space?

namespace, aka name space, as the name implies is the place to store names, what name? for example, x = 1, 1 is stored in memory, so where is the variable name x stored? Namespaces are places where names X and 1 bind.

>>> x = 1>>> ID (1) 1576430608

The namespace is divided into the following 3 types:

• Locals: is a namespace within a function, including local variables and formal parameters

• GLOBALS: global variable, the namespace of the module in which the function is defined

• Builtins: Namespaces for built-in modules

Different scopes of variables are determined by the namespace in which the variable resides.

Scope is range

• Global scope: Global survival, globally valid

• Local scope: Temporary inventory, partially valid

Let's take an example to see

Level = ' L0 ' n = 22def func (): Level  = ' L1 '  n = "  print (Locals ()) # {' n ': ' ' Level ': ' L1 '} said in Python, a letter The number is a scope, which perfectly embodies the  def outer ():    n = level    = ' L2 '    print (locals (), N) # {' Level ': ' L2 ', ' n ': +}    EF inner (): Level      = ' L3 '      print (locals (), N) # {' Level ': ' L3 ', ' n ': "Inner}" () ()  outer () func ()

With the rules of L-E-G-->b, that is: in the local can not find, will go to local outside the local search (such as closures), and can not find the global find, and then go to the built-in function to find.