PYTHON__ Namespaces and Scopes

One: function nesting, in the process of calling a function, another call to other functions

def bar ():
    Print (' from Bar ')
def foo ():
    Print (' from foo ')
    Bar ()
Foo ()
The use of nested functions, broken down into the smallest operation, one call


Two: nested definition of function: Inside a function, a function is defined.

Def f1 ():
    x = 1
    def f2 ():
        Print (' from F2 ')
    F2 ()
F1 ()

The name space, where the name is stored, the exact name space is where the name and the value of the variable are bound
Built-in namespaces: Python's own name, generated when the Python interpreter starts, and contains some python built-in names
Global namespace: The name of the file-level definition at the time the file is executed
Local namespaces: During the execution of a file, if a function is called, the namespace of the function is generated, which is used to hold the name defined within the function, which takes effect when the function is called and expires after the call has ended.
Load order: Built-in namespace------> global Namespace-----> local namespace
Name Lookup Order: Local namespace------> global Namespace-----> built-in namespaces


Four: scope, range of effects
Global scope: Global survival, globally valid
Local scope: Local survival, locally valid

Def f1 ():
    x = 1
    y = 2
    Print (Locals ())
    Print (Globals ())
F1 ()
Print (Locals ())
Print (Globals ())
Print (Locals () is globals ())
Change the global name:

x = 1
Def f1 ():
    Global X
    x = 2
F1 ()
Print (x)

Change local name:

Def f1 ():
    x = 1
    def f2 ():
        x = 2
        Def f3 ():
            Nonlocal x# is the value directly above the function.
            x = 3
        F3 ()
    F2 ()
F1 ()


V: precedence, fixed at function definition, independent of call location

x = 1
Def f1 ():
    def f2 ():
        Print (x)
    return F2
Func = F1 ()
Func ()

PYTHON__ Namespaces and Scopes