python学习-24 局部变量与全局变量

局部变量与全局变量

1.没有缩进的变量，为全局变量

name = 'jphn'

在子程序里定义的变量，局部变量

2.

name = 'jphn'                    #全局变量

def a():
    name='andy'                    #局部变量
    print('a',name)
a()

运行结果：

a andy

Process finished with exit code 0

3.global 可以修改全局变量

不修改之前：

name = 'jphn'

def a():
    name='andy'
    print('a',name)
a()

print(name)

运行结果：

a andy
jphn

Process finished with exit code 0

想要修改全局变量;

name = 'jphn'

def a():
    global name           #nonlocal 指定上一级变量， global指定全局变量
    name='andy'
    print('a',name)
a()

print(name)

运行结果：

a andy
andy

Process finished with exit code 0

4.嵌套

name = '小明'                            

def a():
    name = '小红'
    print(name)
    def b():
        name = '小刚'
        print(name)
        def c():
            name = '小王'
            print(name)
        print(name)
        c()
    b()
    print(name)
a()

运行结果：

小红
小刚
小刚
小王
小红

Process finished with exit code 0

5.前向引用

函数即变量

第一：

def bar():
    print('from bar')
def foo():
    print('from foo')
    bar()
foo()

运行结果：

from foo
from bar

Process finished with exit code 0

第二：

def foo():
    print('from foo')
    bar()
def bar():
    print('from bar')
foo()

运行结果：

from foo
from bar

Process finished with exit code 0