Python3-笔记-C-006-函数-定义与全局变量

# === 函数 ===
def function1(): # 无参函数
    print("×参数 ×返回") # 无返回

def function2(arg1, arg2): # 带参函数(位置参数)
    return "√参数 √返回" # 有返回

def function2_1(arg1, arg2):
    return arg1, arg2 # 元组形式返回多个值

def function3(*args): # 不定长参数(位置参数),把位置参数(*args)转成元组
    print("function3: ", args)

def function3_1(**kwargs): # 不定长参数(关键字参数), 把关键字参数(**kwargs)转成字典
    print("function3_1: ", kwargs)

def function4(arg1 = 5): # 缺省参数(不传参将使用默认值)(注意:Python不支持函数重载,该方式解决了重载问题)
    print("function4:%s" % arg1)

def function5(n): #递归示例
    "打印100以内的奇数"
    if n <= 100:
        print(n)
        n += 2
        return function5(n)


# === 位置参数 和 关键字参数 的混合使用 ===
def function6(arg, *args):
    print("function6: ", arg)
    print("function6: ", args)

def function7(arg, age=21, **kwargs):
    print("function7: ", arg)
    print("function7: ", age)
    print("function7: ", kwargs)

def function8(arg, age=21, *args, **kwargs): # 位置参数 只能写在 关键字参数 前面
    print("function8: ", arg)
    print("function8: ", age)
    print("function8: ", args)
    print("function8: ", kwargs)


function1() # ×参数 ×返回
print(function2("a", "b")) # √参数 √返回
print(function2_1("a", "b")) # ('a', 'b')

function3(1, 2, 3) # function3:  (1, 2, 3)
function3(*[1, 2, 3]) # function3:  (1, 2, 3)
function3_1(a="A", b="B", c="C") # function3_1:  {'a': 'A', 'b': 'B', 'c': 'C'}
function3_1(**{"a":"A", "b":"B", "c":"C"}) # function3_1:  {'a': 'A', 'b': 'B', 'c': 'C'}
function4(3) # function4:3
function5(50)
function6(1, 2, 3, 4, 5)
    # function6:  1
    # function6:  (2, 3, 4, 5)
function6(1, *[2, 3, 4, 5])
    # function6:  1
    # function6:  (2, 3, 4, 5)
function7(1, num=12, age=50)
    # function7:  1
    # function7:  50
    # function7:  {'num': 12}
function8(1, 22, 2, 3, num=12)
    # function8:  1
    # function8:  22
    # function8:  (2, 3)
    # function8:  {'num': 12}

# === 变量 ===
global_var = 123 # 全局变量,作用域整个程序
global_var_c = 321
def localvariable():
    local_var = 456 # 局部变量, 作用域在子程序
    global_var_c = 123 # 子程序不能修改全局变量(引用(如:list,class)除外)
    print("global_var: {}; global_var_c: {}; local_var: {}".format(global_var, global_var_c, local_var)) # => 123, 123, 456

localvariable()
print("global_var: {}; global_var_c: {}".format(global_var, global_var_c)) # => 123, 321


# === 修改全局变量 ===
global_list = {"num" : 123}
def localvariable_cg():
    global_list["num"] = 321
    print("global_list: {}".format(global_list)) # => {'num': 321}

localvariable_cg()
print("global_list: {}".format(global_list)) # => {'num': 321}


# === 修改全局变量的作死写法 (不建议使用这种写法, 容易造成全局变量使用混乱) ===
global_err = 123
def localvariable_err():
    global global_err
    global_err = 321
    print("global_err: {}".format(global_err)) # => 321

localvariable_err()
print("global_err: {}".format(global_err)) # => 321