PYTHON函数

• 函数是指组织好的，可重复使用的，用来实现特定功能的代码段

• 语法:

  ​ def 函数名 (传入参数):

  ​ 函数体

  ​ return 返回值

• 参数可以省略，返回值可以省略(省略时接受到None，也可以手动写return None)

• None作为特殊的字面量，用于表示: 空、无意义;在if判断中None等同于False

# 例
def str_len(data):
    for x in data:
        print(x,end=" ")

a = "ABCDEF"
str_len(a)

• global关键字: 声明函数中的变量是全局变量;用于在函数内部修改全局变量的值

# ATM

money = 10000.00
name = "XIANG"

def main_menu():
    print()
    print("WELCOME TO ATM")
    print("SEARCH MONEY [INPUT 1]")
    print("SAVE MONEY INPUT 2]")
    print("TAKE MONEY [INPUT 3]")
    print("LEAVE [INPUT OTHER CHARACTER]")
    input_data = input("PLEASE INPUT:")
    if input_data == "1":
        search_money()
    elif input_data == "2":
        save_money()
    elif input_data == "3":
        take_money()
    return None

def search_money():
    print()
    print("-----------SEARCH MONEY-----------")
    print(name+" SIR,YOUR MONEY :"+str(money))
    input("INPUT ANY CHARACTER TO MAIN MENU:")
    main_menu()

def save_money():
    print()
    print("-----------SAVE MONEY-----------")
    save_money = float(input("INPUT YOUR SAVE AMOUNT:"))
    global money
    money += save_money
    print("SUCCESSFUL!NOW YOUR MONEY:"+str(money))
    input("INPUT ANY CHARACTER TO MAIN MENU:")
    main_menu()

def take_money():
    print()
    print("-----------TAKE MONEY-----------")
    save_money = float(input("INPUT YOUR TAKE AMOUNT:"))
    global money
    money -= save_money
    print("SUCCESSFUL!NOW YOUR MONEY:" + str(money))
    input("INPUT ANY CHARACTER TO MAIN MENU:")
    main_menu()

main_menu()