Python基础：if与while语句详解及实战应用

names=['xiaozhan','caiyilin','zhoushen','DAOlang','huangxiaoming']
for name in names:
    if name == 'caiyilin':   #注意：双等号'=='解读为“变量name的值是否为'caiyilin' 
        print(name.upper())
    else:
        print(name.title())

my_fav_name = 'daolang'
for name in names:
    if name == my_fav_name:
        print('Yes')
    print('No')    
print('\n')
  
for name in names:
    if name.lower() == my_fav_name:
        print('Yes')
    print('No')       
print('\n')
#下方使用  if……else语句  
for name in names:
    if name.lower() != my_fav_name:   #检查是否不相等
        print('NO')
    else:
        print('YES') 

ages=['73','12','60','1','10','55','13']
for age in ages:
    if   age > str(60):  #注意：ages中为列表字符串，所以age也是字符串，无法与整型的数字相比，需要先将数字转化为字符串再比较。
        print("The "+str(age)+" years has retired!")
    elif age > str(18) and age<=str(60):    #两个条件都为True时
        print("The "+str(age)+" years is an Adult!")
    elif age > str(12):
        print("The "+str(age)+" years is a student!")
    else:
        print("The "+str(age)+" years is a child!")

current_number = 1
while current_number <= 5:
    print(current_number)
    current_number += 1
print("\n")
print(current_number)

prompt = "\nTell me your secret, and I will repeat it back to you:"
prompt += "\nEnter 'quit' to end the program. "

active = True  #定义一个标志
while active:  #当active为真的时候，执行程序，
    message = input(prompt) 
    if message == 'quit': #当输入信息为quit时，标志active为False，程序停止
        active = False
    else:
        print(message)

prompt = "\nPlease enter the name of a city you have visited:"
prompt += "\n(Enter 'quit' when you are finished.) "

while True:
    city = input(prompt)
    if city == 'quit':
        break
    else:
        print("I'd love to go to " + city.title() + "!")

current_number = 0
while current_number < 10:
    current_number += 1  #以1逐步增加
    if current_number % 2 == 0: #求模运行，是2的倍数，为0
        continue  #忽略并继续运行。
    print(current_number) #打印出数字

unconfirmed_users = ['Lucy', 'Bush', 'lincon', 'lucy',
                     'jack', 'lily', 'lucy', 'hanmeimei']  # 首先，创建一个待验证用户列表
confirmed_users = []  # 创建一个用于存储已验证用户的空列表

while unconfirmed_users:  # 验证每个用户，直到没有未验证用户为止
    current_user = unconfirmed_users.pop()  # 注意pop()是从最后一个开始。
    print("Verifying user: " + current_user.title())  # 打印验证的用户，且首字母大写
    confirmed_users.append(current_user)  # 将每个经过验证的列表都移到已验证用户列表中，
    # 相当于将unconfirmed_users倒序保存到current_user中
print("\nThe following users have been confirmed:")  # 显示所有已验证的用户
for confirmed_user in confirmed_users:  # for循环打印每个已验证的用户名
    print(confirmed_user.title())
print("\n")
# 删除包含特定的所有列表元素
while 'lucy' in confirmed_users:  # while 循环，因为lucy在列表中至少出现了一次
    confirmed_users.remove('lucy')  # 删除除最后一个外的其他相同的元素
print(confirmed_users)

responses = {}#定义一个空字典
polling_active = True # 设置一个标志，指出调查是否继续
while polling_active:
    name = input("\nWhat is your name? ")  # 提示输入被调查者的名字和回答
    response = input("Which mountain would you like to climb someday? ")
    responses[name] = response # 将答卷存储在字典中，即name是key,变量response 是值
    repeat = input("Would you like to let another person respond? (yes/ no) ")# 看看是否还有人要参与调查
    if repeat == 'no':  #如无人参与调查，将标志设置为False,退出运行。
        polling_active = False
# 调查结束，显示结果
print("\n--- Poll Results ---")
print(responses)  #把字典打印出来  
for name, response in responses.items():  #访问字典
    print(name.title() + " would like to climb " + response + ".")