python3學習筆記8--用戶輸入和while循環

• 函數 input() 的工作原理

函數input() 讓程序暫停運行，等待用戶輸入一些文本。獲取用戶輸入後，Python將其存儲在一個變量中，以方便你使用。

函數input() 接收一個參數，即要向用戶顯示的提示或說明，讓用戶如何操作。

1、編寫清晰的程序

name = input("please enter you name: ")
print("Hello," + name + "!")

2、使用int() 來獲取數值輸入

height = input("How tall are you ,in inchaes ? ")
height = int(height)

if height >= 36:
    print("\n You're tall enough to ride! ")
else:
    print("\n You'll be able to ride when you're a litter older.")

3、求模運算符

求模運算符 （%）是一個很有用的工具，它將兩個數相除並返回餘數：

number = input("Enter a number, and I'll tell you if it's even or odd: ")
number = int(number)

if number % 2 ==0:
    print("\nThe number " + str(number) + " is even.")
else:
    print("\nThe number " + str(number) + " is odd.")

• while 循環簡介

for 循環用於針對集合中的每個元素都一個代碼塊，而while 循環不斷地運行，直到指定的條件不滿足爲止。

1、使用while循環

current_number = 1
while current_number <=5:
    print(current_number)
    current_number +=1

2、讓用戶選擇何時退出

prompt = "\nTell me something, and I will repeat it back to you:"
prompt += "\nEnter 'quit' to end the program. "
message = ""
while message != 'quit':
    message = input(prompt) 
    print(message)

3、使用標誌

定義一個變量，用於判斷整個程序是否處於活動狀態。這個變量被稱爲標誌。

prompt = "\nTell me something, and I will repeat it back to you:"
prompt += "\nEnter 'quit' to end the program. "
message = ""
while message != 'quit':
    message = input(prompt)
    if message == 'quit':
        active = False
    else:
        print(message)

4、使用break 退出循環

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() + "!")

5、在循環中使用continue

current_number = 0
while current_number <=5:

    current_number +=1
    if current_number % 2 ==0:
        continue
    print(current_number)

6、避免無限循環

• 使用while 循環來處理列表和字典

1、在列表中移動元素

# 首先，創建一個待驗證用戶列表
# 和一個用於存儲已驗證用戶的空列表
unconfirmed_users = ['alice', 'brian', 'candace']
confirmed_users = []
# 驗證每個用戶，直到沒有未驗證用戶爲止
# 將每個經過驗證的列表都移到已驗證用戶列表中
while unconfirmed_users: 
    current_user = unconfirmed_users.pop()
    print("Verifying user: " + current_user.title())
    confirmed_users.append(current_user)
# 顯示所有已驗證的用戶
print("\nThe following users have been confirmed:")
for confirmed_user in confirmed_users:
    print(confirmed_user.title())

2、刪除包含特定值的所有列表元素

pets = ['dog', 'cat', 'dog', 'goldfish', 'cat', 'rabbit', 'cat']
print(pets)
while 'cat' in pets:
    pets.remove('cat') 
print(pets)

3、使用用戶輸入來填充字典

responses = {}
# 設置一個標誌，指出調查是否繼續
polling_active = True
while polling_active:
    # 提示輸入被調查者的名字和回答
    name = input("\nWhat is your name? ")
    response = input("Which mountain would you like to climb someday? ")
    # 將答卷存儲在字典中
    responses[name] = response
    # 看看是否還有人要參與調查
    repeat = input("Would you like to let another person respond? (yes/ no) ")
    if repeat == 'no':
        polling_active = False
# 調查結束，顯示結果
print("\n--- Poll Results ---")
for name, response in responses.items():
    print(name + " would like to climb " + response + ".")