# 基本while循環
count = 0
while count < 5:
    print(count)
    count += 1  # 別忘了更新條件

# 使用break退出循環
number = 0
while True:
    if number >= 5:
        break
    print(number)
    number += 1

注意事項：

• 必須在循環內更新條件，否則可能造成無限循環
• 確保循環條件最終會變為False
• 可以使用break強制退出循環

import random
target = random.randint(1, 100)
guess_count = 0

while True:
    guess = int(input("猜一個1-100的數字："))
    guess_count += 1
    
    if guess == target:
        print(f"恭喜猜對了！共猜了{guess_count}次")
        break
    elif guess < target:
        print("太小了，再試試")
    else:
        print("太大了，再試試")

correct_password = "python123"
max_attempts = 3
attempts = 0

while attempts < max_attempts:
    password = input("請輸入密碼：")
    if password == correct_password:
        print("登入成功！")
        break
    attempts += 1
    remaining = max_attempts - attempts
    print(f"密碼錯誤，還有{remaining}次機會")

# 當while循環正常結束時執行else
count = 0
while count < 3:
    print(count)
    count += 1
else:
    print("循環正常結束")

# break會跳過else
count = 0
while count < 3:
    if count == 2:
        break
    print(count)
    count += 1
else:
    print("這句不會執行")

無限循環

# 錯誤示例
while count < 5:
    print(count)
    # 忘記更新count

# 正確示例
while count < 5:
    print(count)
    count += 1

輸入驗證

# 確保輸入有效數字
while True:
    try:
        age = int(input("請輸入年齡："))
        if 0 <= age <= 120:
            break
        print("請輸入有效年齡（0-120）")
    except ValueError:
        print("請輸入數字")