Python if 语句

1. 使用 and 检查多个条件

age_0 = 22
age_1 = 28

if age_0 >= 21 and age_1 >= 21:
    print("age_0 >= 21 and age_1 >= 21")
else:
    print("age_0 < 21 or age_1 < 21")

2. 使用 or 检查多个条件

age_0 = 22
age_1 = 18

if age_0 >= 21 or age_1 >= 21:
    print("age_0 >= 21 or age_1 >= 21")
else:
    print("age_0 < 21 and age_1 < 21")

3. 检查特定值是否包含在列表中

requested_toppings = ['mushrooms', 'onions', 'pineapple']
if 'mushrooms' in requested_toppings:
    print("'mushrooms' in requested_toppings")
else:
    print("'mushrooms' not in requested_toppings")

4. 检查特定值是否不包含在列表中

requested_toppings = ['mushrooms', 'onions', 'pineapple']
if 'mushroom' not in requested_toppings:
    print("'mushroom' not in requested_toppings")
else:
    print("'mushroom' in requested_toppings")

5. 确定列表不是空的

requested_toppings = ['mushrooms', 'onions', 'pineapple']

if requested_toppings:  # 判断列表是否为空
    if 'mushrooms' in requested_toppings:
        print("'mushrooms' in requested_toppings")
    else:
        print("'mushrooms' not in requested_toppings")

本文参考自 《Python 编程：从入门到实践》