CS50P: 1. Conditionals

运算符

python中有 >= 和 <= ，其余和C一样

python支持 90 <= score <= 100

布尔运算

True or False

选择语句

if

if x < y:
    print("x is less than y")
if x > y:
    print("x is greater than y")
if x == y:
    print("x is equal to y")

• :
• .... 四个缩进，表示只有当 if 为真，该语句才能被执行。有缩进是一个代码块

代码的逻辑：三个 if 都会被执行

elif

if x < y:
    print("x is less than y")
elif x > y:
    print("x is greater than y")
elif x == y:
    print("x is equal to y")

else

if x < y:
    print("x is less than y")
elif x > y:
    print("x is greater than y")
else:
    print("x is equal to y")

match

类似 switch

原：

if name == "Harry" or name == "Hermione" or name == "Ron":		#字符串 ==
    print("Gryffindor")
elif name == "Draco":
    print("Slytherin")
else:
    print("Who?")

match：

match name:
    case "Harry" | "Hermione" | "Ron": 
        print("Gryffindor")
    case "Draco":
        print("Slytherin")
    case _:
        print("Who?")

• case _: 表示else
• | 在case中表示或

Pythonic Expressions

def is_even(x):
    return True if x % 2 == 0 else False

def is_even(x):
    return x % 2 == 0