判断语句

a = int(input())
b = 5

if a >= b:
    print("%d is >= 5" % a)
    print("a is so big")
else:
    print("%d is < 5" % a)
    print("a is so small")

输出 a 的绝对值

if a >= 0:
    print(a)
else:
    print(-a)

找a,b,c的最大值

a,b,c = map(int,input().split())
if a > b:
    if a > c:
        print(a)
    else:
        print(c)
else:
    if b > c:
        print(b)
    else:
        print(c)

else if要写成 elif

a = int(input())
if a >= 80:
    print("A")
elif a >= 70:
    print("B")
elif a >= 60:
    print("C")
else:
    print("D")

pass空语句

# 如果a>=80就不执行任何动作,否则输出a
a = int(input())
if a >= 80:
    pass
else:
    print(a)

逻辑条件表达式

# and:并且 , or:或者 , not:非
# 优先级：not > and > or
# 判断闰年
year = int(input())
if year % 100 != 0 and year % 4 == 0 or year % 400 == 0:
    print("yes")
else:
    print("no")