animals = ['cow', 'duck', 'cat', 'dog']
animals.reverse()
print(animals)



word = " 窗前明月光，疑是地上霜。 "
print(word.strip())



count=0
while count < 50:
    count+=1
    if count % 2 == 0:
        continue
    print(count,end=",")


import turtle
for i in range(4):
    turtle.seth((i+1)*90)
    turtle.circle(50,90)#每次运动完都指向x正半轴方向
    turtle.seth(-90+i*90)
    turtle.circle(50,90)
turtle.hideturtle




import math
try:
    a = eval(input('请输入底数：'))
    b = eval(input('请输入真数：'))
    c = math.log(b,a)
except ValueError:
    if a<=0 and b>0:
        print("底数不能小于等于0")
    elif b<=0 and a>0:
        print("真数不能小于等于0")
    elif a<=0 and b<=0:
        print("真数和底数都不能小于等于0")
except ZeroDivisionError:
    print('底数不能为1')
except NameError:
    print('输入必须为实数')
else:
    print(c)



intxt = input("请输入明文：")
for p in intxt:
    if "a"<=p<="z":
        print(chr(ord("a")+(ord(p)-ord("a")+3)%26),end=" ")
    elif "A"<=p<="Z":
        print(chr(ord("A")+(ord(p)-ord("A")+3)%26),end=" ")
    else:
        print(p,end="")