练习3

a = 0
while True:
    n = a + 1
    for i in range(4):
        n = n * 5 + 1
        if n % 4 == 0:
            n = n / 4
        else:
            a += 1
            break
    else:
        print(int(n * 5 + 1))
        break

练习4

a = 1
b = 1
for i in range(50):
    print(a,end=" ")
    c = a+b
    a = b
    b = c

练习5

n = input("请输入一个整数：")
if n==n[::-1]:
    print(n,"是回文数")
else:
    print(n,"不是回文数")

练习6和练习4是一样的

练习7

def calc(a,op,b):
    if op=="+":
        return a+b
    if op=="-":
        return a-b
    if op=="*":
        return a*b
    if op=="/":
        return a/b
    else:
        return None

a = int(input("请输入一个整数："))
op = input("请输入 +-*/：")
b = int(input("请输入另一个整数："))
print("结果：",calc(a,op,b))

练习8

s = []
for i in range(4):
    s.append(input())
for i in range(4):
    print(s[i][0],end="")

如有帮助，望采纳！谢谢!