python判断一个四位整数是否是回文素数，闰年，大写字母转小写字母，解方程

from math import sqrt
def sushu(x):
    if(x==2):
        return True
    else:
        for i in range(2,x):
            if(x%i==0):
                return False
        return True
def huiwen(n):
    a = n // 1000
    b = (n // 100) % 10
    c = (n // 10) % 10
    d = n % 10
    m = a + b * 10 + c * 100 + d * 1000
    if(m==n):
        return True
    else:
        return False
for i in range(1000,10000):
    if huiwen(i) and sushu(i):
        print(i)

def run(n):
    if(n%4==0)and(n%100!=0) or(n%400==0):
        print(n,"年是闰年")
run(1600)

def zimu():
    a=input("请输入一个需要转化的字母")
    c=a if((a>='a') and (a<='z')) else (chr(ord(a)+32))
    print(c)
zimu()

from math import sqrt
def jiefangcheng():
    a=int(input("a="))
    b = int(input("b="))
    c= int(input("c="))
    d=b**2-4*a*c
    if(d>=0):
        x1=(-b+sqrt(d))/2*a
        x2=(-b-sqrt(d))/2*a
        print(x1,x2)
    else:
       e=sqrt(-d)/2*a
       f=-b/2*a
       print(complex(f,e),complex(f,-e))
jiefangcheng()