Case Conversion Python

Following Code Will Convert The Case of Entered String 
i.e lower to UPPER and UPPER to lower



Code::

def conversion(l):
    li=list(l)
    for i in range(0,len(l)):
        if 'a'<=li[i]<='z': li[i]=chr(ord(li[i])-32)
        elif 'A'<=li[i]<='Z': li[i]=chr(ord(li[i])+32)
    stri=''
    return stri.join(li)

s=input("Enter String: ")
print(conversion(s))


Output::