先上程序！！！！

切片并连接字符or字符串循环左移

s=str(raw_input('Please input the string:'))
n=int(input('Please input the non-negative integer:'))
front=s[0:n:1]
tail=s[n: :1]
new_s=''.join([tail,front])
print(new_s)

嘻嘻，简单第一步，再接再厉~