Python判断是否为小数

def is_float(s):
    s = str(s)
    if s.count('.') == 1:
        left,right = s.split('.') #[1,1]#-s.2
        if left.isdigit() and right.isdigit():
            return True
        elif left.startswith('-') and left.count('-')==1 \
                and left[1:].isdigit() and right.isdigit():
            return True

    return False