How can I find whether element exist?

How can I find whether element exist before using for attribute or if element has label

def getidByLabel(self,driver,target_type,target_label,row_position):
    if target_type == 'form':
        attr_id = driver.find_element_by_xpath("//label[text()='" + target_label + "']").get_attribute("for")
        return attr_id
    elif target_type == 'table':
        attr_id = driver.find_elements_by_xpath("//label[text()='" + target_label + "']").__getitem__(row_position).get_attribute("for")
        return attr_id