python中 报错xxx takes 1 positional argument but 2 were given问题解决

python中的类默认第一个形参delf必传，调用时传入的实参数对应的是delf后面的形参：

class Cat:
    ## 属性

    ## 方法
    def eat(delf, val):
        print('---The cat is eating ' + str(val))
    ## 第一个参数delf必传
    def dring(delf, drinking):
        print('---The cat is drinking ' + str(drinking))

smcat = Cat()
## food对应val,milk对应drinking
smcat.eat('food')
smcat.dring('milk')