为什么调用此方法会出现错误 "Unbound method ... instance as first arg"？

Question

class stack:
    def __init__(self):
        self.st = []
    def push(self, x):
        self.st.append(x)
        return self
    def pop(self):
        return self.st.pop()

有人能告诉我为什么我不能运行 python 并执行 stack.push(3) 而不会出现未绑定错误。我执行以下操作

>>> from balance import *
>>> stack.push(3)
Traceback (most recent call last):File "<stdin>", line 1, in <module>
TypeError: unbound method push() must be called with stack instance as first argument (got int instance instead)
>>>

但是当我写这段代码时，我可以毫无错误地压入堆栈：

import sys

k = sys.argv[1]

class stack:
    def __init__(self):
        self.st = []
    def push(self, x):
        self.st.append(x)
        return self
    def pop(self):
        return self.st.pop()
    def isEmpty(self):   #added an empty fucntion to stack class
        return self.st == []

def balance(k):
    braces = [ ('(',')'), ('[',']'), ('{','}') ] #list of braces to loop through
    st = stack() #stack variable

    for i in k:   #as it iterates through input 
              #it checks against the braces list
        for match in braces:
            if i == match[0]:  #if left brace put in stack
                st.push(i)
            elif i == match[1] and st.isEmpty():  #if right brace with no left
                st.push(i)                        #append for condition stateme$
            elif i == match[1] and not st.isEmpty() and st.pop() != match[0]:
                st.push(i)   #if there are items in stack pop
                         # for matches and push rest to stack

if st.isEmpty(): #if empty stack then there are even braces
    print("Yes")
if not st.isEmpty():  #if items in stack it is unbalanced
    print("No")


balance(k) #run balance function

Answer 1

错误告诉您确切的问题：

...method push() must be called with stack instance...

您正在这样做：

stack.push(3)

不是堆栈实例。您正在尝试将实例方法作为 class 方法调用，因为您尚未实例化 stack。例如：

>>> st = stack()
>>> st.push(3)

您实际上在平衡函数中正确地做到了这一点：

st = stack() #stack variable

现在您实际上拥有了 stack 的一个实例。您还 清楚地 在此处的代码中进一步正确使用它，例如：

st.push(i)

此外，你不应该调用 stack 一个变量，它是一个 class.

您还应该参考 PEP8 style guide 以遵守适当的约定。例如，classes 应该是大写的：stack 应该是 Stack

为什么调用此方法会出现错误 "Unbound method ... instance as first arg"？

Why is calling this method giving error "Unbound method ... instance as first arg"?

python

methods

class

instance

typeerror