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我道歉评估中缀表示法，如果我似乎愚蠢这里，但我难倒...因为我说需要有这样的程序，使用堆栈计算中间符号表情，但我不能为我的生命得到这件事情适当地解决。使用Python堆栈问题
如果有人可以帮助我解决我的代码，并可能解释，我出了错那么我将非常感激。此外，比较遗憾的是靠不住的格式，这是我的第一篇文章，我不完全理解的代码输入格式。
import operator
def Main():
#In main, necessary stacks are generated and
#all calculations and methods are called and preformed.
opStack = ArrayStack()
numStack = ArrayStack()
opList = ['*', '/', '+', '-']
nums = '1234567890'
parn = ['(', ')']
toEval = input('Enter the Expression: ')
toEval = toEval.split()
#print(toEval)
for each in toEval:
if each in nums:
numStack.push(each)
if each == parn[0]:
opStack.push(each)
if each in opList:
if each == opList[2] or opList[3]:
opStack.push(each)
if each == opList[0] or opList[1]:
while opStack.top() == (opList[2] or opList[3]) and len(opStack) > 0 and len(numStack) >= 2:
ans = Eval(numStack.pop(),numStack.pop(),opStack.pop())
numStack.push(ans)
opStack.push(each)
if each == parn[1]:
while opStack.top() != "(":
ans = Eval(numStack.pop(),numStack.pop(),opStack.pop()) # this line is poping the empty stack
numStack.push(ans)
opStack.pop()
while opStack.is_empty() != True:
ans = Eval(numStack.pop(),numStack.pop(),opStack.pop())
numStack.push(ans)
print(ans)
def Eval(num1, num2, op):
#two numbers and an op are pulled from stacks, op checked against dict
#dict should supply necessary
ops2 = {"+": operator.add, "-": operator.sub, "*": operator.mul, "/": operator.truediv}
op_char = op
op_func = ops2[op_char]
res = op_func(float(num1), float(num2))
return res
class ArrayStack:
# LIFO Stack implementation using a Python list as underlying storage.
def __init__(self):
# Create an empty stack.
self._data = [] # nonpublic list instance
def __len__(self):
# Return the number of elements in the stack.
return len(self._data)
def is_empty(self):
# Return True if the stack is empty.
return len(self._data) == 0
def push(self, e):
# Add element e to the top of the stack.
self._data.append(e) # new item stored at end of list
def top(self):
# Return (but do not remove) the element at the top of the stack.
# Raise Empty exception if the stack is empty.
if self.is_empty():
raise Empty('Stack is empty')
return self._data[-1] # the last item in the list
def pop(self):
#Remove and return the element from the top of the stack (i.e., LIFO).
#Raise Empty exception if the stack is empty.
if self.is_empty():
raise Empty('Stack is empty')
return self._data.pop() # remove last item from list
Main()