保存和显示Python计算器的计算历史记录

Question

我需要扩展给定的计算程序以记录计算，并使用附加命令'？

要做的事情：

1. 声明列表以存储以前的操作，
2. 将操作员，操作数和结果保存为单个字符串，每个操作后，每个操作都在每个计算后
3. 实现一个历史记录（）函数来处理操作'？'
4. 使用新命令“？”显示完整保存的操作列表（按执行顺序）显示
5. 如果历史记录时没有以前的计算？使用命令，您可以显示以下消息“没有过去的计算”

有人可以帮助我吗？

  return a+b
  
def subtract(a,b):
  return a-b
  
def multiply (a,b):
  return a*b

def divide(a,b):
  try:
    return a/b
  except Exception as e:
    print(e)
def power(a,b):
  return a**b
  
def remainder(a,b):
  return a%b
  
def select_op(choice):
  if (choice == '#'):
    return -1
  elif (choice == '$'):
    return 0
  elif (choice in ('+','-','*','/','^','%')):
    while (True):
      num1s = str(input("Enter first number: "))
      print(num1s)
      if num1s.endswith('$'):
        return 0
      if num1s.endswith('#'):
        return -1
        
      try:
        num1 = float(num1s)
        break
      except:
        print("Not a valid number,please enter again")
        continue
    
    while (True):
      num2s = str(input("Enter second number: "))
      print(num2s)
      if num2s.endswith('$'):
        return 0
      if num2s.endswith('#'):
        return -1
      try:  
        num2 = float(num2s)
        break
      except:
        print("Not a valid number,please enter again")
        continue
    

    if choice == '+':
      result = add(num1, num2)
    elif choice == '-':
      result = subtract(num1, num2)
    elif choice == '*':
      result = multiply(num1, num2)
    elif choice == '/':
      result =  divide(num1, num2)
    elif choice == '^':
      result = power(num1, num2)
    elif choice == '%':
      result = remainder(num1, num2)
    else:
      print("Something Went Wrong")
      
    
  else:
    print("Unrecognized operation")
    
while True:
  print("Select operation.")
  print("1.Add      : + ")
  print("2.Subtract : - ")
  print("3.Multiply : * ")
  print("4.Divide   : / ")
  print("5.Power    : ^ ")
  print("6.Remainder: % ")
  print("7.Terminate: # ")
  print("8.Reset    : $ ")
  print("8.History  : ? ")
  
  # take input from the user
  choice = input("Enter choice(+,-,*,/,^,%,#,$,?): ")
  print(choice)
  if(select_op(choice) == -1):
    #program ends here
    print("Done. Terminating")
    exit()```

Answer 1

您需要声明函数历史记录（）和列表，

last_calculation = []

def history():
  global last_calculation
  if last_calculation == []:
    print("No past calculations to show")
  else:
    for i in last_calculation:
        print(*i)  #for single line

然后在if循环中添加以下代码到操作的末尾，

last_calculation.append(result)

然后触发histort（）函数，使用“继续”以在呼叫历史记录之后进行操作（）

if choice=='?':
    history()
    continue

Answer 2

为了保存历史记录，您可以添加一个全列表的全局变量。这样：

history = []

...

def record_history(*args):
    history.append(args)


def select_op(choice):
    ...    
    record_history(choice, num1, num2, result)
    ...

这不是不是最干净的解决方案，而是最简单的解决方案，因为您仅使用功能。理想情况下，功能不应具有任何副作用，不应取决于程序的“状态”。为了保存任何类型的“状态”将此实现重构为类，将使事情变得更加干净。 诸如

class Calculator:

    def __init__(self):
        self.history = []

    def record_history(self, *args):
        self.history.append(args)

    def select_op(self, choice):
        ...
        self.record_history(choice, num1, num2, result)
        ...

提示

通过使用标准库使您的生活更简单

1. 操作员库提供了add，sub， mul等。
2. cmd.cmd类可用于轻松构建交互式控制台。

Answer 3

这是我对您面临的问题的回答。我创建了这个并检查了它。

calculations = []

def record_history(args):
    calculations.append(args)

def history():
    if calculations == []:
        print("No past calculations to show")
    else:
        for i in calculations:
            print(i)

def add(a,b):
    return a+b

def subtract(a,b):
    return a-b

def multiply (a,b):
    return a*b

def divide(a,b):
    try:
        return a/b
    except Exception as e:
        print(e)

def power(a,b):
    return a**b

def remainder(a,b):
    return a%b

def select_op(choice):
    if choice == '#':
        return -1
    elif choice == '
:
        return 0
    elif choice in ('+', '-', '*', '/', '^', '%'):
        while True:
            num1s = input("Enter first number: ")
            print(num1s)
            if num1s.endswith('
):
                return 0
            if num1s.endswith('#'):
                return -1

        try:
            num1 = float(num1s)
            break
        except:
            print("Not a valid number, please enter again")
            continue

        while True:
            num2s = input("Enter second number: ")
            print(num2s)
            if num2s.endswith('
):
                return 0
            if num2s.endswith('#'):
                return -1
            try:  
                num2 = float(num2s)
                break
            except:
                print("Not a valid number, please enter again")
                continue

        result = 0.0
        last_calculation = ""

        if choice == '+':
            result = add(num1, num2)
        elif choice == '-':
            result = subtract(num1, num2)
        elif choice == '*':
            result = multiply(num1, num2)
        elif choice == '/':
            result =  divide(num1, num2)
        elif choice == '^':
            result = power(num1, num2)
        elif choice == '%':
            result = remainder(num1, num2)
        else:
            print("Something Went Wrong")

        last_calculation =  "{0} {1} {2} = {3}".format(num1, choice, num2, result) 
        print(last_calculation)
        record_history(last_calculation)

    elif choice == '?':
        history() 

    else:
        print("Unrecognized operation")

while True:
    print("Select operation.")
    print("1.Add      : + ")
    print("2.Subtract : - ")
    print("3.Multiply : * ")
    print("4.Divide   : / ")
    print("5.Power    : ^ ")
    print("6.Remainder: % ")
    print("7.Terminate: # ")
    print("8.Reset    : $ ")
    print("8.History  : ? ")

    # take input from the user
    choice = input("Enter choice(+,-,*,/,^,%,#,$,?): ")
    print(choice)
    if select_op(choice) == -1:
        #program ends here
        print("Done. Terminating")
        break