保存并显示python计算器的计算历史

Question

I need to extend the given calculator program to record the calculations, and recall them as a list using an additional command '?'.

Things to do:

1. Declare a list to store the previous operations
2. Save the operator, operands, and the results as a single string, for each operation after each calculation
3. implement a history() function to handle the operation '?'
4. Display the complete saved list of operations (in the order of execution) using a new command '?'
5. If there are no previous calculations when the history '?' command is used, you can display the following message "No past calculations to show"

Can someone help me, please?

  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

You need to declare function history() and list,

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

Then in the if loop add below code to end of the operations,

last_calculation.append(result)

Then trigger history() function, use 'continue' to make operation after the call history()

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

Answer 2

To save the history, you can add a global variable which is an empty list. Like this:

history = []

...

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


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

This is not the most cleanest solution, but the simplest one since you are only using functions. Ideally functions should not have any side effects and should not depend on the "state" of the program. To save any kind of "state" refactoring this implementation into classes would make things more clean. Something like

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)
        ...

Tips

Make your life simpler by using the standard library

1. The operator library provides functions like add , sub , mul etc.
2. The cmd.Cmd class can be used to build interactive consoles easily.

Answer 3

strong text This is my answer to the problem you face. I have created this and checked it.

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

    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")
    exit()