(Python) 如何让用户打开文本文件，然后更改整数/数字

我曾问过类似的问题，但没有结果。

我是一名编程新手，只教过一些基本技术。任务的一部分是创建一个食谱程序，我大部分时间都完成了这个程序，只有一个部分阻止我完成。

我应该允许用户调用以前创建的文本文件（我已经完成了这一点），然后在此之后应该显示该文件的内容供他们查看（我也已经完成了这一点），但是用户应该能够重新计算份量，从而更改成分的数量。因此，如果用户输入：“我想要 2 份”，并且 1 份的原始数量是 100 克，那么现在应该输出 200 克。

这真的让我很沮丧，我的老师希望明天能完成这项工作。以下是我应该允许用户执行的操作。

用户应该能够检索食谱并为不同数量的人重新计算成分。

• 程序应要求用户输入人数。

• 程序应输出：

• 菜谱名称

• 新人数

• 修订后的数量以及该人数的单位。

我将在下面发布我的实际代码来展示我到目前为止所做的事情，即允许用户查看和制作新菜谱。但缺少修改后的数量位。

如果代码混乱或无组织，我深表歉意，我对此很陌生。

到目前为止的代码：

#!/usr/bin/env python

import time

def start():

    while True:

        user_input = input("\nWhat would you like to do? " "\n 1) - Enter N to enter a new recipe. \n 2 - Enter V to view an exisiting recipe, \n 3 - Enter E - to edit a recipe to your liking. \n 4 - Or enter quit to halt the program " "\n ")

        if user_input == "N":
            print("\nOkay, it looks like you want to create a new recipe. Give me a moment..." "\n")
            time.sleep(1.5)
            new_recipe()

        elif user_input == "V":
            print("\nOkay, Let's proceed to let you view an existing recipe stored on the computer")
            time.sleep(1.5)
            exist_recipe()

        elif user_input == "E":
            print("\nOkay, it looks like you want to edit a recipe's servings. Let's proceed ")
            time.sleep(1.5)
            modify_recipe()

        elif user_input == "quit":
            return

        else:
            print("\nThat is not a valid command, please try again with the commands allowed ")


def new_recipe():
    new_recipe = input("Please enter the name of the new recipe you wish to add! ")
    recipe_data = open(new_recipe, 'w')
    ingredients = input("Enter the number of ingredients ")
    servings = input("Enter the servings required for this recipe ")

    for n in range (1,int(ingredients)+1):

        ingredient = input("Enter the name of the ingredient ")
        recipe_data.write("\nIngrendient # " +str(n)+": \n")
        print("\n")
        recipe_data.write(ingredient)
        recipe_data.write("\n")
        quantities = input("Enter the quantity needed for this ingredient ")
        print("\n")
        recipe_data.write(quantities)
        recipe_data.write("\n")
        unit = input("Please enter the unit for this quantity (i.e. g, kg) ")
        recipe_data.write(unit)
        print("\n")

    for n in range (1,int(ingredients)+1):
        steps = input("\nEnter step " + str(n)+ ": ")
        print("\n")
        recipe_data.write("\nStep " +str(n) + " is to: \n")
        recipe_data.write("\n")
        recipe_data.write(steps)
    recipe_data.close()

def exist_recipe():
    choice_exist= input("\nOkay, it looks like you want to view an existing recipe. Please enter the name of the recipe required. ")
    exist_recipe = open(choice_exist, "r+")
    print("\nThis recipe makes " + choice_exist)
    print(exist_recipe.read())
    time.sleep(1)

def modify_recipe():
    choice_exist = input("\nOkay, it looks like you want to modify a recipe. Please enter the name of this recipe ")
    exist_recipe = open(choice_exist, "r+")    
    servrequire = int(input("Please enter how many servings you would like "))


start()

EDIT:

下面是创建文本文件（配方）及其输出的示例（该文件称为 bread.txt）输出有点混乱，一旦我能让程序的核心工作，我就会解决这个问题。

创建食谱

What would you like to do? 
 1) - Enter N to enter a new recipe. 
 2 - Enter V to view an exisiting recipe, 
 3 - Enter E - to edit a recipe to your liking. 
 4 - Or enter quit to halt the program 
 N

Okay, it looks like you want to create a new recipe. Give me a moment...

Please enter the name of the new recipe you wish to add! bread.txt
Enter the number of ingredients 3
Enter the servings required for this recipe 1
Enter the name of the ingredient flour


Enter the quantity needed for this ingredient 300


Please enter the unit for this quantity (i.e. g, kg) g


Enter the name of the ingredient salt


Enter the quantity needed for this ingredient 50


Please enter the unit for this quantity (i.e. g, kg) g


Enter the name of the ingredient water


Enter the quantity needed for this ingredient 1


Please enter the unit for this quantity (i.e. g, kg) l



Enter step 1: pour all ingredients into a bowl



Enter step 2: mix together



Enter step 3: put in a bread tin and bake

查看菜谱

What would you like to do? 
 1) - Enter N to enter a new recipe. 
 2 - Enter V to view an exisiting recipe, 
 3 - Enter E - to edit a recipe to your liking. 
 4 - Or enter quit to halt the program 
 V

Okay, Let's proceed to let you view an existing recipe stored on the computer

Okay, it looks like you want to view an existing recipe. Please enter the name of the recipe required. bread.txt

This recipe makes bread.txt

Ingrendient # 1: 
flour
300
g
Ingrendient # 2: 
salt
50
g
Ingrendient # 3: 
water
1
l
Step 1 is to: 

pour all ingredients into a bowl
Step 2 is to: 

mix together
Step 3 is to: 

put in a bread tin and bake

如果输入 V，则输出如下：

这个食谱制作面包.txt

Ingrendient # 1: 
flour
300
g
Ingrendient # 2: 
salt
50
g
Ingrendient # 3: 
water
1
l
Step 1 is to: 

pour all ingredients into a bowl
Step 2 is to: 

mix together
Step 3 is to: 

put in a bread tin and bake

我期待您的回复。

您的食谱文件看起来像这样：

Ingrendient # N: 
{INGREDIENT}
{AMOUNT}
{METRIC}
...
(After N ingredients...)
Step N: 
{INSTRUCTIONS}

所以基本上你想一次读取四行，丢弃第一行，然后将其余的分配给有用的东西。

with open(path_to_recipe) as infile:
    ingredients = []
    while True:
        try:
            sentinel = next(infile) # skip a line
            if sentinel.startswith("Step"):
                # we're past the ingredients, so
                break
            name = next(infile)
            amount = next(infile)
            metric = next(infile)
        except StopIteration:
            # you've reached the end of the file
            break
        ingredients.append({'name':name, 'amount':float(amount), 'metric':metric})
        # use a dictionary for easier access

当我们退出时with block, ingredients将是可以按如下方式使用的字典列表：

for ingredient in ingredients:
    scaled_volume = ingredient['amount'] * scale # double portions? etc...
    print(scaled_volume, ingredient['metric'], " ", ingredient['name'])
# # RESULT IS:
300g flour
50g salt
1l water

您应该能够利用所有这些来完成您的任务！