我问了一个类似的问题，但没有用。
我是一名新手编程学生，我只学过一些基本技巧。部分任务是创建一个我主要完成的配方程序，只有一部分阻止我完成。
我应该允许用户调用以前创建的文本文件（我已完成此位），然后在此之后应该显示该文件的内容供他们查看（我也做了这一点）但是，用户应该能够重新计算份量，从而改变成分的数量。因此，如果用户输入：“我要2份”，1份的原始数量为100g，现在应该输出200g。
这真让我感到沮丧，我的老师明天希望这项工作。以下是我应该允许用户做的事情。
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：
•食谱名称
•新人数
•修订后的数量，包含此人数的单位。
我将在下面发布我的实际代码，以显示我到目前为止所做的工作，即允许用户查看和制作新配方。但缺少修订后的数量。
如果代码混乱或无组织，我很抱歉，我是新手。
到目前为止代码：
#!/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()
修改
下面是一个文本文件（配方）的示例创建及其输出（该文件名为bread.txt）注意输出有点乱，我将修复一旦我可以得到的核心计划工作。
制作食谱
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
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：
，这是输出这个食谱制作了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
我期待你的回复。
答案 0 :(得分：2)
您的配方文件看起来像这样：
Ingrendient # N:
{INGREDIENT}
{AMOUNT}
{METRIC}
...
(After N ingredients...)
Step N:
{INSTRUCTIONS}
所以基本上你想一次读四行，丢弃第一行，然后将其余部分分配给有用的东西。
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with块时，ingredients将是可以按如下方式使用的词典列表：
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
你应该能够利用所有这些来完成作业！