如何从用户指定的 txt 列表中删除行？

Question

Python 101 here. I've created a program for a coffee shop owner to keep track of inventory. Im supposed to "Modify the file by allowing the owner to remove data from the file. Ask the owner to enter a description to remove. If the description exists, remove the coffee name and the quantity. If the description is not found, display the message: That item was not found in the file." So far the advice I have received is to read the file content to a list of lines, filter out the lines I don't want and write the list back to the file.

Here's what I have so far

with open('coffeeInventory.txt', 'w') as f:
    f.write('Blonde Roast=15\n')
    f.write('Medium Roast=21\n')
    f.write('Flavored Roast=10\n')
    f.write('Dark Roast=12\n')
    f.write('Costa Rica Tarrazu=18\n')
    f.close()
sum=0

with open('coffeeInventory.txt', 'r') as f:
    for line in f.readlines():
        sum += int(line.split("=")[1])
        print(line)
f.close()

print('Total Pounds of Coffee= ', sum)

with open('coffeeInventory.txt') as f:
  lineList = f.readlines()
lineList= [line.rstrip('\n') for line in open('coffeeInventory.txt')]
print(lineList)

Answer 1

Perhaps this can get you started

import io

f = io.StringIO()

f.write('Blonde Roast=15\n')
f.write('Medium Roast=21\n')
f.write('Flavored Roast=10\n')
f.write('Dark Roast=12\n')
f.write('Costa Rica Tarrazu=18\n')

f.seek(0)

lineList = f.readlines()

print(lineList)

deleteThis = 'Dark Roast'

newList = [line for line in lineList if deleteThis not in line]

print(newList)

Answer 2

I would go another way from the other answers and actually suggest a JSON file.

Firstly, you have to create a dictionary. Each element in a dictionary has a key and a value.

coffee_inventory = {
    "Blonde Roast": 15
}

You can access the inventory by specifying the name within square brackets.

coffee_inventory["Blonde Roast"]

Output: 15

To add a key and a value to a dictionary all you have to do is specify the key in the square brackets and then an equals sign and the value.

coffee_inventory["Medium Roast"] = 21

Thus, now the dictionary would be as such:

coffee_inventory = {
    "Blonde Roast": 15,
    "Medium Roast": 21
}

You will have to use JSON to save and retrieve the file.

import json

coffee_inventory = {
    "Blonde Roast": 15,
    "Medium Roast": 21
}

# Saving the JSON to a file.
# "indent=4" is for better styling.
with open("inventory.json", "w") as file:
    json.dump(coffee_inventory, file, indent=4)

# Retrieving the JSON.
with open("inventory.json", "r") as file:
    coffee_inventory = json.load(file)

print(coffee_inventory)

Output: {'Blonde Roast': 15, 'Medium Roast': 21}

Lastly to delete a value you just use del . For example to delete "Blonde Roast" you do the following.

del coffee_inventory["Blonde Roast"]

This is all you need to know about JSON and I am sure you can connect everything from this guide to your program and make this even better than before.