如何添加异常处理以检查用户输入值是否是字典中的键

Question

In my code, i allow the user to enter the key value of the dictionary for them to edit. I would like to make It so the user can only enter those specific values so the dict doesnt get added to. here is my code. need exception handling on variables edit and value.

def edit_items(info):
xy = info
while True:
    print('Index |       Orders')
    for x in range(len(xy)):
        print(x,xy[x])

    choice = int(input('Which entry would you like to edit?\nChoose by index: '))
    print(xy[choice])
    edit = input('What you want to edit: ')   # Key val of dict 
    value = input("Enter: ")    # Value for the specific key in dict
    xy[choice][edit.capitalize()] = value
    print('list updated.')
    print(xy[choice])
    with open('cart.txt','w') as file:
        file.write(str(xy))
    file.close()

    more_edits = input('\nDo you want to make more edits?(y/n): ')
    if more_edits == 'n':
        break
print(xy)

example of output the user sees.

0 {'Item': 'edd', 'Price': '1.0', 'Quantity': '1'}
1 {'Item': 'milk', 'Price': '1.0', 'Quantity': '1'}

Answer 1

I'd love to answer your question:D

Here's the code for it:

def edit_items(info):
    #assuming that info is a dict
    someKey = input("Enter the key to edit the val:")
    if someKey not in info:
        raise "KeyNotFound: <Error Message>"

you're now to use either the 'raise method', or you can use 'try/except' method as well:

def edit_items(info):
    #assuming that info is a dict
    someKey = input("Enter the key to edit the val:")
    try:
        info[someKey] = input("Enter the value for the key:")
    except Exception as e:
        print(e)    

I hope this was a satisfactory answer:D

Answer 2

I expect you want the program to raise an exception. You can do this quite simply.

...
edit = input('What you want to edit: ')   # Key val of dict 

if edit not in xy.keys():
    raise KeyError(f'There is no item called {edit}')  #raises a KeyError

value = input("Enter: ")    # Value for the specific key in dict

xy[choice][edit.capitalize()] = value
...

If you don't want to raise an exception you could do something like this.

...
edit = input('What you want to edit: ')

while edit not in xy.keys():
    print('You can\'t edit that')
    edit = input('What you want to edit: ')

value = input("Enter: ")    # Value for the specific key in dict

xy[choice][edit.capitalize()] = value
...

This code will ask for a new input from the user until the input is valid.