Python3如何从列表中检索列表

Question

I want to create a user-defined input that retrieves the list within the list of stk_pairs.

For example, when the input prompts the user to select which pair they want, eg 1, it means that it will retrieve the second element of the stk_pairs list; in this case is [ 'C', 'D']

stk_pairs = [['A, B'],
              ['C', 'D'],
              ['E', 'F']]

print('1st pair is A and B; indicated as 0')
print('2nd pair is C and D; indicated as 1')
print('3rd pair is E and F; indicated as 2')

get_stk_pairs = input('choose which pair to compare: ')
answer = stk_pairs[get_stk_pairs]
print(answer)

However, I get this error:

Output

TypeError: string indices must be integers

Please advise!

Answer 1

You should make sure that the input value will be an int type to be accepted as the index of your list while by default the input is a str . So your code should be changed to this:

get_stk_pairs = int(input('choose which pair to compare: '))

Answer 2

You need to convert the user input to int (as by default it is of type str ) so that can be used as an index in retrieving the elements from the list:

get_stk_pairs = int(input('choose which pair to compare: '))