Need help for my school assignment (string manipulation)

Question

QUESTIoN: Write a sentence with at least eight words, and assign it to a variable. This will be the text your program works on.

Create a string with every letter that appears at least twice in the sentence. The letters should be in the order of their first appearance in the sentence. Each letter can appear only once in the string. All letters should be in lowercase.

Print the original sentence to the screen, and then the string of letters.

Example:
Input: Democracy is the worst form of government, except for all the others.
Output: emocrasthfnl

My code:Help for school (by Eric Wang)

Answer 1

Eric Wang , it makes it easier to check for us, when you put the code in playground and link it here. Thanks!

Answer 2

Eric Wang

It's a link of your problem. You need to share the link of your code.

Answer 3

https://code.sololearn.com/cFy0NCGyjxsP/?ref=app
Eric Wang

Answer 4

Marc wow, really clever solution, thank you very much for your help !