Think

Here we are given three files. A ende.py, pw.txt, and flag.txt.en.

Runnning python ende.py -h gives us a list of arguments. In our case we want to decrypt flag.txt.en using -d. It prompts to enter a password, so you just pass the contents of pw.txt.

> python ende.py -d flag.txt.en
Please enter the password: 68f88f9368f88f9368f88f9368f88f93

Solve

And we get the final flag: picoCTF{4p0110_1n_7h3_h0us3_68f88f93}