Listing file names present in a directory without using import os

I am attempting to create a program allowing new user creation on python. However already created users get overwritten if the name of the new profile is the same as the old one, this is because a new text file is created with the selected username as the title, so the new text file replaces the old one.

Due to restrictions on my system I am unable to use import os, so I need an alternative method to list all the file names present in a directory or subdirectory, so they can be compared to the new username and cancel the user creation if a file with that name already exists to prevent users being overwritten.

Snippet of my code:

new_username=str(input('Please choose a username : '))
new_password=str(input('Please choose a password : '))
print("Good Choice!")

title=new_username + '.txt'           #Creating title of the file
file=open(title,'w')                  #Creating the file
file.write(new_password)              #Adding password to the file
file.close()

print("User succesfuly created!!")

This part all runs fine, I just need a way to prevent it from overwriting other users.

Thank you for your time :)

Solution

You can open with mode 'x': "open for exclusive creation, failing if the file already exists".

try:
    with open(title, 'x') as file:              
        file.write(new_password)
    print("User successfully created!!")
except FileExistsError:
    print("User already exists!!")

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