Check if a variable string exist in a text file

Question

So guys, i'm tryng to make a password generator but i'm having this trouble:

First, the code i use for tests:

idTest= "TEST"
passwrd= str(random.randint(11, 99))


if not os.path.exists('Senhas.txt'):
    txtFileW = open('Senhas.txt', 'w')
    txtFileW.writelines(f'{idTest}: {passwrd}\n')
    txtFileW.close()
else:
    txtFileA = open('Senhas.txt', 'a')
    txtFileA.write(f'{idTest}: {passwrd}\n')
    txtFileA.close()

print(f'{idTest}: {passwrd}')

Well, what i'm expecting is something like this:

else:
    with open('Senhas.txt', 'r+') as opened:
        opened.read()
        for lines in opened:
            if something == idTest:
                lines.replace(f'{something}', f'{idTest}')
            else:
                break
txtFileA = open('Senhas.txt', 'a')
txtFileA.write(f'{idTest}: {passwrd}\n')
txtFileA.close()

print(f'{idTest}: {passwrd}')

I've searched for it but all i've found are ways to separate it in 2 files (for my project it doesn't match) or with "static" strings, that doesn't match for me as well.

@EdwinCruz "something" is actually _something_ in the text file — GabrielO, Jul 07 '20 at 21:26
`opened.replace()` makes no sense. `opened` is a file, it doesn't have a `replace()` method. Did you mean `lines.replace()`? — Barmar, Jul 07 '20 at 21:29
I can't figure out what you're tryhing to do with that loop. Are you trying to replace a user's password with a new password? — Barmar, Jul 07 '20 at 21:30
@Barmar I want that if the "id" alread is in the file; it changes the password — GabrielO, Jul 07 '20 at 21:31
I suspect what you want is something like `if lines.startswith(idTest + ':')` — Barmar, Jul 07 '20 at 21:31
Why are you using a text file instead of a database or JSON? — Barmar, Jul 07 '20 at 21:32

score 0 · Accepted Answer · answered Jul 07 '20 at 21:39

You can use the fileinput module to update the file in place.

import fileinput

with fileinput.input(files=('Senhas.txt'), inplace=True) as f:
    for line in f:
        if (line.startswith(idTest+':'):
            print(f'{idTest}: {passwrd}')
        else:
            print(line)

Check if a variable string exist in a text file

1 Answers1