lowercasing function doesn't work in a different function

[gorgenasty]

Please bear with me, I am new to Python.

The first function I wrote was one to lowercase any uppercase characters in a string that passed through it, which works by itself, while ignoring any non-uppercase alphabetical ASCII characters.

However, when I try to use it in my second function, (which SHOULD use the lowercasing function on whatever the user inputs and then sticks it in a file) I'm left with a file that contains the the string that's initially passed through without any of the lowercasing function.

import os.path
from os import path

def lowercaser(text):
text = [ord(c) for c in text]
length = len(text)

i = 0
while length != i:
    if 65 <= text[i] <= 90:
        text[i] = text[i] + 32
    i += 1

text = [chr(c) for c in text]
text = "".join(text)

def does_rfid_list_exist():
if path.exists("rfidList.txt"):
print("File found!")

else:
    print("File was not located! Creating new file.\n")
    f = open("rfidList.txt", "a+")
    user_input = input("Please enter your name!\n")
    lowercaser(user_input)
    f.write(user_input)
    f.close()

does_rfid_list_exist()

I have no idea why they don't work together, and I've broken it down as far as I can. Any ideas?

[JonB]

@gorgenasty

def lowercaser(text):
    text = ...

def does_rfid_list_exist():
    user_input = input("Please enter your name!\n")
    lowercaser(user_input)
    f.write(user_input)

When you pass parameters to methods, Python works on a copy of the variable passed in. If the method changes that variable it does not affect the variable passed in by the caller --- that just retains its original value. So, here your lowercaser() makes its change to a copy of user_input, and all its work is discarded when it returns. When you f.write(user_input) you are saving its original value, from user_input = input().

Your def lowercaser(text) needs to finish with a return text, to return the altered text. And your call needs to be user_input = lowercaser(user_input).

[SGaist]

Hi and welcome to devnet,

Why not just use Python str lower function ?

[JonB]

@SGaist
I assume this is learning exercise! :) He references a learning course he is doing.