can someone give me some tips on how to make Python programs that write data to external files?

[danniltrifonov]

so lately i've been learning about making Python programs that write to text files. and I made an example of such (in this we assume in the directory theres a file called "database.txt")

file = open("database.txt","r+")
name = input("Enter your name: ")
age = int(input("Enter your age: "))

def is_minor(age):
    is_minor = False
    if age > 18:
        is_minor = True
    else:
        is_minor = False
    return is_minor

minor = is_minor(age)

def write_to_file(name, age, file, minor):
    file.write(name + ", "
    file.write(str(age) + ", ")
    file.write(minor)

write_to_file(name, age, file, minor)
file.close()

and now my problem with this is: it does actually work, it writes allow 4 values to the txt file, but everytime it runs it gets rid of what was there before. I don't know if that means that i'm using the wrong file.open("database.txt,"r+"). maybe the "r+" isn't for appending. honestly the problem is likely the file.write statement, so if anyone knows what file.write() statement i could use to append information to the file without overriding the contents, that would be amazing.

[Links]

1. Wrong logic in is_minor()

You wrote:

if age > 18:
    is_minor = True
else:
    is_minor = False

This means someone over 18 is considered a minor, which is backwards.
It should be:

if age < 18:
    is_minor = True
else:
    is_minor = False

Or even shorter:

return age < 18

---

2. Missing parenthesis in file.write()

In write_to_file():

file.write(name + ", "

You forgot the closing ) for that file.write call.

---

3. Writing a boolean directly to a file

file.write() needs a string.
You’re trying to write:

file.write(minor)

But minor is a boolean (True or False). You must convert it to string:

file.write(str(minor))

---

4. You’re opening the file with r+

r+ means read/write without truncating. If the file doesn’t exist, it will throw an error. If you just want to append, use "a" or "a+". If you want to overwrite, use "w".

---

Fixed Code

Here’s a working version:

# Open in append mode
file = open("database.txt", "a")

name = input("Enter your name: ")
age = int(input("Enter your age: "))

def is_minor(age):
    return age < 18

minor = is_minor(age)

def write_to_file(name, age, file, minor):
    file.write(name + ", ")
    file.write(str(age) + ", ")
    file.write(str(minor) + "\n")

write_to_file(name, age, file, minor)
file.close()

[Links]

Hope it worked :)

[danniltrifonov]

@Links Thank you so much! I see what your saying, so I need to fix the is_minor logic, I'm forgetting the ")" in the file.write statement, and I need to converrt the Bool from is_minor into a string. And also, thank you you telling me to open it with "a+", I was very confused with that. Thank you again for your help!

[Links]

@danniltrifonov You're welcome!

[TheAndyboi]

theres always chatgpt

[Links]

@Andyboi yeah actually but he sometimes is outdated so its better to just check the forms

[danniltrifonov]

@Links exactly, plus chatgpt doesn't even work that well on the switch

[Links]

@danniltrifonov Yeah and chat gpt cant even write code. it can just correct code

[TheAndyboi]

ive heard chatgpt can write code

[Links]

@Andyboi it can but it always glitches and gives LOADS OF error messages. (The code)