Prevent blank line at the end of a text file-CodePudding

I have created a program in python that uses a .txt file as a database, so I save the user data there. The data is stored in the file as follows:

Each line in the file represents a user
Users are stored as: User_ID,First Name,Last Name,Phone Number,Country

The problem arises when I try to delete a user that is in the last position of the file, because it leaves a blank line that breaks the function of listing the users in the program.

Example:

Suppose I have two users in the text file: image1

And now I delete the last user (00002): image2

So, there is a blank line, and when I add a new user, it looks like this: image3

Here is the code I use to delete users:

def delete_user(file, user_id):

    with open(file, 'r ') as f:
        users = f.readlines()
        f.seek(0)
        for user in users:
            if user.split(',')[0] != user_id:
                f.write(user)

        f.truncate()

Code I use to add users:

def add_user(file, first_name, last_name, phone_number, country):

    filesize = os.path.getsize(file)

    with open(file, 'r ') as f:
        if filesize == 0:
            f.write(f'{"1".zfill(5)},{first_name},{last_name},{phone_number},'
                    f'{country}')
        else:
            last_line = f.readlines()[-1]
            user_id = int(last_line.split(',')[0])
            f.write(f'\n{str(user_id 1).zfill(5)},{first_name},{last_name},'
                    f'{phone_number},{country}')

Upon investigation, I realized that the problem occurs because there is a newline character (\n) left at the end of the last line, which should not be there. So, how could I solve this problem?

CodePudding user response：

A trailing newline shouldn't break your program. You seem to be using a newline as a line separator, but on Unix-like OSs, a newline is actually considered a line terminator, meaning there should be one at the end of every line.

However, you'll have a much easier time by using a standard data format. What you're using resembles CSV, so I recommend csv.DictReader and csv.DictWriter, which would also involve putting a column header in the file to label the fields. You might also consider using Pandas (e.g. pandas.read_csv() and df.to_csv()).