Write a String to a File on a New Line every time in Python

# Table of Contents

1. Write a string to a file on a new line every time in Python
2. Adding the newline character directly into the string
3. Using a for loop to write a list of strings to a file on new lines
4. Write a string to a file on a new line every time using join()
5. The issues around using the older open() syntax

# Write a string to a file on a new line every time in Python

To write a string to a file on a new line every time:

1. Open the file in writing mode.
2. Append a newline (\n) character to the end of each string.
3. Use the file.write() method to write the lines to the file.

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# ✅ Newer syntax (better)

with open('example.txt', 'w', encoding='utf-8') as my_file:
    my_file.write('first line' + '\n')
    my_file.write('second line' + '\n')
    my_file.write('third line' + '\n')

# -----------------------------------------------------

# ✅ Older syntax (not recommended)

file = open('example.txt', 'w', encoding='utf-8')

file.write('first line' + '\n')
file.write('second line' + '\n')
file.write('third line' + '\n')

file.close()

If you run the code sample, you'd create an example.txt file with the following contents.

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first line
second line
third line

We used the with statement to open the file in reading mode.

The statement automatically takes care of closing the file for us.

We used the addition (+) operator to add a newline (\n) character to the end of each line.

# Adding the newline character directly into the string

If you are writing string literals to the file, add the \n character directly at the end of each string.

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with open('example.txt', 'w', encoding='utf-8') as my_file:
    my_file.write('bobby\n')
    my_file.write('hadz\n')
    my_file.write('com\n')

# Using a formatted string literal instead

Conversely, if you need to interpolate variables in a string, use a formatted string literal.

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with open('example.txt', 'w', encoding='utf-8') as my_file:
    var1 = 'bobby'
    var2 = 'hadz'
    var3 = 'com'

    my_file.write(f'First line: {var1}\n')
    my_file.write(f'Second line: {var2}\n')
    my_file.write(f'Third line: {var3}\n')

The output looks as follows.

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First line: bobby
Second line: hadz
Third line: com

Formatted string literals (f-strings) let us include expressions inside of a string by prefixing the string with f.

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var1 = 'bobby'
var2 = 'hadz'

result = f'{var1}{var2}'
print(result)  # 👉️ bobbyhadz

Make sure to wrap expressions in curly braces - {expression}.

# Using a for loop to write a list of strings to a file on new lines

Use a for loop if you need to write a list of strings to a file on a new line every time.

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with open('example.txt', 'w', encoding='utf-8') as my_file:
    a_list = ['bobby', 'hadz', 'com']

    for item in a_list:
        my_file.write(f'{item}\n')

We used a for loop to iterate over the list, added a newline character to the end of each item and wrote the result to a file.

# Defining a reusable function

If you have to do this often, define a reusable function.

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def write_on_separate_lines(file_name, lines):
    with open(file_name, 'w', encoding='utf-8') as file:
        for line in lines:
            file.write(f'{line}\n')


write_on_separate_lines(
    'example.txt',
    ['bobby', 'hadz', 'com']
)

The function takes a file name and a list of lines as parameters and writes the lines to the file, appending a newline character at the end of each line.

# Write a string to a file on a new line every time using join()

You can also use the str.join() method to write a string to a file on a new line every time.

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with open('example.txt', 'w', encoding='utf-8') as my_file:
    a_list = ['bobby', 'hadz', 'com']

    a_str = '\n'.join(a_list)

    my_file.write(f'{a_str}\n')

The str.join() method takes an iterable as an argument and returns a string which is the concatenation of the strings in the iterable.

If your iterable contains numbers or other types, convert all of the values to strings before calling join().

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with open('example.txt', 'w', encoding='utf-8') as my_file:
    a_list = ['bobby', 1, 'hadz', 2, 'com']

    a_str = '\n'.join(map(str, a_list))

    my_file.write(f'{a_str}\n')

We joined the strings in the list with a newline separator to write them to a file on separate lines.

# The issues around using the older open() syntax

You can also use the older syntax that requires you to manually close the file.

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file = open('example.txt', 'w', encoding='utf-8')

file.write('first line' + '\n')
file.write('second line' + '\n')
file.write('third line' + '\n')

file.close()

The code sample writes the strings to the file on new lines, however, we have to manually close the file after we're done.

On the other hand, the with open() statement takes care of automatically closing the file even if an error is raised.

Calling the file.write() method without using the with statement or calling file.close() might result in the arguments of file.write() not being completely written to the disk.

The newer with open() syntax is a much better option and should be your preferred approach.

# Additional Resources

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