Sentry Answers>Python>

Write a list to a file in Python with each item on a new line

Write a list to a file in Python with each item on a new line

David Y.

The ProblemJump To Solution

I have a list that looks like this:

Click to Copy
fruits = ["Apples", "Oranges", "Pears", "Bananas", "Pineapples"]

How can I write the contents of this list to a file such that each item appears on its own line? In other words, I want a file that looks like this:

Click to Copy
Apples Oranges Pears Bananas Pineapples

The Solution

We can do this using Python’s str.join method, which takes a list and returns a string containing each list item separated by the string it was called on. Here’s how we might use it to write a list to a file:

Click to Copy
fruits = ["Apples", "Oranges", "Pears", "Bananas", "Pineapples"] with open("fruits.txt", mode="w") as fruitfile: fruitfile.write("\n".join(fruits) + "\n")

fruits.txt will contain the following lines:

Click to Copy
Apples Oranges Pears Bananas Pineapples

We’ve added a new line at the end of the file to respect POSIX conventions, which stipulate that all lines should end with newline characters. This will also make it easier to append additional lines to the file in the future.

join will throw a TypeError if it comes across items in the list that aren’t strings. We can avoid this error by converting all elements of our list to strings using a list comprehension:

Click to Copy
numbers = [1, 2, 3, 4, 5] with open("fruits.txt", mode="w") as numberfile: numberfile.write("\n".join(str(n) for n in numbers) + "\n")
  • Sentry BlogPython Performance Testing: A Comprehensive Guide
  • Sentry BlogLogging in Python: A Developer’s Guide
  • Syntax.fm logo
    Listen to the Syntax Podcast

    Tasty treats for web developers brought to you by Sentry. Get tips and tricks from Wes Bos and Scott Tolinski.

    SEE EPISODES

Loved by over 4 million developers and more than 90,000 organizations worldwide, Sentry provides code-level observability to many of the world’s best-known companies like Disney, Peloton, Cloudflare, Eventbrite, Slack, Supercell, and Rockstar Games. Each month we process billions of exceptions from the most popular products on the internet.

© 2024 • Sentry is a registered Trademark
of Functional Software, Inc.