✍️ Writing to Files

Knowing how to write to files with Python can be a very useful skill to have in your engineering career. This section covers the basics of writing to files.

Writing basics

We can write and print information to a new file using the write function as shown below. In this example, we're overwriting the old content of testFile.txt with a new message. The Python code prints the old content of the file, writes a new message, and then prints the new content of the file.

Old Content of testFile.txt

Howdy!
This is a test file!
You're doing great! :)

Code

# Opening a file
myFile = open("testFile.txt", "r+")  # allows reading and writing to a file

# Writing to a file
myFile.write("Tech Affairs is awesome!!")

# Reading our new text
print('\nNew content:\n', myFile.read())

Output

New content:
Tech Affairs is awesome!!

note

If a file with the given filename doesn't exist, a new file with that name will be created.

Append to a file

We can see that the w permission causes Python to overwrite old content from a file, however, if we want to keep the old information and add on to it, we can use the a permission instead of the w as shown below.

Old Content of testFile.txt

Howdy!
This is a test file!
You're doing great! :)

Code

# Opening a file
myFile = open("testFile.txt", "a+")  # allows appending and reading a file

# Writing to the end of a file
myFile.write("This is new content!")

# Reading our new text
print('New content:\n', myFile.read())

Output

New content:
Howdy!
This is a test file!
You're doing great! :)
This is new content!