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Writing to a file in Python

schedule Aug 12, 2023
Last updated
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Python
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Writing to a file once

To write to an external file in Python:

file_name = "names.txt"
with open(file_name, "w") as file:
   file.write("Alex\nBob\nCathy")

We end up with a text file called "names.txt" with the following content:

Alex
Bob
Cathy
WARNING

Writing to a file using the "w" option results in overwrites

In our example, if you had a file called "names.txt" already, then the contents of that file will be overwritten. To append to a file instead, use the "a" option. This option is discussed below.

Writing to a file multiple times

Note that you could also write to a file multiple times:

file_name = "names.txt"
with open(file_name, "w") as file:
   file.write("Alex\n")
   file.write("Bob\n")
   file.write("Cathy")

If you run this, we will end up with the exact same result:

Alex
Bob
Cathy

What's important here is that all your write calls that are under the same with do not overwrite each other.

Appending to a file

Instead of overwriting an existing file, you could append to it.

Suppose we have the following text file called names.txt:

Alex
Bob

To append to this file:

file_name = "names.txt"
with open(file_name, "a") as file:
   file.write("\nCathy")
   file.write("\nDave")

The resulting file is as follows:

Alex
Bob
Cathy
Dave
robocat
Published by Isshin Inada
Edited by 0 others
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