Hands-on Lab·Python Automation for IT

Python Encodings, Temp Files and Atomic Writes

Two problems that only show up in production. The first is encoding: `read_text()` uses whatever the locale says, which is not necessarily what wrote the file. The second is worse - a script that fails half way through a write leaves a truncated file where the good one used to be. This guide shows both, and the function that makes the second impossible.

Files and Data Formats Guide 15 of 39 Intermediate

Python3.14.4
Control nodeUbuntu 26.04 LTS
Managed hostsRHEL 10.0
requests2.34.2
paramiko5.0.0
pytest9.1.1
PyYAML6.0.3
boto3 / botocore1.43.78
TimeAbout 18 min
Reviewed24 August 2026

Written against the versions above. **PEP 540** means the C locale now enables UTF-8 mode rather than degrading to ASCII, which this guide measures - so the classic locale failure is largely gone. `unlink(missing_ok=True)` needs **3.8**, and `os.replace` has been the portable rename since 3.3.

Everything on this page runs on the control node. Any machine with Python 3 will do.
Server Name	IP Address	OS	Roles	CPU	RAM	HDD
RUNNER01	192.168.0.27	Ubuntu 26.04 LTS	Control node - every script in this path runs here	2 Core	4 GB	50 GB

Before you start

guide 10 - read_text and write_text.
guide 9 covers str against bytes if you want the background.

Which encoding a text file is read with
And what the same bytes decode to
errors=, for data you do not control
A temporary file that cleans itself up
The write that leaves a half-file behind
The atomic version
And on a run that succeeds
Why os.replace and not os.rename

Official sources

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Python Encodings, Temp Files and Atomic Writes

Before you start

Which encoding a text file is read with

And what the same bytes decode to

errors=, for data you do not control

A temporary file that cleans itself up

The write that leaves a half-file behind

The atomic version

And on a run that succeeds

Why os.replace and not os.rename

Official sources