CertGrid CertGrid
Hands-on Lab·Python Automation for IT

Python Process Environment and Working Directory

A child process starts with a copy of your environment and your working directory. Both can be set per child, and both have a trap: `env=` **replaces** the whole environment rather than adding to it, so a child given one variable has no `HOME` and a `PATH` it did not expect; and `os.chdir` changes the directory for everything after it, whereas `cwd=` affects only that one child.

OS and Process Automation Guide 19 of 39 Intermediate

Written against the versions above. Nothing on this page is version-dependent. `os.environ` has behaved this way since Python 2 and `cwd=` has been a `subprocess` argument from the start.

Everything on this page runs on the control node. Any machine with Python 3 will do.
Server NameIP AddressOSRolesCPURAMHDD
RUNNER01192.168.0.27Ubuntu 26.04 LTSControl node - every script in this path runs here2 Core4 GB50 GB

Before you start

  1. A child inherits the environment

  2. env= replaces rather than adds

  3. The working directory a child gets

  4. So prefer cwd= over os.chdir

  5. What a process knows about itself

Official sources

← All Python Automation guides