envsubst

library0.1.5pypypi✓ verified 86d ago

The `envsubst` library for Python provides functionality to substitute environment variables in a string, mimicking the behavior of the GNU `envsubst` command-line utility. It supports `$VAR` and `${VAR}` style variable expansions, including the use of default values like `${VAR:-default}`. The current version is 0.1.5, with its last release in October 2019, indicating a maintenance-only or inactive development cadence.

devops

pip install envsubst

github ↗package ↗

INSTALL

IMPORT

SIG · ENVSUBST

envsubst

devopspythonv0.1.5

Install

1.5s avg

Import

—

Disk

16MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v0.1.5 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

py 3.10–3.910 runs

installs and imports cleanly · install 0.0s · import 0.000s · 17.8MB

glibc

py 3.10–3.910 runs

installs and imports cleanly · install 1.5s · import 0.000s · 18MB

16MB installed

● package 16MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

envsubst

✓ from envsubst import envsubst

This quickstart demonstrates how to import and use the `envsubst` function to replace environment variables in a string. It covers both basic substitution and using default values when a variable is unset or empty. The example explicitly sets and cleans up environment variables for reproducible results.

import os from envsubst import envsubst # Example 1: Basic substitution os.environ['MY_APP_NAME'] = 'MyAwesomeApp' template_string = "The application name is: ${MY_APP_NAME}." result = envsubst(template_string) print(f"Basic substitution: {result}") # Expected: "The application name is: MyAwesomeApp." # Example 2: Substitution with default value (if variable is unset or empty) # Clear the variable to demonstrate default if 'FEATURE_FLAG' in os.environ: del os.environ['FEATURE_FLAG'] template_with_default = "Feature status: ${FEATURE_FLAG:-disabled}." result_default = envsubst(template_with_default) print(f"With default (unset): {result_default}") # Expected: "Feature status: disabled." os.environ['FEATURE_FLAG'] = 'enabled' result_default_set = envsubst(template_with_default) print(f"With default (set): {result_default_set}") # Expected: "Feature status: enabled." # Clean up environment variables used (good practice for scripts) del os.environ['MY_APP_NAME'] if 'FEATURE_FLAG' in os.environ: del os.environ['FEATURE_FLAG']

envsubst --version

Debug

Known issues

gotchaWhen a referenced environment variable (e.g., `$VAR` or `${VAR}`) is not set or is an empty string, `envsubst` will replace it with an empty string by default, potentially leading to unintended blank values in your output if a default is not specified.

fix

Always use default value syntax (`${VAR:-default}`) if the variable might be unset or empty and a fallback is desired. E.g., `envsubst('${DATABASE_URL:-sqlite:///data.db}')`.

affects: 0.1.0-0.1.5

deprecatedThe `envsubst` library has not seen updates since October 2019. While functional for its stated purpose, it might lack modern features or bug fixes present in more actively maintained alternatives like `varsubst` or `envsub`.

fix

For new projects or if advanced features (e.g., custom resolvers, Rust performance) are required, consider alternatives such as `varsubst` (pip install varsubst) or `envsub` (pip install envsub).

affects: 0.1.0-0.1.5

gotchaThe Python `envsubst` library processes strings in memory. It does not provide direct 'in-place' file modification like the shell command can sometimes appear to (with caveats). Attempting `envsubst < file.txt > file.txt` in shell will truncate the file.

fix

To modify a file, read its content, process with `envsubst`, and then write the result back to the file (or a new file). For shell scripting, use a temporary file or `sponge` for in-place edits.

affects: 0.1.0-0.1.5

Errors

Common errors & fixes

KeyError: 'ENV_VAR_NAME'

Attempting to access an environment variable using `os.environ['ENV_VAR_NAME']` directly, but the variable is not set in the current environment.

fix

When fetching environment variables that might not be set, use `os.environ.get('ENV_VAR_NAME', 'default_value')` to provide a fallback, or ensure the variable is always set before runtime. The `envsubst` function itself will substitute unset variables with empty strings if no default is provided in the template (e.g., `${ENV_VAR_NAME:-default}`).

Command 'envsubst' not found

This error typically indicates that the GNU `envsubst` command-line utility is not installed or not in the system's PATH, rather than an issue with the Python `envsubst` library. It's common on macOS without `gettext` installed.

fix

If you intend to use the Python library, ensure you are importing and calling `envsubst` within your Python code (`from envsubst import envsubst`). If you need the shell command, install `gettext` (e.g., `brew install gettext` on macOS, `sudo apt-get install gettext-base` on Debian/Ubuntu).

Upgrade

Version history

0.1.5latest on PyPI · released Oct 5, 2019

Audit

Dependencies

No dependency data recorded yet.

Agent activity

4 hits · last 30 days

node

Resources

githubhttps://github.com/ashafer01/python-envsubst ↗

packagehttps://pypi.org/project/envsubst/ ↗