parameter-expansion-patched

0.3.1 verified Fri May 01 auth: no python

A Python library that implements shell-style parameter expansion (e.g., ${VAR:-default}, ${VAR#prefix}). It is a patched fork of the original parameter-expansion library, maintained for PyPI distribution. Current version 0.3.1, with occasional updates.

pip install parameter-expansion-patched

Common errors

error ModuleNotFoundError: No module named 'parameter_expansion' ↓

cause Importing the old package name instead of the patched version.

fix

Install parameter-expansion-patched and import from parameter_expansion_patched.

error AttributeError: 'ParameterExpander' object has no attribute 'expand' ↓

cause Using the class from the original unpatched library which has a different API.

fix

Ensure you are using parameter_expansion_patched (version 0.3.1) and that the class has an 'expand' method.

Warnings

gotcha The expander does NOT access the actual OS environment by default. You must pass a dict or use os.environ explicitly. Failing to do so may lead to empty expansions. ↓

fix If you want to use the real environment, pass os.environ: ParameterExpander(env=os.environ).

gotcha The library only supports a subset of shell parameter expansion features. Known missing: ${!indirect}, ${parameter:offset:length}, ${parameter/pattern/string} substitution. ↓

fix Check the documentation for supported syntax before relying on advanced patterns.

Imports

ParameterExpander
wrong
```
from parameter_expansion import ParameterExpander
```
correct
```
from parameter_expansion_patched import ParameterExpander
```
The original library is unmaintained; use the patched version with the underscored package name.

Quickstart

Creates a ParameterExpander with an environment dict, then expands a string with shell parameter syntax.

from parameter_expansion_patched import ParameterExpander

expander = ParameterExpander(env={'USER': 'alice', 'HOME': '/home/alice'})
result = expander.expand('Hello ${USER:-default}, your home is ${HOME}')
print(result)  # Hello alice, your home is /home/alice