experimental/cpu/: expandvars-0.12.0 metadata and description
Expand system variables Unix style
author_email | Arijit Basu <sayanarijit@gmail.com> |
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description_content_type | text/markdown |
keywords | expand,system,variables |
license | MIT License Copyright (c) 2019 Arijit Basu Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
maintainer_email | Arijit Basu <sayanarijit@gmail.com> |
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provides_extras | tests |
requires_dist |
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requires_python | >=3 |
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expandvars-0.12.0-py3-none-any.whl
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expandvars
Expand system variables Unix style
Inspiration
This module is inspired by GNU bash's variable expansion features. It can be used as an alternative to Python's os.path.expandvars function.
A good use case is reading config files with the flexibility of reading values from environment variables using advanced features like returning a default value if some variable is not defined. For example:
[default]
my_secret_access_code = "${ACCESS_CODE:-default_access_code}"
my_important_variable = "${IMPORTANT_VARIABLE:?}"
my_updated_path = "$PATH:$HOME/.bin"
my_process_id = "$$"
my_nested_variable = "${!NESTED}"
NOTE: Although this module copies most of the common behaviours of bash, it doesn't follow bash strictly. For example, it doesn't work with arrays.
Installation
Pip
pip install expandvars
Conda
conda install -c conda-forge expandvars
Usage
from expandvars import expandvars
print(expandvars("$PATH:${HOME:?}/bin:${SOME_UNDEFINED_PATH:-/default/path}"))
# /bin:/sbin:/usr/bin:/usr/sbin:/home/you/bin:/default/path
Examples
For now, refer to the test cases to see how it behaves.
TIPs
nounset=True
If you want to enable strict parsing by default, (similar to set -u
/ set -o nounset
in bash), pass nounset=True
.
# All the variables must be defined.
expandvars("$VAR1:${VAR2}:$VAR3", nounset=True)
# Raises UnboundVariable error.
NOTE: Another way is to use the
${VAR?}
or${VAR:?}
syntax. See the examples in tests.
EXPANDVARS_RECOVER_NULL="foo"
If you want to temporarily disable strict parsing both for nounset=True
and the ${VAR:?}
syntax, set environment variable EXPANDVARS_RECOVER_NULL=somevalue
.
This helps with certain use cases where you need to temporarily disable strict parsing of critical env vars, e.g. in testing environment, without modifying the code.
e.g.
EXPANDVARS_RECOVER_NULL=foo myapp --config production.ini && echo "All fine."
WARNING: Try to avoid
export EXPANDVARS_RECOVER_NULL
because that will disable strict parsing permanently until you log out.
Customization
You can customize the variable symbol and data used for the expansion by using the more general expand
function.
from expandvars import expand
print(expand("%PATH:$HOME/bin:%{SOME_UNDEFINED_PATH:-/default/path}", environ={"PATH": "/example"}, var_symbol="%"))
# /example:$HOME/bin:/default/path
Contributing
To contribute, setup environment following way:
Then
# Clone repo
git clone https://github.com/sayanarijit/expandvars && cd expandvars
# Setup virtualenv
python -m venv .venv
source ./.venv/bin/activate
# Install as editable including test dependencies
pip install -e ".[tests]"
- Follow general git guidelines.
- Keep it simple. Run
black .
to auto format the code. - Test your changes locally by running
pytest
(pass--cov --cov-report html
for browsable coverage report). - If you are familiar with tox, you may want to use it for testing in different python versions.
Alternatives
- environs - simplified environment variable parsing.