Plaster

1.1.2 · active · verified Sat Apr 11

Plaster is a loader interface designed to abstract away multiple configuration file formats. It provides a common API for applications to load settings, supporting pluggable loaders discovered via entrypoints. The library focuses on providing a basic interface, leaving specific constraints and implementations to these pluggable loaders. The current version is 1.1.2, released in November 2022, and it is actively maintained by the Pylons Project.

Warnings

breaking Version 1.1 of Plaster dropped support for older Python versions (2.7, 3.4, 3.5, 3.6). Projects on these Python versions must either upgrade their Python environment or pin Plaster to a version older than 1.1.
Fix: Upgrade Python to 3.7+ or pin `plaster<1.1`.
breaking In version 1.1, Plaster switched from `setuptools`/`pkg_resources` to `importlib.metadata` for entry point discovery. While this generally improves performance and reduces runtime dependencies, it might impact advanced use cases that directly interact with entry point mechanisms previously relying on `pkg_resources`.
Fix: Review any custom entry point handling to ensure compatibility with `importlib.metadata`.
gotcha `plaster.exceptions.MultipleLoadersFound` can be raised if multiple installed loaders match the criteria for a `config_uri`. This ambiguity prevents Plaster from choosing a specific loader.
Fix: Disambiguate the lookup by appending the package name to the scheme in the `config_uri` (e.g., `ini+myapp://config.ini` to use the 'ini' loader from the 'myapp' package).
gotcha Prior to version 1.1.2, if a `config_uri` specified a distribution that lacked the expected entry points, Plaster could crash unexpectedly due to a bad unpacking of tuples. This is now caught and raises a `LoaderNotFound` exception.
Fix: Upgrade to `plaster>=1.1.2` to receive a `LoaderNotFound` exception instead of an unhandled crash.
gotcha The `config_uri` parsing behavior for schemes changed in version 0.5. Schemes are now automatically generated as `file+<ext>` for file paths without an explicit scheme (e.g., `file+ini` instead of just `ini`). Also, the order for absolute lookups changed from `scheme+package` to `package+scheme`.
Fix: Ensure `config_uri`s are formatted according to current specifications, especially for older configurations. Explicitly use `package+scheme` for package-specific loaders.
gotcha Plaster's core functionality relies on external 'loader' plugins (e.g., `plaster_pastedeploy`, `plaster_yaml`) to support specific configuration file formats. Without the relevant plugin installed for a given `config_uri` scheme, Plaster will not be able to load the configuration.
Fix: Install the appropriate `plaster` plugin for the configuration file format you intend to use (e.g., `pip install plaster_pastedeploy` for INI files).

Install

pip install plaster Install stable release

Imports

get_settings
```
from plaster import get_settings
```
Used to load configuration settings from a URI and section.
setup_logging
```
from plaster import setup_logging
```
Configures Python's standard logging module based on the provided configuration URI.
get_loader
```
from plaster import get_loader
```
Finds and returns an ILoader object capable of handling a given configuration URI.
parse_uri
```
from plaster import parse_uri
```
Parses a configuration URI into a PlasterURL object, which can then be used by loaders.

Quickstart

This quickstart demonstrates how to load configuration settings from a URI and configure standard logging using `plaster.get_settings()` and `plaster.setup_logging()`. It shows how to specify a configuration file (like 'development.ini') and a specific section ('myapp') to retrieve settings. To run this, you would typically need a loader plugin (e.g., `pip install plaster_pastedeploy`) and a corresponding config file.

import plaster
import sys

# Example config_uri. In a real app, this might come from command line args or an environment variable.
# For demonstration, we'll use a placeholder. Replace 'development.ini#myapp' with your actual config URI.
# You might need a loader like 'plaster_pastedeploy' installed for .ini files.
config_uri = 'development.ini#myapp'

try:
    # Load settings for a specific section (e.g., 'myapp')
    settings = plaster.get_settings(config_uri, section='myapp')
    print("Loaded settings:", settings)

    # Optionally configure logging based on the config file
    plaster.setup_logging(config_uri)
    print("Logging configured.")

    # Example: Accessing a specific setting
    if 'my_setting_key' in settings:
        print(f"Value of 'my_setting_key': {settings['my_setting_key']}")
    else:
        print("No 'my_setting_key' found in settings.")

except plaster.LoaderNotFound:
    print(f"Error: No loader found for URI '{config_uri}'. Make sure the appropriate plaster plugin (e.g., plaster_pastedeploy) is installed.")
except Exception as e:
    print(f"An error occurred: {e}")

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