LayConf - Layered Configuration Parser for Python3

Overview

A simple wrapper over Python's configparsr that reads configuration in the following order:

1. Environment variables
2. Custom configuration ini file (optional)
3. Default configuration ini file (must exist)

Each config option lookup will fallback to next layer if not found in the present layer.

Convention for env. vars is {prefix}_{section}_{option} or {section}_{option} if prefix is empty. For example: LOG_file_backup_count=100

All lookups are case sensitive.
No external dependencies.

Example

First Layer of configuration is cfg/default.ini with all default values:

[LOG]
console_enabled = true
console_level = INFO
file_enabled = true
file_rotation_size_mb = 10
file_backup_count = 1000

[DATABASE]
endpoint =
env_name = default
query_filter =

Second Layer of configuration is cfg/staging.ini, override just what you want to change:

[DATABASE]
env_name = staging
endpoint = staging:3001

Application code:

from layconf import LayConf

# the default config file is cfg/default.ini unless specified other
# custom_config_file_path is an optional layer
# env_prefix is empty by default, which means that environment variable names will be 
# mapped to {section}_{option}
LayConf.init_config(custom_config_file_path="cfg/staging.ini", env_prefix="example")

print("env_name:", LayConf.get("DATABASE", "env_name"))
print("console_enabled:", LayConf.getboolean("LOG", "console_enabled"))
print("file_rotation_size_mb:", LayConf.getint("LOG", "file_rotation_size_mb"))

# dealing with not exist keys
# be default - raise an Error, as it is recommended to keep defaults for all fields in default.ini
try:
    print("foo:", LayConf.get("FOO", "foo"))
except KeyError:
    print("'foo' not found")
# but it is also possible to specify an inline default
print("foo:", LayConf.get("FOO", "foo", fallback="bar"))
print("foo_number:", LayConf.get("FOO", "foo_number", fallback=33))

# also possible to get an entire config section and read from with an indexer
log_section = LayConf.getsection("LOG")
print("file_enabled:", log_section["file_enabled"])
print("file_backup_count:", log_section.getint("file_backup_count"))

Output:

% example_LOG_file_backup_count=300 python example_app.py
config env prefix: example
config default: cfg/default.ini
config custom: cfg/staging.ini
env_name: staging
console_enabled: True
file_rotation_size_mb: 10
'foo' not found
foo: bar
foo_number: 33
file_enabled: true
file_backup_count: 300

ToDo:

• Packaging to pip
• Command-Line arguments layer
• Flexible number of file layers

Credit:

This code is a modified version of https://medium.com/@unpluggedcoder/python-config-parser-compatible-with-environment-variable-8c5c46145a46. Thanks @UnpluggedCoder

License:

Apache-2.0