environ composition

The library for parsing environ configuration and creating nested configuration classes through composition.

• EnvConfigParser is designed to parse environment variables and a .env file to create a structured configuration.
• EnvConfig takes the parsed environment variables (a dictionary) and creates an object with attributes matching the keys.

Installation

pip install environ-composition

Import

from environ_composition import EnvConfigParser

Usage

config = EnvConfigParser(dotenv_path='path_to/.env', separator='__').parse()

In EnvConfigParser each environment variable name goes into a lowercase attribute of EnvConfig instance.

Adding some separator (i.g. double underscores "__") to the variable name adds a level of nesting to the config.

VAR1=value1
VAR2__NESTED_VAR1=nested_value1

config.var1 = "value1" 
config.var2.nested_var1 = "nested_value1"

When specifying a template, the parser updates the values in the template.

Without a template, the parser returns the config in EnvConfig instance.

class NestedTemplate:
    def __init__(self):
        self.nested_var1 = None

class Template:
    def __init__(self):
        self.var1 = None
        self.var2 = NestedTemplate()

template = Template()

parser = EnvConfigParser('path_to/.env')

config = parser.parse(template)

The structure and nesting levels of the template must match the names in the environment variable.

Mismatched names of attributes and private attributes in the template are not updated.

Parsing values

The ast library and the literal_eval function are used for parsing string values.

Standard data types are available: str, int, float, bool, list, tuple, set, dict, etc.

VAR1=['string', 1, 1.01, True]
VAR2__NESTED_VAR1={"string": 1}

For variables with null string values ('', 'None', 'null'), None is assigned.

VAR1=
VAR2=None
VAR3=null

The use_literal_eval flag in the parse method determines to use or not parsing.

Type validation

If there is a type annotation for class attributes, the parser validates the assigned values.

If there is a type annotation for instance attributes, the parser does not validate. If an annotation is specified in the class attributes, the parser will validate the instance attribute.

Validation is not applied to nested config instances.

class NestedTemplate:
    nested_var1: str = None
    
    def __init__(self):
        self.nested_var2 = None # it will not be validated

class Template:
    var1: str = None
    var2: int = None
    var3: NestedTemplate = NestedTemplate() # it will not be validated
    var4: bool
    
    def __init__(self):
        self.var4 = None  
        self.var5 = NestedTemplate() # it will not be validated

The use_type_validation flag in the parse method determines to use or not type validation. Validation only works if use_literal_eval = True.