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Parameters are a place for you to store variables for your pipeline that can be accessed by any node that needs it, and can be easily changed by changing your environment. Parameters are stored in the repository in yaml files.

https://waylonwalker.com/what-is-kedro/

👆 Unsure what kedro is? Check out this post.

parameters files

You can have multiple parameters files and choose which ones to load by setting your environment. By default kedro will give you a base and local parameters file.

  • conf/base/parameters.yml
  • conf/local/parameters.yml

base

The base environment should contain all of the default values you want to run.








        

# /conf/base/parameters.yml
test_size: 0.2
random_state: 3
features:
  - engines
  - passenger_capacity
  - crew
  - d_check_complete
  - moon_clearance_complete
  - iata_approved
  - company_rating
  - review_scores_rating

NOTE base will always be loaded first.

accessing parameters

Parameters can be accessed through context or through the catalog. Generally when you are working with nodes it will be loaded through the catalog.

Loding with the context.








        

context = session.load_context()
context.params

Loading with the catalog.








        

catalog.load('parameters')

Loading a specific key with the catalog.








        

catalog.load('params:test_size')

using parameters in nodes

Here is an example from the complete spaceflights demo. The entire parameters dict is passed in, then the features key is accessed.








        

def split_data(data: pd.DataFrame, parameters: Dict) -> Tuple:
    """Splits data into features and targets training and test sets.

    Args:
        data: Data containing features and target.
        parameters: Parameters defined in parameters.yml.
    Returns:
        Split data.
    """
    X = data[parameters["features"]]
    y = data["price"]
    X_train, X_test, y_train, y_test = train_test_split(
        X, y, test_size=parameters["test_size"], random_state=parameters["random_state"]
    )
    return X_train, X_test, y_train, y_test

https://waylonwalker.com/kedro-node/

👆 Check out this complete guide to creating kedro nodes.

local

The local parameters by default are in conf/local/parameters.yml. They will override the base parameters in a shallow fashion. If a top level key exists in local, it will override that entire key in your parameters.








        

# /conf/local/parameters.yml
env: local
features:
  - company_rating
  - review_scores_rating

NOTE If you have not explicitly set your environment, local will be the default environment selected to override base.

env

You can also have other environments that override the base environment.








        

# /conf/new/parameters.yml
env: new

NOTE if you use an env local will not be applied

Activating this environment

Following the configuration docs we can activate the environment by setting an environment variable in our shell or passing in --env to our kedro cli command.

Setting an environment variable.








        

export KEDRO_ENV=test

Passing in the env to a kedro cli command.








        

kedro run --env=test

Setting the Environment Variable in python.








        

import os
os.environ['KEDRO_ENV'] = 'new'

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