Data Designer Lambda Column Plugin

A plugin for data-designer that allows you to define columns using custom Python functions. This enables you to inject logic, transformations, and computations directly into your data generation pipeline.

Features

• Row-wise Operations: Apply a function to each row (similar to pandas.DataFrame.apply(axis=1)).
• Full DataFrame Operations: Apply transformations to the entire DataFrame (e.g., exploding lists, aggregations, filtering, pivoting).
• Dependency Management: Explicitly declare required columns to ensure execution order.

Installation

This plugin is designed to be used with data-designer.

pip install data-designer-lambda-column

Usage

Basic Row-wise Transformation

Use operation_type="row" (default) to calculate values based on other columns in the same row.

from data_designer_lambda_column.plugin import LambdaColumnConfig
from data_designer.essentials import DataDesignerConfigBuilder, SamplerColumnConfig, CategorySamplerParams

builder = DataDesignerConfigBuilder()

# 1. Add some base data
builder.add_column(
    SamplerColumnConfig(
        name="quantity",
        sampler_type="category",
        params=CategorySamplerParams(values=[10, 20, 30]),
    )
)

builder.add_column(
    SamplerColumnConfig(
        name="price",
        sampler_type="category",
        params=CategorySamplerParams(values=[5.0, 10.0]),
    )
)

# 2. Add a computed column using a lambda function
builder.add_column(
    LambdaColumnConfig(
        name="total_cost",
        required_cols=["quantity", "price"],
        operation_type="row",  # default
        column_function=lambda row: row["quantity"] * row["price"]
    )
)

Advanced Full DataFrame Transformation

Use operation_type="full" when you need to change the shape of the DataFrame (e.g., explode, melt) or perform operations that require the full context.

Note: When using operation_type="full", your function receives the entire DataFrame and must return the modified DataFrame.

Warning: Operations that change the number of rows (like explode) may not work as expected in the current version due to validation checks on update records in data_designer.

from data_designer_lambda_column.plugin import LambdaColumnConfig
from data_designer.essentials import DataDesignerConfigBuilder

# Define a function to explode a list column
def explode_items(df):
    # Assume 'items_list' is a column containing lists of items
    # e.g., [['apple', 'banana'], ['orange']]
    
    # Explode the list so each item gets its own row
    expanded_df = df.explode("items_list")
    
    # Ensure dependencies are met
    # The new column name 'single_item' must exist in the returned DataFrame
    expanded_df["single_item"] = expanded_df["items_list"]
    
    return expanded_df

builder.add_column(
    LambdaColumnConfig(
        name="single_item",
        required_cols=["items_list"],
        operation_type="full",
        column_function=explode_items
    )
)

Configuration

LambdaColumnConfig accepts the following parameters:

Parameter	Type	Default	Description
name	str	Required	The name of the column to generate.
column_function	callable	Required	The Python function to execute.
required_cols	list[str]	[]	List of column names that must exist before this column is generated.
operation_type	Literal["row", "full"]	"row"	Type of operation. "row" passes a Series (row) to the function. "full" passes the entire DataFrame.

Plugin Registration

This package exposes a standard data_designer plugin entry point:

• Entry Point: data_designer.plugins
• Name: lambda-column
• Impl: data_designer_lambda_column.plugin.LambdaColumnGenerator

It will be automatically discovered by data-designer when installed in the same environment.