Data Asset Features Guide

This document describes useful features of the DataAsset object. A DataAsset in Great Expectations is the root class that enables declaring and validating expectations; it brings together data and expectation evaluation logic.

Interactive Evaluation

Setting the interactive_evaluation flag on a DataAsset make it possible to declare expectations and store expectations without immediately evaluating them. When interactive evaluation is disabled, the running an expectation method on a DataAsset will return the configuration just added to its expectation suite rather than a result object.

At initialization

>> import great_expectations as ge
>> import pandas as pd
>> df = pd.read_csv("./tests/examples/titanic.csv")
>> ge_df = ge.dataset.PandasDataset(df, interactive_evaluation=False)
>> ge_df.expect_column_values_to_be_in_set('Sex', ["male", "female"])

{
    'stored_configuration': {
        'expectation_type': 'expect_column_values_to_be_in_set',
        'kwargs': {
            'column': 'Sex',
            'value_set': ['male', 'female'],
            'result_format': 'BASIC'
        }
    }
}

Dynamically adjusting interactive evaluation

>> import great_expectations as ge
>> import pandas as pd
>> df = pd.read_csv("./tests/examples/titanic.csv")
>> ge_df = ge.dataset.PandasDataset(df, interactive_evaluation=True)
>> ge_df.expect_column_values_to_be_in_set('Sex', ["male", "female"])

{
    'success': True,
    'result': {
        'element_count': 1313,
        'missing_count': 0,
        'missing_percent': 0.0,
        'unexpected_count': 0,
        'unexpected_percent': 0.0,
        'unexpected_percent_nonmissing': 0.0,
        'partial_unexpected_list': []
    }
}

>> ge_df.set_config_value("interactive_evaluation", False)
>> ge_df.expect_column_values_to_be_in_set("PClass", ["1st", "2nd", "3rd"])

{
  'stored_configuration': {
    'expectation_type': 'expect_column_values_to_be_in_set',
    'kwargs': {
      'column': 'PClass',
      'value_set': [
        '1st',
        '2nd',
        '3rd'
      ],
      'result_format': 'BASIC'
    }
  }
}