创建 Expectations

使用 Great Expectations 的数据质量入门

Davina Moossazadeh

Data Scientist

Expectations

Expectation：关于数据的可验证断言

列级 Expectations
形状与架构（schema）Expectations
- schema：数据集结构的蓝图

¹ https://docs.greatexpectations.io/docs/reference/learn/terms/expectation

Expectations

Expectation：关于数据的可验证断言

列级 Expectations
形状与架构（schema）Expectations
- schema：数据集结构的蓝图

¹ https://docs.greatexpectations.io/docs/reference/learn/terms/expectation

可再生能源发电数据集

一个包含可再生能源发电数据的 pandas DataFrame，列包括："Time""Energy delta[Wh]""GHI""temp""pressure""humidity""wind_speed""rain_1h""snow_1h""clouds_all"。该 DataFrame 有 118,066 行。

¹ https://www.kaggle.com/datasets/pythonafroz/renewable-power-generation-and-weather-conditions

创建一个 Expectation

gx.expectations.Expect...(...)

GX 类（Expectations）：PascalCase

GX 函数/方法：snake_case

¹ https://docs.greatexpectations.io/docs/core/define_expectations/create_an_expectation/

创建一个 Expectation

row_count_expectation = gx.expectations.ExpectTableRowCountToEqual(

    value=118000
)

validation_results = batch.validate(

    expect=row_count_expectation
)

¹ https://docs.greatexpectations.io/docs/core/define_expectations/create_an_expectation/ https://docs.greatexpectations.io/docs/core/define_expectations/test_an_expectation/

评估一个 Expectation

print(validation_results)

{ 
    "success": false,
    "expectation_config": {
        "type": "expect_table_row_count_to_equal",
        "kwargs": {"batch_id": "my_pandas_datasource-my_dataframe_asset", "value": 118000},
        "meta": {},
        "rendered_content": [{"name": "atomic.prescriptive.summary", "value": {"schema": {"type": "com.superconductive.rendered.string"}, "template": "Must have exactly $value rows.", "params": {"value": {"schema": {"type": "number"}, "value": 118000}}}, "value_type": "StringValueType"}]
    },
    "result": {"observed_value": 118066},
    "meta": {},
    "exception_info": {"raised_exception": false, "exception_traceback": null, "exception_message": null},
    "rendered_content": [{"name": "atomic.diagnostic.observed_value", "value": {"schema": {"type": "com.superconductive.rendered.string"}, "template": "118066", "params": {}}, "value_type": "StringValueType"}]
}

¹ https://docs.greatexpectations.io/docs/core/run_validations/run_a_validation_definition/

评估一个 Expectation

print(validation_results.describe())

{
    "expectation_type": "expect_table_row_count_to_equal",
    "success": false,
    "kwargs": {
        "batch_id": "my_pandas_datasource-my_dataframe_asset",
        "value": 118000
    },
    "result": {
        "observed_value": 118066
    }
}

评估一个 Expectation

print(validation_results.success)

False

print(validation_results["success"])

False

评估一个 Expectation

print(validation_results.result)

{'observed_value': 118066}

print(validation_results["result"])

{'observed_value': 118066}

其他常见 Expectations

形状类 Expectations：

ExpectTableRowCountToEqual(value: int)
ExpectTableRowCountToBeBetween(
    min_value: int, max_value: int
)
ExpectTableColumnCountToEqual(
    value: int
)
ExpectTableColumnCountToBeBetween(
    min_value: int, max_value: int
)

列名类 Expectations：

ExpectTableColumnsToMatchSet(
    column_set: set
)
ExpectColumnToExist(column: str)

速查表

创建一个 Expectation：

gx.expectations.Expect...(...)

验证一个 Expectation：

validation_results = batch.validate(
    expect=expectation
)

创建行数 Expectation：

expectation = gx.expectations. \
ExpectTableRowCountToEqual(
    value: int
)

查看验证结果：

validation_results.describe()
validation_results.success
validation_results.result

Passons à la pratique !

使用 Great Expectations 的数据质量入门