在pyspark中为datafram生成模式定义的编码问题

Question

我想从一个XML文件生成一个模式定义，为我们的笔记本生成一个部署后测试。你知道吗

我已将XML解析为以下字符串：

StructType([StructField('ItemNumber', StringType(), True),
            StructField('UPC', StringType(), True),
            StructField('AssignDate', DateType(), True),
            StructField('AssignmentQuantity', IntegerType(), True)]

把我的数据输入表格：

[Row(dataRow="'A123456', '12345678900', '12/01/2020', 89"),
 Row(dataRow="'B123456','00123456789', 12/02/2018, 1002")]

代码如下：

# create a dataframe from mock test data
def CreateMockInputData(notebook_Name, entity_Name, dataSpec):
    schema = CreateEntitySchema(notebook_Name=notebook_Name, dataSpec=dataSpec, entity_Name=entity_Name)
    print(schema)
    # parse out the data
    entityDef = NotebookEntity(notebook_Name=notebook_Name, dataSpec=dataSpec, entity_Name=entity_Name)
    data_list = entityDef.selectExpr("explode(data_row) as dataRow").collect()
    print()
    print(data_list)
    entity_data = spark.createDataFrame(data_list, schema)
    return entity_data


mock_df = CreateMockInputData(notebook_Name='Test Notebook', dataSpec=df_entityDataDefinitions,
                              entity_Name='entity_for_data'))

我得到的是以下错误：

ParseException                            Traceback (most recent call last)
<command-4322020421037787> in <module>()
----> 1 mock_df = CreateMockInputData(notebook_Name = 'Test Notebook', dataSpec = df_entityDataDefinitions, entity_Name = 'entity_for_data')
      2 #print(mock_df)
      3 mock_df.printSchema()
      4 mock_df.show(10, False)

<command-4322020421037786> in CreateMockInputData(notebook_Name, entity_Name, dataSpec)
     10   print()
     11   print(data_list)
---> 12   entity_data = spark.createDataFrame(data_list, schema)
     13   entity_data = entityData_list
     14   return entity_data

/databricks/spark/python/pyspark/sql/session.py in createDataFrame(self, data, schema, samplingRatio, verifySchema)
    735 
    736         if isinstance(schema, basestring):
--> 737             schema = _parse_datatype_string(schema)
    738         elif isinstance(schema, (list, tuple)):
    739             # Must re-encode any unicode strings to be consistent with StructField names​

我不清楚如何或者什么需要“重新编码”才能让模式与我的数据一起工作。你知道吗

任何建议都会受到欢迎。你知道吗

Answer 1

为了转换定义模式的字符串，您需要使用eval语句执行该字符串。你知道吗

示例：

； schema_str = "StructType([StructField('ItemNumber', StringType(), True), StructField('UPC', StringType(), True), StructField('AssignDate', DateType(), True), StructField('AssignmentQuantity', IntegerType(), True)]" entity_data = spark.createDataFrame(data_list,eval(schema)) ；

；