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我有一个数据框的列值，我在其中接收到一个字符串输入，如下所示，其中 startIndex 是每个字符开头的索引，结束索引是字符串中该字符出现的结尾，标志是字符本身。

    +---+------------------+
    | id|    Values        |
    +---+------------------+
    |01 |  AABBBAA         |
    |02 |  SSSAAAA         |
    +---+------------------+

现在我想将字符串转换为每一行的字典，如下所示：

    +---+--------------------+
    | id|    Values          |
    +---+--------------------+
    |01 |  [{"startIndex":0, |
    |   |    "endIndex" : 1, | 
    |   |    "flag" : A },   |
    |   |   {"startIndex":2, |
    |   |    "endIndex" : 4, |
    |   |    "flag" : B },   |
    |   |   {"startIndex":5, |
    |   |    "endIndex" : 6, |
    |   |    "flag" : A }]   |
    |02 |  [{"startIndex":0, |
    |   |    "endIndex" : 2, |
    |   |    "flag" : S },   |
    |   |   {"startIndex":3, |
    |   |    "endIndex" : 6, |
    |   |    "flag" : A }]   |
    +---+--------------------+-

我有伪代码来构建字典，但不确定如何在不使用循环的情况下一次将其应用于所有行。此外，这种方法的问题是只有最后一个框架字典在所有行中被覆盖


        import re
        x = "aaabbbbccaa"
        xs = re.findall(r"((.)\2*)", x)
        print(xs)
        start = 0
        output = '' 
        for item in xs:
            end = start + (len(item[0])-1)
            startIndex = start
            endIndex = end
            qualityFlag = item[1]
            print(startIndex, endIndex, qualityFlag)
            start = end+
4

1 回答 1

1

使用udf( )包装代码逻辑并使用 to_json()将结构数组转换为字符串：

from pyspark.sql.functions import udf, to_json
import re

df = spark.createDataFrame([
      ('01', 'AABBBAA')
    , ('02', 'SSSAAAA')
  ] , ['id', 'Values']
)

# argument `x` is a StringType() over the udf function
# return `row` as a list of dicts
@udf('array<struct<startIndex:long,endIndex:long,flag:string>>')
def set_fields(x):
    row = []
    for m in re.finditer(r'(.)\1*', x):
        row.append({
            'startIndex': m.start()
          , 'endIndex': m.end()-1
          , 'flag': m.group(1)
        })
    return row

df.select('id', to_json(set_fields('Values')).alias('Values')).show(truncate=False)
+---+----------------------------------------------------------------------------------------------------------------------------+
|id |Values                                                                                                                      |
+---+----------------------------------------------------------------------------------------------------------------------------+
|01 |[{"startIndex":0,"endIndex":1,"flag":"A"},{"startIndex":2,"endIndex":4,"flag":"B"},{"startIndex":5,"endIndex":6,"flag":"A"}]|
|02 |[{"startIndex":0,"endIndex":2,"flag":"S"},{"startIndex":3,"endIndex":6,"flag":"A"}]                                         |
+---+----------------------------------------------------------------------------------------------------------------------------+
于 2019-09-25T02:17:27.957 回答