在 PySpark 中爆炸 [英] Explode in PySpark

问题描述

我想从包含单词列表的 DataFrame 转换为每个单词都在自己的行中的 DataFrame.

I would like to transform from a DataFrame that contains lists of words into a DataFrame with each word in its own row.

如何在 DataFrame 中的列上爆炸?

How do I do explode on a column in a DataFrame?

以下是我的一些尝试示例，您可以在其中取消注释每一行代码并获得以下注释中列出的错误.我在 Python 2.7 和 Spark 1.6.1 中使用 PySpark.

Here is an example with some of my attempts where you can uncomment each code line and get the error listed in the following comment. I use PySpark in Python 2.7 with Spark 1.6.1.

from pyspark.sql.functions import split, explode
DF = sqlContext.createDataFrame([('cat \n\n elephant rat \n rat cat', )], ['word'])
print 'Dataset:'
DF.show()
print '\n\n Trying to do explode: \n'
DFsplit_explode = (
 DF
 .select(split(DF['word'], ' '))
#  .select(explode(DF['word']))  # AnalysisException: u"cannot resolve 'explode(word)' due to data type mismatch: input to function explode should be array or map type, not StringType;"
#   .map(explode)  # AttributeError: 'PipelinedRDD' object has no attribute 'show'
#   .explode()  # AttributeError: 'DataFrame' object has no attribute 'explode'
).show()

# Trying without split
print '\n\n Only explode: \n'

DFsplit_explode = (
 DF 
 .select(explode(DF['word']))  # AnalysisException: u"cannot resolve 'explode(word)' due to data type mismatch: input to function explode should be array or map type, not StringType;"
).show()

请指教

推荐答案

explode 和 split 是 SQL 函数.两者都对 SQL Column 进行操作.split 将 Java 正则表达式作为第二个参数.如果你想在任意空白处分离数据，你需要这样的东西:

explode and split are SQL functions. Both operate on SQL Column. split takes a Java regular expression as a second argument. If you want to separate data on arbitrary whitespace you'll need something like this:

df = sqlContext.createDataFrame(
    [('cat \n\n elephant rat \n rat cat', )], ['word']
)

df.select(explode(split(col("word"), "\s+")).alias("word")).show()

## +--------+
## |    word|
## +--------+
## |     cat|
## |elephant|
## |     rat|
## |     rat|
## |     cat|
## +--------+

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