Explode in PySpark

问题:

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

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

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() 

Please advice

回答1:

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| ## +--------+ 

回答2:

To split on whitespace and also remove blank lines, add the where clause.

DF = sqlContext.createDataFrame([('cat \n\n elephant rat \n rat cat\nmat\n', )], ['word'])  >>> (DF.select(explode(split(DF.word, "\s")).alias("word"))        .where('word != ""')        .show())  +--------+ |    word| +--------+ |     cat| |elephant| |     rat| |     rat| |     cat| |     mat| +--------+ 

文章来源: Explode in PySpark