Github user mateiz commented on a diff in the pull request:
https://github.com/apache/spark/pull/455#discussion_r13147714
--- Diff: python/pyspark/context.py ---
@@ -311,6 +311,98 @@ def wholeTextFiles(self, path, minPartitions=None):
return RDD(self._jsc.wholeTextFiles(path, minPartitions), self,
PairDeserializer(UTF8Deserializer(),
UTF8Deserializer()))
+ def sequenceFile(self, name, key_class="org.apache.hadoop.io.Text",
value_class="org.apache.hadoop.io.Text",
+ key_wrapper="", value_wrapper="", minSplits=None):
+ """
+ Read a Hadoop SequenceFile with arbitrary key and value Writable
class from HDFS,
+ a local file system (available on all nodes), or any
Hadoop-supported file system URI.
+ The mechanism is as follows:
+ 1. A Java RDD is created from the SequenceFile or other
InputFormat, and the key and value Writable classes
+ 2. Serialization is attempted via Pyrolite pickling
+ 3. If this fails, the fallback is to call 'toString' on each
key and value
+ 4. C{PickleSerializer} is used to deserialize pickled objects
on the Python side
+ >>> sorted(sc.sequenceFile(tempdir +
"/sftestdata/sfint/").collect())
+ [(1, u'aa'), (1, u'aa'), (2, u'aa'), (2, u'bb'), (2, u'bb'), (3,
u'cc')]
+ >>> sorted(sc.sequenceFile(tempdir +
"/sftestdata/sfdouble/").collect())
+ [(1.0, u'aa'), (1.0, u'aa'), (2.0, u'aa'), (2.0, u'bb'), (2.0,
u'bb'), (3.0, u'cc')]
+ >>> sorted(sc.sequenceFile(tempdir +
"/sftestdata/sftext/").collect())
+ [(u'1', u'aa'), (u'1', u'aa'), (u'2', u'aa'), (u'2', u'bb'),
(u'2', u'bb'), (u'3', u'cc')]
+ >>> sorted(sc.sequenceFile(tempdir +
"/sftestdata/sfbool/").collect())
+ [(1, False), (1, True), (2, False), (2, False), (2, True), (3,
True)]
+ >>> sorted(sc.sequenceFile(tempdir +
"/sftestdata/sfnull/").collect())
+ [(1, None), (1, None), (2, None), (2, None), (2, None), (3, None)]
+ >>> sorted(sc.sequenceFile(tempdir +
"/sftestdata/sfmap/").collect())
+ [(1, {2.0: u'aa'}), (1, {3.0: u'bb'}), (2, {1.0: u'aa'}), (2,
{1.0: u'cc'}), (2, {3.0: u'bb'}), (3, {2.0: u'dd'})]
+ >>> r = sorted(sc.sequenceFile(tempdir +
"/sftestdata/sfclass").collect())[0]
+ >>> r == (u'1', {u'__class__':
u'org.apache.spark.api.python.TestWritable', u'double': 54.0, u'int': 123,
u'str': u'test1'})
+ True
--- End diff --
Nit: instead of having doctests here, it would be better to put a test in
`pyspark/tests.py` for this particular case. The reason is that doctests should
ideally be self-contained and should also serve as documentation, but these
depend on some files that the reader of the docs won't know about.
Instead, maybe add `@param` statements for the arguments. Look at
`pyspark/conf.py` to see how to format these in Epydoc.
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