GitHub user HyukjinKwon opened a pull request: https://github.com/apache/spark/pull/17160
[SPARK-19701][SQL][PYTHON] Throws a correct exception for 'in' operator against column ## What changes were proposed in this pull request? This PR proposes to remove incorrect implementation that has been not executed so far (at least from Spark 1.5.2) for `in` operator and throw a correct exception rather than saying it is a bool. I tested the codes above in 1.5.2, 1.6.3, 2.1.0 and in the master branch as below: **1.5.2** ```python >>> df = sqlContext.createDataFrame([[1]]) >>> 1 in df._1 Traceback (most recent call last): File "<stdin>", line 1, in <module> File ".../spark-1.5.2-bin-hadoop2.6/python/pyspark/sql/column.py", line 418, in __nonzero__ raise ValueError("Cannot convert column into bool: please use '&' for 'and', '|' for 'or', " ValueError: Cannot convert column into bool: please use '&' for 'and', '|' for 'or', '~' for 'not' when building DataFrame boolean expressions. ``` **1.6.3** ```python >>> 1 in sqlContext.range(1).id Traceback (most recent call last): File "<stdin>", line 1, in <module> File ".../spark-1.6.3-bin-hadoop2.6/python/pyspark/sql/column.py", line 447, in __nonzero__ raise ValueError("Cannot convert column into bool: please use '&' for 'and', '|' for 'or', " ValueError: Cannot convert column into bool: please use '&' for 'and', '|' for 'or', '~' for 'not' when building DataFrame boolean expressions. ``` **2.1.0** ```python >>> 1 in spark.range(1).id Traceback (most recent call last): File "<stdin>", line 1, in <module> File ".../spark-2.1.0-bin-hadoop2.7/python/pyspark/sql/column.py", line 426, in __nonzero__ raise ValueError("Cannot convert column into bool: please use '&' for 'and', '|' for 'or', " ValueError: Cannot convert column into bool: please use '&' for 'and', '|' for 'or', '~' for 'not' when building DataFrame boolean expressions. ``` **Current Master** ```python >>> 1 in spark.range(1).id Traceback (most recent call last): File "<stdin>", line 1, in <module> File ".../spark/python/pyspark/sql/column.py", line 452, in __nonzero__ raise ValueError("Cannot convert column into bool: please use '&' for 'and', '|' for 'or', " ValueError: Cannot convert column into bool: please use '&' for 'and', '|' for 'or', '~' for 'not' when building DataFrame boolean expressions. ``` **After** ```python >>> 1 in spark.range(1).id Traceback (most recent call last): File "<stdin>", line 1, in <module> File ".../spark/python/pyspark/sql/column.py", line 184, in __contains__ raise ValueError("Cannot apply 'in' operator against a column: please use 'contains' " ValueError: Cannot apply 'in' operator against a column: please use 'contains' in a string column or 'array_contains' function for an array column. ``` In more details, It seems the implementation indented to support this ```python 1 in df.column ``` However, currently, it throws an exception as below: ```python Traceback (most recent call last): File "<stdin>", line 1, in <module> File ".../spark/python/pyspark/sql/column.py", line 426, in __nonzero__ raise ValueError("Cannot convert column into bool: please use '&' for 'and', '|' for 'or', " ValueError: Cannot convert column into bool: please use '&' for 'and', '|' for 'or', '~' for 'not' when building DataFrame boolean expressions. ``` What happens here is as below: ```python class Column(object): def __contains__(self, item): print "I am contains" return Column() def __nonzero__(self): raise Exception("I am nonzero.") >>> 1 in Column() I am contains Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 6, in __nonzero__ Exception: I am nonzero. ``` It seems it calls `__contains__` first and then `__nonzero__` or `__bool__` is being called against `Column()` to make this a bool (or int to be specific). It seems `__nonzero__` (for Python 2), `__bool__` (for Python 3) and `__contains__` forcing the the return into a bool unlike other operators. There are few references about this as below: http://stackoverflow.com/questions/12244074/python-source-code-for-built-in-in-operator/12244378#12244378 http://stackoverflow.com/questions/38542543/functionality-of-python-in-vs-contains/38542777 It seems we can't overwrite `__nonzero__` or `__bool__` as a workaround to make this working because these force the return type as a bool as below: ```python class Column(object): def __contains__(self, item): print "I am contains" return Column() def __nonzero__(self): return "a" >>> 1 in Column() I am contains Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: __nonzero__ should return bool or int, returned str ``` ## How was this patch tested? Added unit tests in `tests.py`. You can merge this pull request into a Git repository by running: $ git pull https://github.com/HyukjinKwon/spark SPARK-19701 Alternatively you can review and apply these changes as the patch at: https://github.com/apache/spark/pull/17160.patch To close this pull request, make a commit to your master/trunk branch with (at least) the following in the commit message: This closes #17160 ---- commit 509747ca82aecd07541cc5b0c06fd5f4c147c3cf Author: hyukjinkwon <gurwls...@gmail.com> Date: 2017-03-04T03:37:48Z Throws a correct exception for in operator against column ---- --- If your project is set up for it, you can reply to this email and have your reply appear on GitHub as well. 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