Details
Critical Description
Currently, PySpark does not work with Python 3.6.0.
Running ./bin/pyspark simply throws the error as below:
Traceback (most recent call last): File ".../spark/python/pyspark/shell.py", line 30, in <module> import pyspark File ".../spark/python/pyspark/__init__.py", line 46, in <module> from pyspark.context import SparkContext File ".../spark/python/pyspark/context.py", line 36, in <module> from pyspark.java_gateway import launch_gateway File ".../spark/python/pyspark/java_gateway.py", line 31, in <module> from py4j.java_gateway import java_import, JavaGateway, GatewayClient File "<frozen importlib._bootstrap>", line 961, in _find_and_load File "<frozen importlib._bootstrap>", line 950, in _find_and_load_unlocked File "<frozen importlib._bootstrap>", line 646, in _load_unlocked File "<frozen importlib._bootstrap>", line 616, in _load_backward_compatible File ".../spark/python/lib/py4j-0.10.4-src.zip/py4j/java_gateway.py", line 18, in <module> File "/usr/local/Cellar/python3/3.6.0/Frameworks/Python.framework/Versions/3.6/lib/python3.6/pydoc.py", line 62, in <module> import pkgutil File "/usr/local/Cellar/python3/3.6.0/Frameworks/Python.framework/Versions/3.6/lib/python3.6/pkgutil.py", line 22, in <module> ModuleInfo = namedtuple('ModuleInfo', 'module_finder name ispkg') File ".../spark/python/pyspark/serializers.py", line 394, in namedtuple cls = _old_namedtuple(*args, **kwargs) TypeError: namedtuple() missing 3 required keyword-only arguments: 'verbose', 'rename', and 'module'
The problem is in https://github.com/apache/spark/blob/3c68944b229aaaeeaee3efcbae3e3be9a2914855/python/pyspark/serializers.py#L386-L394 as the error says and the cause seems because the arguments of namedtuple are now completely keyword-only arguments from Python 3.6.0 (See https://bugs.python.org/issue25628).
We currently copy this function via types.FunctionType which does not set the default values of keyword-only arguments (meaning namedtuple._kwdefaults_) and this seems causing internally missing values in the function (non-bound arguments).
This ends up as below:
import types import collections def _copy_func(f): return types.FunctionType(f.__code__, f.__globals__, f.__name__, f.__defaults__, f.__closure__) _old_namedtuple = _copy_func(collections.namedtuple) _old_namedtuple(, "b") _old_namedtuple("a")
If we call as below:
>>> _old_namedtuple("a", "b") Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: namedtuple() missing 3 required keyword-only arguments: 'verbose', 'rename', and 'module'
It throws an exception as above becuase _kwdefaults_ for required keyword arguments seem unset in the copied function. So, if we give explicit value for these,
>>> _old_namedtuple("a", "b", verbose=False, rename=False, module=None) <class '__main__.a'>
It works fine.
It seems now we should properly set these into the hijected one.
