Cover spark_singleton.py

Author: ghanse

dbldatagen/spark_singleton.py

@@ -9,35 +9,39 @@
 for use cases like unit testing rather than in a Databricks workspace environment
 """
 
-import os
 import logging
+import os
+
 from pyspark.sql import SparkSession
 
 
 class SparkSingleton:
     """A singleton class which returns one Spark session instance"""
 
     @classmethod
-    def getInstance(cls):
-        """Create a Spark instance for Datalib.
+    def getInstance(cls) -> SparkSession:
+        """Creates a `SparkSession` instance for Datalib.
 
         :returns: A Spark instance
         """
 
         return SparkSession.builder.getOrCreate()
 
     @classmethod
-    def getLocalInstance(cls, appName="new Spark session", useAllCores=True):
-        """Create a machine local Spark instance for Datalib.
+    def getLocalInstance(cls, appName: str = "new Spark session", useAllCores: bool = True) -> SparkSession:
+        """Creates a machine local `SparkSession` instance for Datalib.
         By default, it uses `n-1` cores  of the available cores for the spark session,
         where `n` is total cores available.
 
+        :param appName: Name to use for the local `SparkSession` instance
         :param useAllCores:  If `useAllCores` is True, then use all cores rather than `n-1` cores
-        :returns: A Spark instance
+        :returns: A `SparkSession` instance
         """
         cpu_count = os.cpu_count()
 
-        if useAllCores:
+        if not cpu_count:
+            spark_core_count = 1
+        elif useAllCores:
             spark_core_count = cpu_count
         else:
             spark_core_count = cpu_count - 1

pyproject.toml

@@ -164,7 +164,6 @@ exclude = [
     "dbldatagen/nrange.py",
     "dbldatagen/schema_parser.py",
     "dbldatagen/serialization.py",
-    "dbldatagen/spark_singleton.py",
     "dbldatagen/text_generator_plugins.py",
     "dbldatagen/text_generators.py",
     "dbldatagen/utils.py"
@@ -250,7 +249,6 @@ ignore = [
     "dbldatagen/nrange.py",
     "dbldatagen/schema_parser.py",
     "dbldatagen/serialization.py",
-    "dbldatagen/spark_singleton.py",
     "dbldatagen/text_generator_plugins.py",
     "dbldatagen/text_generators.py",
     "dbldatagen/utils.py"
@@ -291,7 +289,6 @@ ignore-paths = [
     "dbldatagen/nrange.py",
     "dbldatagen/schema_parser.py",
     "dbldatagen/serialization.py",
-    "dbldatagen/spark_singleton.py",
     "dbldatagen/text_generator_plugins.py",
     "dbldatagen/text_generators.py",
     "dbldatagen/utils.py"
@@ -427,7 +424,6 @@ exclude = [
     "dbldatagen/nrange.py",
     "dbldatagen/schema_parser.py",
     "dbldatagen/serialization.py",
-    "dbldatagen/spark_singleton.py",
     "dbldatagen/text_generator_plugins.py",
     "dbldatagen/text_generators.py",
     "dbldatagen/utils.py"