text: #
  # Copyright 2016 The BigDL Authors.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  #
  
  import sys
  import os
  import glob
  
  def __prepare_spark_env():
      modules = sys.modules
      if "pyspark" not in modules or "py4j" not in modules:
          spark_home = os.environ.get('SPARK_HOME', None)
          if not spark_home:
              raise ValueError(
                  """Could not find Spark. Pls make sure SPARK_HOME env is set:
                     export SPARK_HOME=path to your spark home directory""")
          print("Using %s" % spark_home)
          py4j = glob.glob(os.path.join(spark_home, 'python/lib', 'py4j-*.zip'))[0]
          pyspark = glob.glob(os.path.join(spark_home, 'python/lib', 'pyspark*.zip'))[0]
          sys.path.insert(0, py4j)
          sys.path.insert(0, pyspark)
  
  
  def __prepare_bigdl_env():
      jar_dir = os.path.abspath(__file__ + "/../../")
      jar_paths = glob.glob(os.path.join(jar_dir, "share/lib/*.jar"))
      conf_paths = glob.glob(os.path.join(jar_dir, "share/conf/*.conf"))
  
      def append_path(env_var_name, path):
          try:
              print("Adding %s to %s" % (jar_paths[0], env_var_name))
              os.environ[env_var_name] = path + ":" + os.environ[
                  env_var_name]  # noqa
          except KeyError:
              os.environ[env_var_name] = path
  
      if conf_paths and conf_paths:
          assert len(conf_paths) == 1, "Expecting one jar: %s" % len(jar_paths)
          assert len(conf_paths) == 1, "Expecting one conf: %s" % len(conf_paths)
          append_path("SPARK_CLASSPATH", jar_paths[0])
          print("Prepending %s to sys.path" % conf_paths[0])
          sys.path.insert(0, conf_paths[0])
  
  
  def prepare_env():
      __prepare_spark_env()
      __prepare_bigdl_env()