Implemented a Database class and the call to create a Spatialite database

exposurecoquimbo/database.py

+#!/usr/bin/env python3
+
+# Copyright (C) 2021:
+#   Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum GFZ
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or (at
+# your option) any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero
+# General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program. If not, see http://www.gnu.org/licenses/.
+
+
+import logging
+import sqlite3
+
+
+# Initialize log
+logger = logging.getLogger(__name__)
+
+
+class Database:
+    """The Database class represents a Spatialite database. It manages the database
+    connection and cursor. Upon connection, the Spatialite extension is loaded.
+
+    Args:
+        database_filepath:
+            File path for the Spatialite database file.
+        spatialite_filepath:
+            File path of the Spatialite extension.
+
+    Attributes:
+        self.database_filepath (str): Spatialite database file path.
+        self.spatialite_filepath (str): File path to the Spatialite extension.
+    """
+
+    def __init__(self, database_filepath, spatialite_filepath="mod_spatialite"):
+        self.database_filepath = database_filepath
+        self.spatialite_filepath = spatialite_filepath
+
+        self.connection = None
+        self.cursor = None
+
+    def create_connection_and_cursor(self, init_spatial_metadata=True):
+        """Create a database connection, loads the Spatialite extension and initializes it.
+
+        Attributes:
+            None
+
+        Returns:
+            None
+        """
+
+        # Create SQLite database for the exposure data
+        logger.debug("Connecting to database at %s" % self.database_filepath)
+        self.connection = sqlite3.connect(self.database_filepath)
+        logger.debug("Connection to database established")
+
+        self.connection.enable_load_extension(True)
+        sql_statement = "SELECT load_extension('%s');" % self.spatialite_filepath
+        self.connection.execute(sql_statement)
+        if init_spatial_metadata:
+            self.connection.execute("SELECT InitSpatialMetaData(1);")
+            logger.debug("Spatialite extension loaded and initialized")
+
+        versions = self.connection.execute("SELECT sqlite_version(), spatialite_version()")
+        for row in versions:
+            logger.debug("SQLite version: %s" % row[0])
+            logger.debug("Spatialite version: %s" % row[1])
+
+        self.cursor = self.connection.cursor()

exposurecoquimbo/exposurecoquimbo.py

 #!/usr/bin/env python3
 
-# Copyright (c) 2020-2021:
+# Copyright (C) 2021:
 #   Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum GFZ
 #
 # This program is free software: you can redistribute it and/or modify it
@@ -16,8 +16,14 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program. If not, see http://www.gnu.org/licenses/.
 
+
 import logging
 import sys
+import argparse
+import os
+import sqlite3
+from database import Database  # pylint: disable=E0611,E0401
+
 
 # Add a logger printing error, warning, info and debug messages to the screen
 logger = logging.getLogger()
@@ -26,13 +32,48 @@ logger.addHandler(logging.StreamHandler(sys.stdout))
 
 
 def main():
+    description = "Creates the exposure model for the area of Coquimbo "
+    description += "and stores it in a Spatialite database. "
+    description += "Further options allow for output for the loss-calculator."
+    parser = argparse.ArgumentParser(description=description)
+
+    parser.add_argument("command", type=str, help="'create' to create the exposure database")
+    parser.add_argument(
+        "-d",
+        "--database",
+        required=True,
+        type=str,
+        help="File path of the database",
+    )
+    parser.add_argument(
+        "-s",
+        "--spatialite_extension",
+        required=False,
+        type=str,
+        default="mod_spatialite",
+        help="File path of the spatialite extension (default: mod_spatialite)",
+    )
+
+    args = parser.parse_args()
+
+    # Read arguments from command line
+    command = args.command
+    database_filepath = args.database
+    spatialite_filepath = args.spatialite_extension
 
-    # Example logging output
-    # This can be either logger.error(), logger.warning(), logger.info() or logger.debug()
-    logger.info("Creating exposure model of Coquimbo")
+    db = Database(database_filepath, spatialite_filepath)
 
-    # Leave the program
-    sys.exit()
+    if command == "create":
+        if os.path.exists(database_filepath):
+            logger.warning("Database exists. Exiting ...")
+            exit()
+        try:
+            db.create_connection_and_cursor()
+        except sqlite3.OperationalError:
+            logger.warning("Spatialite extension cannot be loaded. Exiting ...")
+            exit()
+    else:
+        logger.warning("Command not recognized. Exiting ...")
 
 
 if __name__ == "__main__":