Create kml_to_sqlite.py

This python program requires at least python 3.0. The KML file should be in the same folder as this program by default. The SQLite database will also be created in this folder by default.# Brandt Newton
# Barre Forest Guide Database Builder
# 10/27/2014

from xml.dom import minidom
import sqlite3


# Global Variables

# Filenames & paths
kml_directory = ''
kml_file = 'MillstoneTrails.kml'

db_directoy = ''
db_file = 'bfg.sqlite'

# KML
kmldoc = minidom.parse(kml_directory + kml_file)

# SQLite Database connection
connection = sqlite3.connect(db_directoy + db_file)
cursor = connection.cursor()


# Main() proesses the information for each placemarker in the KML file and 
# inserts it into the database. Processing and insertion happens every
# iteration of the primary for loop.
def main():
	# Used to count the number of unique tags processed.
	tag_counter = 0

	# Used to count number of trails added
	placemark_counter = 0

	# Drop & create tables
	drop_tables()
	create_tables()


	# Begin processing placemarkers in KML file.

	kml = kmldoc.getElementsByTagName('kml')[0]
	document = kml.getElementsByTagName('Document')[0]
	placemarks = document.getElementsByTagName('Placemark')

	print("Processing placemarkers...", end="")
	for placemark in placemarks:
		# Get names, tags & distance
		extended_data = placemark.getElementsByTagName('ExtendedData')[0]
		data = extended_data.getElementsByTagName('SchemaData')[0].childNodes

		summer_tag = data[1].firstChild.nodeValue 			# Summer tag
		winter_tag = data[3].firstChild.nodeValue 			# Winter tag
		summer_name = data[7].firstChild.nodeValue 			# Summer name
		winter_name = data[9].firstChild.nodeValue 			# Winter name
		distance = float(data[21].firstChild.nodeValue) 	# Distance (meters)

		# Get coordinates
		lineString = document.getElementsByTagName('LineString')[0]
		coordinate_string = lineString.getElementsByTagName('coordinates')[0].firstChild.nodeValue

		coordinates = coordinate_string.split(',')

		coordinate_counter = 0

		for coordinate in coordinates:
			if coordinate[:2] =='0 ':
				coordinate = coordinate[2:]

			try:
				float_coordinate = float(coordinate)

			except ValueError:
				# Coordinate is some String
				print("Invalid coordinate:", coordinate, ". Placemark:", placemark_counter, ".")

			else:
				# Coordinate is valid
				if float_coordinate != 0:
					coordinates[coordinate_counter] = float_coordinate
					coordinate_counter += 1

		# Insert trails information
		trail_values = [placemark_counter, summer_name, winter_name, distance]
		cursor.execute("""INSERT INTO trails VALUES(?, ?, ?, ?)""", trail_values)

		# Insert trail tags & tag-trail relationship
		tag_counter = add_tag(summer_tag, placemark_counter, tag_counter)

		if summer_tag != winter_tag:
			tag_counter = add_tag(winter_tag, placemark_counter, tag_counter)
		
		# Insert trail coordinates
		for i in range(0, int(len(coordinates)/2)):
			lattitude = coordinates[i*2]
			longitude = coordinates[i*2 +1]

			coordinate_values = [placemark_counter, lattitude, longitude]

			cursor.execute("""INSERT INTO coordinates VALUES(?, ?, ?)""", coordinate_values)

		connection.commit()

		placemark_counter += 1

	print("Done.")
	# Close connection
	cursor.close()

# Checks to see if tag has already been stored. If this is a new tag it is stored.
# The trail-tag relationship is then added. The tag_counter is returned in case
# it was updated.
def add_tag(tag, trail_id, tag_counter):
	
	cursor.execute("""SELECT id FROM trail_tags WHERE tag LIKE ? """, (tag,))
	selected_tag = cursor.fetchone()


	if selected_tag == None:
		tag_id = tag_counter

		# Store new tag
		tag_values = [tag_id, tag]
		cursor.execute("""INSERT INTO trail_tags VALUES(?, ?)""", tag_values)

		tag_counter += 1

	else:
		# Get tag_id of previously stored tag
		tag_id = int(selected_tag[0])

	# Add tag-trail relationship
	trail_tag_values = [trail_id, tag_id]
	cursor.execute("""INSERT INTO trail_tag_ids VALUES(?, ?)""", trail_tag_values)

	# Update global non-local tag_counter
	return tag_counter


def drop_tables():
	print("Dropping tables...", end="")
	cursor.execute("""DROP TABLE IF EXISTS trails""")
	cursor.execute("""DROP TABLE IF EXISTS trail_tag_ids""")
	cursor.execute("""DROP TABLE IF EXISTS trail_tags""")
	cursor.execute("""DROP TABLE IF EXISTS coordinates""")
	print("Done.")

def create_tables():
	print("Creating tables...", end="")

	# The trails table is used to store each unique trail or sub trail
	cursor.execute("""CREATE TABLE trails (
					id				INTEGER PRIMARY KEY,
					name_summer		TEXT,
					name_winter		TEXT,
					distance		REAL

					)""")

	# Trail-tag tag many-to-many relationship table. This allows for
	# trails to have any number of tags.
	cursor.execute("""CREATE TABLE trail_tag_ids (
					trail_id 	INTEGER,
					tag_id 		INTEGER,
					FOREIGN KEY(trail_id) REFERENCES trails(id),
					FOREIGN KEY(tag_id) REFERENCES trail_tags(id)

					)""")

	# The trail_tags table lists all unique trail tags and is referenced
	# by the the trail_tag_ids table.
	cursor.execute("""CREATE TABLE trail_tags (
					id 		INTEGER	PRIMARY KEY,
	    			tag 	TEXT
					
					)""")

	# The coordinates table stores all coordinates for the trails.
	cursor.execute("""CREATE TABLE coordinates (
					trail_id 	INTEGER,
					lattitude 	REAL,
					longitude	REAL,
					FOREIGN KEY(trail_id) REFERENCES trails(id)

					)""")

	connection.commit()
	print("Done.")

main()