python_cassandra_simple_app.md

create a file python_cass_lab.py with the following code

import logging from cassandra import ConsistencyLevel from cassandra.cluster import Cluster, BatchStatement from cassandra.query import SimpleStatement

class PythonCassandraExample:

  def __init__(self):
      self.cluster = None
      self.session = None
      self.keyspace = None
      self.log = None

  def __del__(self):
      self.cluster.shutdown()

  #connect to cluster
  def createsession(self):
      self.cluster = Cluster(['localhost'])
      self.session = self.cluster.connect(self.keyspace)

  def getsession(self):
      return self.session

  # Add some log info
  def setlogger(self):
      log = logging.getLogger()
      log.setLevel('INFO')
      handler = logging.StreamHandler()
      handler.setFormatter(logging.Formatter("%(asctime)s [%(levelname)s] %(name)s: %(message)s"))
      log.addHandler(handler)
      self.log = log

  # Create Keyspace based on Given Name
  def createkeyspace(self, keyspace):

      # Create new keyspace
      rows = self.session.execute("SELECT keyspace_name FROM system_schema.keyspaces")
      if keyspace in [row[0] for row in rows]:
          self.log.info("dropping existing keyspace...")
          self.session.execute("DROP KEYSPACE " + keyspace)

      self.log.info("creating keyspace...")
      self.session.execute("""
              CREATE KEYSPACE %s
              WITH replication = { 'class': 'SimpleStrategy', 'replication_factor': '2' }
              """ % keyspace)

      self.log.info("setting keyspace...")
      self.session.set_keyspace(keyspace)

  def create_table(self):
      c_sql = """
              CREATE TABLE IF NOT EXISTS students (st_id int PRIMARY KEY,
                                            name varchar,
                                            age int ,
                                            city varchar);
               """
      self.session.execute(c_sql)
      self.log.info("Students Table Created !!!")

  # lets do some batch insert
  def insert_data(self):
      insert_sql = self.session.prepare("INSERT INTO  students (st_id, name , age,city) VALUES (?,?,?,?)")
      batch = BatchStatement()
      batch.add(insert_sql, (1, 'Shaun', 38, 'Austin'))
      batch.add(insert_sql, (2, 'Meghan', 34, 'Toronto'))
      batch.add(insert_sql, (3, 'Jamal', 24, 'Chicago'))
      batch.add(insert_sql, (4, 'Mohamed', 32, 'San Francisco'))
      self.session.execute(batch)
      self.log.info('Batch Insert Completed')

  def select_data(self):
      rows = self.session.execute('select * from students limit 4;')
      for row in rows:
          print(row.name, row.city)

  def update_data(self):
      pass

  def delete_data(self):
      pass

if name == 'main': example1 = PythonCassandraExample() example1.createsession() example1.setlogger() example1.createkeyspace('cass_py_lab') example1.create_table() example1.insert_data() example1.select_data()

Run the python file in your terminal

python python_cass_lab.py

You should see something like this result

2019-01-10 17:28:49,778 [INFO] root: dropping existing keyspace...

2019-01-10 17:28:51,195 [INFO] root: creating keyspace...

2019-01-10 17:28:51,875 [INFO] root: setting keyspace...

2019-01-10 17:28:52,510 [INFO] root: Students Table Created !!!

2019-01-10 17:28:52,540 [INFO] root: Batch Insert Completed

(u'Shaun', u'Austin')

(u'Meghan', u'Toronto')

(u'Mohamed', u'San Francisco')

(u'Jamal', u'Chicago')

Try to edit the code for the below scenario

1. Create a new table called "classes" and
2. Create columns that represent the class name, max enrollment, campus, teacher, course number
3. Choose a Primary Key
4. Add 5 entrys to those tables. Assume there are two compuses North and South.
5. Query the table and return classes on South campus.
6. Print class and teacher to screen.

Run your Python Program and View Your Results