[Python] Database Class

import sys
try:
    import MySQLdb
except ImportError:
    print("Please install MySQL-python!")
    sys.exit()

class database:
    hostname = ''
    username = ''
    password = ''
    database = ''
    db = None
    q = None
    cur = None
    def __init__(self):
        self.connect()

    def __del__(self):
        self.disconnect()

    def connect(self):
        self.db = MySQLdb.connect(host=self.hostname, user=self.username, passwd=self.password, db=self.database)
        self.cur = self.db.cursor()


    def disconnect(self):
        if self.cur != None:
            self.cur.close()
        if self.db != None:
            self.db.close()

    def query(self, query=''):
        self.cur.close()
        self.cur = self.db.cursor()
        self.q = self.cur.execute(query)
        return self.q

    def countRows(self, table='', what='*'):
        q = self.query("SELECT COUNT('+what+') FROM `"+table+"`;")
        return int(self.cur.fetchone()[0])

    def escape(self, string):
        self.cur.close()
        return MySQLdb.escape_string(string)

    def insert(self, table='', data={}):
        keys = []
        values = []
        for key,value in enumerate(data):
            del data[key]
            value = self.escape(value)
            if is_numeric(value):
                keys.append('`'+key+'`')
                values.append(str(value))
            else:
                keys.append('`'+key+'`')
                values.append('"'+str(value)+'"')
        self.query('INSERT INTO '+table+' ('+(','.join(keys))+') VALUES ('+(','.join(values))+');')

    def select(self, what='*', table='', where=None, start=None, max=None, returnAll=False):
        if where != None:
            where = 'WHERE '+where
        else:
            where = ''

        limit = ''
        if start != None and max == None:
            raise Exception('Cannot have a start value but no max value!')
        elif self.is_numeric(max):
            if start == None:
                start = '0'
            limit = 'LIMIT '+start+','+str(max)
        return self.fetch('SELECT '+what+' FROM '+table+' '+where+' '+limit+';', returnAll)

    def fetch(self, query='', returnAll=False):
        c = self.query(query)
        desc = self.cur.description
        rows = []
        for i in self.cur.description:
            rows.append(i[0])
        if(returnAll):
            Return = []
            for row in self.cur.fetchall():
                if row == None:
                    break
                t = {}
                for index,value in enumerate(row):
                    if self.is_numeric(value):
                        t[rows[index]] = int(value)
                    else:
                        t[rows[index]] = str(value)
                Return.append(t)
            return Return
        else:
            row = self.cur.fetchone()
            t = {}
            for index,value in enumerate(row):
                if self.is_numeric(value):
                    t[rows[index]] = int(value)
                else:
                    t[rows[index]] = str(value)
            return t

    def delete(self, table, where='', limit=1):
        if where != '':
            where = 'WHERE '+where
        if not self.is_numeric(limit):
            limit = ''
        else:
            limit = 'LIMIT '+str(limit)
        return self.query('DELETE FROM '+table+' '+where+' '+limit+';')

    def is_numeric(self, var):
        try:
            float(str(var))
            return True
        except Exception:
            return False