Mysql multiple connection problem in python

Here I have created two MySQL connections to the same database.

When one connection updates the database present in class, the other connection can't get the changes. Here is my code

tm(): Database class which handles connect, execute the query and get the overview of database

class ClassB():
    b = None

    def __init__(self):
        self.b = database()

    def get_overview_for_b(self):
        self.b.mark_invalid('9')
        self.b.mark_invalid('8')
        b_str = ''.join(map(str, self.b.get_overview()))
        print("Getting the overview of b" + b_str)


# initializing class B
inside_class_b = ClassB()
# initializing class for A
a = database()

# get database overview for A
astart = a.get_overview()
a_str = ''.join(map(str, astart))
print("Getting the overview of a before testing" + a_str)

# updating database and get database overview for B
inside_class_b.get_overview_for_b()

# get another overview for A
aend = a.get_overview()
a_str = ''.join(map(str, aend))
print("Getting the overview of a after testing" + a_str)

# The final overview of both A and B should be same, but isn't

actual output

Getting the overview of a before testing('PENDING', 2)
Getting the overview of b('INVALID', 2)
Getting the overview of a after testing('PENDING', 2)

expected output

Getting the overview of a before testing('PENDING', 2)
Getting the overview of b('INVALID', 2)
Getting the overview of a after testing('INVALID', 2)

Although I just tried, if I use 'a' to update 'b' gets the updated values.

class ClassB():
    b = None

    def __init__(self):
        self.b = database()

    def get_overview_for_b(self):
        b_str = ''.join(map(str, self.b.get_overview()))
        print("Getting the overview of b" + b_str)


# initializing class B
inside_class_b = ClassB()
# initializing class for A
a = database()

# get database overview for A
astart = a.get_overview()
a_str = ''.join(map(str, astart))
print("Getting the overview of a before testing" + a_str)

# updating using 'a'
a.mark_invalid('9')
a.mark_invalid('8')

# get database overview for B
inside_class_b.get_overview_for_b()

# get another overview for A
aend = a.get_overview()
a_str = ''.join(map(str, aend))
print("Getting the overview of a after testing" + a_str)

Expected Output and Actual output are same

Getting the overview of a before testing('PENDING', 2)
Getting the overview of b('INVALID', 2)
Getting the overview of a after testing('INVALID', 2)

EDIT The following is my execute function used by invalid. This uses a common connection that is checked for None condition everytime.

    def execute(self, statement, attributes):
        """
            Execute a query for the database
            :arg:
                statement - Statement to be executed.
                attributes - Attributes supporting the statement.
        """
        if self._db_connection is None:
            self.connect()
        cursor = self._db_connection.cursor()
        cursor.execute(statement, attributes)
        self._db_connection.commit()
        t = cursor.rowcount
        cursor.close()
        del cursor
        return t