def select_and_update():
""""
show how we can select a specific record, and then search and read through several records
"""
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)
database = SqliteDatabase('../data/personjob.db')
try:
database.connect()
database.execute_sql('PRAGMA foreign_keys = ON;')
logger.info('Find and display by selecting a spcific Person name...')
# Peewee provides us with the get() method
aperson = Person.get(Person.person_name == 'Susan')
logger.info(f'{aperson.person_name} lives in {aperson.lives_in_town} ' + \
f' and likes to be known as {aperson.nickname}')
logger.info('Search and display all Person with missing nicknames')
logger.info(
'Our person class inherits select(). Specify search with .where()')
logger.info('Peter gets a nickname but noone else')
# We also get a select() and where() method that we can use
for person in Person.select().where(Person.nickname is None):
logger.info(
f'{person.person_name} does not have a nickname; see: {person.nickname}'
)
if person.person_name == 'Peter':
logger.info('Changing nickname for Peter')
logger.info('Update the database')
person.nickname = 'Painter'
person.save()
else:
logger.info(f'Not giving a nickname to {person.person_name}')
logger.info(
'And here is where we prove it by finding Peter and displaying')
aperson = Person.get(Person.person_name == 'Peter')
logger.info(
f'{aperson.person_name} now has a nickname of {aperson.nickname}')
except Exception as e:
logger.info(e)
finally:
database.close()
def cant_change_pk():
"""
show that PKs cant be changed (and that there is no error!)
"""
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)
logger.info("Back to Person class: try to change Peter's name")
aperson = Person.get(Person.person_name == 'Peter')
logger.info(f'Current value is {aperson.person_name}')
logger.info('Update Peter to Peta, thereby trying to change the PK...')
database = SqliteDatabase('../data/personjob.db')
try:
try:
with database.transaction():
aperson = Person.get(Person.person_name == 'Peter')
aperson.person_name = 'Peta'
aperson.save()
logger.info(f'Tried to change Peter to {aperson.person_name}')
except Exception as e:
logger.info(f'Cant change a PK and caught you trying'
) # not caught; no error thrown by Peewee
logger.info(e)
aperson = Person.get(Person.person_name == 'Peter')
logger.info(f'Looked for Peter: found! -> {aperson.person_name}')
try:
aperson = Person.get(Person.person_name == 'Peta')
except Exception as e:
logger.info(
f'Looking for Peta results in zero records. PK changes are ignored and do not throw an '
f'error!!!!')
logger.info(f'Cant change a PK')
logger.info(
'PK "change" can only be achieved with a delete and new create'
)
finally:
database.close()
def join_classes():
"""
demonstrate how to join classes together : no matches too
"""
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)
database = SqliteDatabase('../data/personjob.db')
logger.info(
'View matching records and Persons without Jobs (note LEFT_OUTER)')
try:
database.connect()
database.execute_sql('PRAGMA foreign_keys = ON;')
query = (Person.select(Person, Job).join(Job, JOIN.LEFT_OUTER))
for person in query:
try:
logger.info(
f'Person {person.person_name} had job {person.job.job_name}'
)
except Exception as e:
logger.info(f'Person {person.person_name} had no job')
logger.info('Example of how to summarize data')
logger.info('Note select() creates a count and names it job_count')
logger.info('group_by and order_by control level and sorting')
query = (Person.select(Person,
fn.COUNT(Job.job_name).alias('job_count')).join(
Job,
JOIN.LEFT_OUTER).group_by(Person).order_by(
Person.person_name))
for person in query:
logger.info(f'{person.person_name} had {person.job_count} jobs')
except Exception as e:
logger.info(e)
finally:
database.close()
def add_and_delete():
""""
show how we can add a record, and delete a record
"""
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)
database = SqliteDatabase('../data/personjob.db')
try:
database.connect()
database.execute_sql('PRAGMA foreign_keys = ON;')
logger.info('Add and display a Person called Fred; then delete him...')
logger.info('Add Fred in one step')
new_person = Person.create(person_name='Fred',
lives_in_town='Seattle',
nickname='Fearless')
new_person.save()
logger.info('Show Fred')
aperson = Person.get(Person.person_name == 'Fred')
logger.info(
f'We just created {aperson.person_name}, who lives in {aperson.lives_in_town}'
)
logger.info('but now we will delete him...')
aperson.delete_instance()
logger.info(
'Reading and print all Person records (but not Fred; he has been deleted)...'
)
for person in Person:
logger.info(
f"{person.person_name} lives in {person.lives_in_town} and likes to be known as {person.nickname}"
)
except Exception as e:
logger.info(e)
finally:
database.close()
def populate_db():
"""
add person data to database
"""
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)
database = SqliteDatabase('../data/personjob.db')
logger.info('Working with Person class')
logger.info(
'Note how I use constants and a list of tuples as a simple schema')
logger.info(
'Normally you probably will have prompted for this from a user')
person_name = 0
lives_in_town = 1
nickname = 2
people = [
('Andrew', 'Sumner', 'Andy'),
('Peter', 'Seattle', None),
('Susan', 'Boston', 'Beannie'),
('Pam', 'Coventry', 'PJ'),
('Steven', 'Colchester', None),
]
logger.info('Creating Person records: iterate through the list of tuples')
logger.info('Prepare to explain any errors with exceptions')
logger.info('and the transaction tells the database to fail on error')
try:
database.connect()
database.execute_sql('PRAGMA foreign_keys = ON;')
for person in people:
with database.transaction():
new_person = Person.create(person_name=person[person_name],
lives_in_town=person[lives_in_town],
nickname=person[nickname])
new_person.save()
logger.info('Database add successful')
logger.info('Print the Person records we saved...')
for saved_person in Person:
logger.info(f'{saved_person.person_name} lives in {saved_person.lives_in_town} ' + \
f'and likes to be known as {saved_person.nickname}')
except Exception as e:
logger.info(f'Error creating = {person[person_name]}')
logger.info(e)
logger.info('See how the database protects our data')
finally:
logger.info('database closes')
database.close()
def join_classes():
"""
demonstrate how to join classes together : matches
"""
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)
database = SqliteDatabase('personjob.db')
logger.info('Working with Job class')
logger.info(
'Now resolve the join and print (INNER shows only jobs that match person)...'
)
logger.info('Notice how we use a query variable in this case')
logger.info('We select the classes we need, and we join Person to Job')
logger.info(
'Inner join (which is the default) shows only records that match')
try:
database.connect()
database.execute_sql('PRAGMA foreign_keys = ON;')
query = (Person.select(
Person, Job, Department).join(Job).switch(Person).join(Department))
logger.info('View matching records from both tables')
for person in query:
logger.info(
f'Person {person.person_name} had job {person.job.job_name} in the {person.department.department_name} department '
)
except Exception as e:
logger.info(f'Error creating = {job[JOB_NAME]}')
logger.info(e)
finally:
logger.info('database closes')
database.close()
def add_with_without_bk():
"""
demonstrate impact of business keys
"""
person_name = 0
lives_in_town = 1
nickname = 2
people = [
('Andrew', 'Sumner', 'Andy'),
('Peter', 'Seattle', None),
('Susan', 'Boston', 'Beannie'),
('Pam', 'Coventry', 'PJ'),
('Steven', 'Colchester', None),
]
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)
database = SqliteDatabase('../data/personjob.db')
logger.info('Try creating Person records again: it will fail')
try:
database.connect()
database.execute_sql('PRAGMA foreign_keys = ON;')
try:
with database.transaction():
for person in people:
new_person = Person.create(
person_name=person[person_name],
lives_in_town=person[lives_in_town],
nickname=person[nickname])
new_person.save()
logger.info('Database add successful')
except Exception as e:
logger.info(f'Error creating = {person[person_name]}')
logger.info(e)
logger.info(
'We make sure duplicates are not unintentionally created this way')
logger.info('BUT: how do we really identify a Person (uniquely)?')
logger.info(
'Creating Person records, but in a new table with generated PK...')
try:
with database.transaction():
for person in people:
new_person = PersonNumKey.create(
person_name=person[person_name],
lives_in_town=person[lives_in_town],
nickname=person[nickname])
new_person.save()
except Exception as e:
logger.info(f'Error creating = {person[0]}')
logger.info(e)
logger.info('Watch what happens when we do it again')
try:
with database.transaction():
for person in people:
new_person = PersonNumKey.create(
person_name=person[person_name],
lives_in_town=person[lives_in_town],
nickname=person[nickname])
new_person.save()
except Exception as e:
logger.info(f'Error creating = {person[0]}')
logger.info(e)
logger.info(
'Note no PK specified, no PK violation; "duplicates" created!')
for person in PersonNumKey.select():
logger.info(f'Name : {person.person_name} with id: {person.id}')
except Exception as e:
logger.info(e)
finally:
database.close()