API Reference

Expressions

Peewee was designed to provide a simple, expressive, and pythonic way of executing queries. This section will provide a quick overview of some common types of expressions.

There are two primary types of objects that can be composed to create expressions:

  • Field instances
  • SQL aggregations and functions using fn

We will assume a simple “User” model with fields for username and other things. It looks like this:

class User(Model):
    username = CharField()
    is_admin = BooleanField()
    is_active = BooleanField()
    last_login = DateTimeField()
    login_count = IntegerField()
    failed_logins = IntegerField()

Comparisons use the Column lookups:

# username is equal to 'charlie'
User.username == 'charlie'

# user has logged in less than 5 times
User.login_count < 5

Comparisons can be combined using bitwise “and” and “or”. Operator precedence is controlled by python and comparisons can be nested to an arbitrary depth:

# user is both and admin and has logged in today
(User.is_admin == True) & (User.last_login >= today)

# user's username is either charlie or charles
(User.username == 'charlie') | (User.username == 'charles')

Comparisons can be used with functions as well:

# user's username starts with a 'g' or a 'G':
fn.Lower(fn.Substr(User.username, 1, 1)) == 'g'

We can do some fairly interesting things, as expressions can be compared against other expressions. Expressions also support arithmetic operations:

# users who entered the incorrect more than half the time and have logged
# in at least 10 times
(User.failed_logins > (User.login_count * .5)) & (User.login_count > 10)

Expressions allow us to do atomic updates:

# when a user logs in we want to increment their login count:
User.update(login_count=User.login_count + 1).where(User.id == user_id)

Expressions can be used in all parts of a query, so experiment!

Models

class Model(**kwargs)

Models provide a 1-to-1 mapping to database tables. Subclasses of Model declare any number of Field instances as class attributes. These fields correspond to columns on the table.

Table-level operations, such as select/update/insert/delete queries, are implemented as classmethods. Row-level operations such as saving or deleting individual instances are implemented as instancemethods.

Parameters:kwargs – Initialize the model, assigning the given key/values to the appropriate fields.

Example:

class User(Model):
    username = CharField()
    join_date = DateTimeField()
    is_admin = BooleanField()

u = User(username='charlie', is_admin=True)
classmethod select(*selection)
Parameters:selection – a list of model classes, field instances, functions or expressions
Return type:a SelectQuery for the given Model

Examples of selecting all columns (default):

User.select().where(User.active == True).order_by(User.username)

Example of selecting all columns on Tweet and the parent model, User. When the user foreign key is accessed on a Tweet instance no additional query will be needed:

(Tweet
  .select(Tweet, User)
  .join(User)
  .order_by(Tweet.created_date.desc()))
classmethod update(**update)
Parameters:update – mapping of field-name to expression
Return type:an UpdateQuery for the given Model

Example showing users being marked inactive if their registration expired:

q = User.update(active=False).where(User.registration_expired == True)
q.execute()  # execute the query, updating the database.

Example showing an atomic update:

q = PageView.update(count=PageView.count + 1).where(PageView.url == url)
q.execute()  # execute the query, updating the database.
classmethod insert(**insert)
Parameters:insert – mapping of field-name to expression
Return type:an InsertQuery for the given Model

Example showing creation of a new user:

q = User.insert(username='admin', active=True, registration_expired=False)
q.execute()  # perform the insert.
classmethod delete()
Return type:a DeleteQuery for the given Model

Example showing the deletion of all inactive users:

q = User.delete().where(User.active == False)
q.execute()  # remove the rows

Warning

This method performs a delete on the entire table. To delete a single instance, see Model.delete_instance().

classmethod raw(sql, *params)
Parameters:
  • sql – a string SQL expression
  • params – any number of parameters to interpolate
Return type:

a RawQuery for the given Model

Example selecting rows from the User table:

q = User.raw('select id, username from users')
for user in q:
    print user.id, user.username

Note

Generally the use of raw is reserved for those cases where you can significantly optimize a select query. It is useful for select queries since it will return instances of the model.

classmethod create(**attributes)
Parameters:attributes – key/value pairs of model attributes
Return type:a model instance with the provided attributes

Example showing the creation of a user (a row will be added to the database):

user = User.create(username='admin', password='test')

Note

The create() method is a shorthand for instantiate-then-save.

classmethod get(*args, **kwargs)
Parameters:
  • args – a list of query expressions, e.g. User.username == 'foo'
  • kwargs – a mapping of column + lookup to value, e.g. “age__gt=55”
Return type:

Model instance or raises DoesNotExist exception

Get a single row from the database that matches the given query. Raises a <model-class>.DoesNotExist if no rows are returned:

user = User.get(User.username == username, User.password == password)

This method is also exposed via the SelectQuery, though it takes no parameters:

active = User.select().where(User.active == True)
try:
    users = active.where(User.username == username, User.password == password)
    user = users.get()
except User.DoesNotExist:
    user = None

Note

The get() method is shorthand for selecting with a limit of 1. It has the added behavior of raising an exception when no matching row is found. If more than one row is found, the first row returned by the database cursor will be used.

Warning

the “kwargs” style syntax is provided for compatibility with version 1.0. The expression-style syntax is preferable.

classmethod get_or_create(**attributes)

Deprecated since version 2.0: Because this relies of “django-style” expressions, it has been deprecated as of 2.0. Use Model.get() and Model.create() explicitly.

Parameters:attributes – key/value pairs of model attributes
Return type:a Model instance

Get the instance with the given attributes set. If the instance does not exist it will be created.

Example showing get/create an object cached in the database:

CachedObj.get_or_create(key=key, val=some_val)
classmethod filter(*args, **kwargs)

Deprecated since version 2.0: Use select instead.

Parameters:
  • args – a list of DQ or expression objects
  • kwargs – a mapping of column + lookup to value, e.g. “age__gt=55”
Return type:

SelectQuery with appropriate WHERE clauses

Provides a django-like syntax for building a query. The key difference between filter() and SelectQuery.where() is that filter() supports traversing joins using django’s “double-underscore” syntax:

sq = Entry.filter(blog__title='Some Blog')
classmethod alias()
Return type:ModelAlias instance

The alias() method is used to build queries that use self-joins.

Example:

Parent = Category.alias()
sq = (Category
  .select(Category, Parent)
  .join(Parent, on=(Category.parent == Parent.id))
  .where(Parent.name == 'parent category'))

Note

You must explicitly specify which columns to join on

classmethod create_table([fail_silently=False])
Parameters:fail_silently (bool) – If set to True, the method will check for the existence of the table before attempting to create.

Create the table for the given model.

Example:

database.connect()
SomeModel.create_table()  # Execute the create table query.
classmethod drop_table([fail_silently=False])
Parameters:fail_silently (bool) – If set to True, the query will check for the existence of the table before attempting to remove.

Drop the table for the given model.

Note

Cascading deletes are not handled by this method, nor is the removal of any constraints.

classmethod table_exists()
Return type:Boolean whether the table for this model exists in the database
save([force_insert=False[, only=None]])
Parameters:
  • force_insert (bool) – Whether to force execution of an insert
  • only (list) – A list of fields to persist – when supplied, only the given fields will be persisted.

Save the given instance, creating or updating depending on whether it has a primary key. If force_insert=True an INSERT will be issued regardless of whether or not the primary key exists.

Example showing saving a model instance:

user = User()
user.username = 'some-user'  # does not touch the database
user.save()  # change is persisted to the db
delete_instance([recursive=False[, delete_nullable=False]])
Parameters:
  • recursive – Delete this instance and anything that depends on it, optionally updating those that have nullable dependencies
  • delete_nullable – If doing a recursive delete, delete all dependent objects regardless of whether it could be updated to NULL

Delete the given instance. Any foreign keys set to cascade on delete will be deleted automatically. For more programmatic control, you can call with recursive=True, which will delete any non-nullable related models (those that are nullable will be set to NULL). If you wish to delete all dependencies regardless of whether they are nullable, set delete_nullable=True.

example:

some_obj.delete_instance()  # it is gone forever
dependencies([search_nullable=False])
Parameters:search_nullable (bool) – Search models related via a nullable foreign key
Return type:Generator expression yielding queries and foreign key fields

Generate a list of queries of dependent models. Yields a 2-tuple containing the query and corresponding foreign key field. Useful for searching dependencies of a model, i.e. things that would be orphaned in the event of a delete.

Fields

class Field(null=False, index=False, unique=False, verbose_name=None, help_text=None, db_column=None, default=None, choices=None, *args, **kwargs)

The base class from which all other field types extend.

Parameters:
  • null (bool) – whether this column can accept None or NULL values
  • index (bool) – whether to create an index for this column when creating the table
  • unique (bool) – whether to create a unique index for this column when creating the table
  • verbose_name (string) – specify a “verbose name” for this field, useful for metadata purposes
  • help_text (string) – specify some instruction text for the usage/meaning of this field
  • db_column (string) – column name to use for underlying storage, useful for compatibility with legacy databases
  • default – a value to use as an uninitialized default
  • choices – an iterable of 2-tuples mapping value to display
  • primary_key (bool) – whether to use this as the primary key for the table
  • sequence (string) – name of sequence (if backend supports it)
  • kwargs – named attributes containing values that may pertain to specific field subclasses, such as “max_length” or “decimal_places”
db_field = '<some field type>'

Attribute used to map this field to a column type, e.g. “string” or “datetime”

template = '%(column_type)s'

A template for generating the SQL for this field

_is_bound

Boolean flag indicating if the field is attached to a model class.

model_class

The model the field belongs to. Only applies to bound fields.

name

The name of the field. Only applies to bound fields.

db_value(value)
Parameters:value – python data type to prep for storage in the database
Return type:converted python datatype
python_value(value)
Parameters:value – data coming from the backend storage
Return type:python data type
coerce(value)

This method is a shorthand that is used, by default, by both db_value and python_value. You can usually get away with just implementing this.

Parameters:value – arbitrary data from app or backend
Return type:python data type
field_attributes()

This method is responsible for return a dictionary containing the default field attributes for the column, e.g. {'max_length': 255}

Return type:a python dictionary
between(low, high)

Return an expression suitable for performing “BETWEEN” queries.

Return type:an Expression object.
# select employees making between $50 and $60
Employee.select().where(Employee.salary.between(50, 60))
class IntegerField

Stores: integers

db_field = 'int'
class BigIntegerField

Stores: big integers

db_field = 'bigint'
class PrimaryKeyField

Stores: auto-incrementing integer fields suitable for use as primary key.

db_field = 'primary_key'
class FloatField

Stores: floating-point numbers

db_field = 'float'
class DoubleField

Stores: double-precision floating-point numbers

db_field = 'double'
class DecimalField

Stores: decimal numbers, using python standard library Decimal objects

Additional attributes and values:

max_digits 10
decimal_places 5
auto_round False
rounding decimal.DefaultContext.rounding
db_field = 'decimal'
template = '%(column_type)s(%(max_digits)d, %(decimal_places)d)'
class CharField

Stores: small strings (0-255 bytes)

Additional attributes and values:

max_length 255
db_field = 'string'
template = '%(column_type)s(%(max_length)s)'
class TextField

Stores: arbitrarily large strings

db_field = 'text'
class DateTimeField

Stores: python datetime.datetime instances

Accepts a special parameter formats, which contains a list of formats the datetime can be encoded with. The default behavior is:

'%Y-%m-%d %H:%M:%S.%f' # year-month-day hour-minute-second.microsecond
'%Y-%m-%d %H:%M:%S' # year-month-day hour-minute-second
'%Y-%m-%d' # year-month-day

Note

If the incoming value does not match a format, it will be returned as-is

db_field = 'datetime'
year

An expression suitable for extracting the year, for example to retrieve all blog posts from 2013:

Blog.select().where(Blog.pub_date.year == 2013)
month

Same as year, except extract month.

day

Same as year, except extract day.

hour

Same as year, except extract hour.

minute

Same as year, except extract minute.

second

Same as year, except extract second..

class DateField

Stores: python datetime.date instances

Accepts a special parameter formats, which contains a list of formats the date can be encoded with. The default behavior is:

'%Y-%m-%d' # year-month-day
'%Y-%m-%d %H:%M:%S' # year-month-day hour-minute-second
'%Y-%m-%d %H:%M:%S.%f' # year-month-day hour-minute-second.microsecond

Note

If the incoming value does not match a format, it will be returned as-is

db_field = 'date'
year

An expression suitable for extracting the year, for example to retrieve all people born in 1980:

Person.select().where(Person.dob.year == 1983)
month

Same as year, except extract month.

day

Same as year, except extract day.

class TimeField

Stores: python datetime.time instances

Accepts a special parameter formats, which contains a list of formats the time can be encoded with. The default behavior is:

'%H:%M:%S.%f' # hour:minute:second.microsecond
'%H:%M:%S' # hour:minute:second
'%H:%M' # hour:minute
'%Y-%m-%d %H:%M:%S.%f' # year-month-day hour-minute-second.microsecond
'%Y-%m-%d %H:%M:%S' # year-month-day hour-minute-second

Note

If the incoming value does not match a format, it will be returned as-is

db_field = 'time'
hour

Extract the hour from a time, for example to retreive all events occurring in the evening:

Event.select().where(Event.time.hour > 17)
minute

Same as hour, except extract minute.

second

Same as hour, except extract second..

class BooleanField

Stores: True / False

db_field = 'bool'
class ForeignKeyField(rel_model[, related_name=None[, cascade=False[, ...]]])

Stores: relationship to another model

Parameters:
  • rel_model – related Model class or the string ‘self’ if declaring a self-referential foreign key
  • related_name (string) – attribute to expose on related model
  • cascade (bool) – set up foreign key to do cascading deletes
class User(Model):
    name = CharField()

class Tweet(Model):
    user = ForeignKeyField(User, related_name='tweets')
    content = TextField()

# "user" attribute
>>> some_tweet.user
<User: charlie>

# "tweets" related name attribute
>>> for tweet in charlie.tweets:
...     print tweet.content
Some tweet
Another tweet
Yet another tweet

Note

Foreign keys do not have a particular db_field as they will take their field type depending on the type of primary key on the model they are related to.

class CompositeKey(*fields)

Specify a composite primary key for a model. Unlike the other fields, a composite key is defined in the model’s Meta class after the fields have been defined. It takes as parameters the string names of the fields to use as the primary key:

class BlogTagThrough(Model):
    blog = ForeignKeyField(Blog, related_name='tags')
    tag = ForeignKeyField(Tag, related_name='blogs')

    class Meta:
        primary_key = CompositeKey('blog', 'tag')

Query Types

class Query

The parent class from which all other query classes are drived.

where(*expressions)
Parameters:expressions – a list of one or more expressions
Return type:a Query instance

Example selection users where the username is equal to ‘somebody’:

sq = SelectQuery(User).where(User.username == 'somebody')

Example selecting tweets made by users who are either editors or administrators:

sq = SelectQuery(Tweet).join(User).where(
    (User.is_editor == True) |
    (User.is_admin == True))

Example of deleting tweets by users who are no longer active:

dq = DeleteQuery(Tweet).where(
    Tweet.user << User.select().where(User.active == False))
dq.execute()  # perform the delete query

Note

where() calls are chainable. Multiple calls will be “AND”-ed together.

join(model, join_type=None, on=None)
Parameters:
  • model – the model to join on. there must be a ForeignKeyField between the current query context and the model passed in.
  • join_type – allows the type of JOIN used to be specified explicitly, one of JOIN_INNER, JOIN_LEFT_OUTER, JOIN_FULL
  • on – if multiple foreign keys exist between two models, this parameter is the ForeignKeyField to join on.
Return type:

a Query instance

Generate a JOIN clause from the current query context to the model passed in, and establishes model as the new query context.

Example selecting tweets and joining on user in order to restrict to only those tweets made by “admin” users:

sq = SelectQuery(Tweet).join(User).where(User.is_admin == True)

Example selecting users and joining on a particular foreign key field. See the example app for a real-life usage:

sq = SelectQuery(User).join(Relationship, on=Relationship.to_user)
switch(model)
Parameters:model – model to switch the query context to.
Return type:a clone of the query with a new query context

Switches the query context to the given model. Raises an exception if the model has not been selected or joined on previously. Useful for performing multiple joins from a single table.

The following example selects from blog and joins on both entry and user:

sq = SelectQuery(Blog).join(Entry).switch(Blog).join(User)
filter(*args, **kwargs)

Deprecated since version 2.0: Use instead Query.where()

Parameters:
  • args – a list of DQ or Node objects
  • kwargs – a mapping of column + lookup to value, e.g. “age__gt=55”
Return type:

SelectQuery with appropriate WHERE clauses

Provides a django-like syntax for building a query. The key difference between filter() and SelectQuery.where() is that filter() supports traversing joins using django’s “double-underscore” syntax:

sq = Entry.filter(blog__title='Some Blog')

This method is chainable:

base_q = User.filter(active=True)
some_user = base_q.filter(username='charlie')

Note

this method is provided for compatibility with peewee 1.

alias(alias=None)
Parameters:alias (str) – A string to alias the result of this query
Return type:a Query instance

Assign an alias to given query, which can be used as part of a subquery.

sql()
Return type:a 2-tuple containing the appropriate SQL query and a tuple of parameters
execute()

Execute the given query

scalar([as_tuple=False])
Parameters:as_tuple (bool) – return the row as a tuple or a single value
Return type:the resulting row, either as a single value or tuple

Provide a way to retrieve single values from select queries, for instance when performing an aggregation.

>>> PageView.select(fn.Count(fn.Distinct(PageView.url))).scalar()
100 # <-- there are 100 distinct URLs in the pageview table
class SelectQuery(model, *selection)

By far the most complex of the query classes available in peewee. It supports all clauses commonly associated with select queries.

Methods on the select query can be chained together.

SelectQuery implements an __iter__() method, allowing it to be iterated to return model instances.

Parameters:
  • model – a Model class to perform query on
  • selection – a list of models, fields, functions or expressions

If no selection is provided, it will default to all the fields of the given model.

Example selecting some user instances from the database. Only the id and username columns are selected. When iterated, will return instances of the User model:

sq = SelectQuery(User, User.id, User.username)
for user in sq:
    print user.username

Example selecting users and additionally the number of tweets made by the user. The User instances returned will have an additional attribute, ‘count’, that corresponds to the number of tweets made:

sq = (SelectQuery(
    User, User, fn.Count(Tweet.id).alias('count'))
    .join(Tweet)
    .group_by(User))
group_by(*clauses)
Parameters:clauses – a list of expressions, which can be model classes or individual field instances
Return type:SelectQuery

Group by one or more columns. If a model class is provided, all the fields on that model class will be used.

Example selecting users, joining on tweets, and grouping by the user so a count of tweets can be calculated for each user:

sq = (User
    .select(User, fn.Count(Tweet.id).alias('count'))
    .join(Tweet)
    .group_by(User))
having(*expressions)
Parameters:expressions – a list of one or more expressions
Return type:SelectQuery

Here is the above example selecting users and tweet counts, but restricting the results to those users who have created 100 or more tweets:

sq = (User
    .select(User, fn.Count(Tweet.id).alias('count'))
    .join(Tweet)
    .group_by(User)
    .having(fn.Count(Tweet.id) > 100))
order_by(*clauses)
Parameters:clauses – a list of fields, calls to field.[asc|desc]() or one or more expressions
Return type:SelectQuery

Example of ordering users by username:

User.select().order_by(User.username)

Example of selecting tweets and ordering them first by user, then newest first:

Tweet.select().join(User).order_by(
    User.username, Tweet.created_date.desc())

A more complex example ordering users by the number of tweets made (greatest to least), then ordered by username in the event of a tie:

tweet_ct = fn.Count(Tweet.id)
sq = (User
    .select(User, tweet_ct.alias('count'))
    .join(Tweet)
    .group_by(User)
    .order_by(tweet_ct.desc(), User.username))
limit(num)
Parameters:num (int) – limit results to num rows
offset(num)
Parameters:num (int) – offset results by num rows
paginate(page_num, paginate_by=20)
Parameters:
  • page_num – a 1-based page number to use for paginating results
  • paginate_by – number of results to return per-page
Return type:

SelectQuery

Shorthand for applying a LIMIT and OFFSET to the query.

User.select().order_by(User.username).paginate(3, 20)  # get users 41-60
distinct()
Return type:SelectQuery

indicates that this query should only return distinct rows. results in a SELECT DISTINCT query.

for_update([for_update=True[, nowait=False]])
Return type:SelectQuery

Indicate that this query should lock rows for update. If nowait is True then the database will raise an OperationalError if it cannot obtain the lock.

naive()
Return type:SelectQuery

Flag this query indicating it should only attempt to reconstruct a single model instance for every row returned by the cursor. If multiple tables were queried, the columns returned are patched directly onto the single model instance.

Generally this method is useful for speeding up the time needed to construct model instances given a database cursor.

Note

this can provide a significant speed improvement when doing simple iteration over a large result set.

iterator()
Return type:iterable

By default peewee will cache rows returned by the cursor. This is to prevent things like multiple iterations, slicing and indexing from triggering extra queries. When you are iterating over a large number of rows, however, this cache can take up a lot of memory. Using iterator() will save memory by not storing all the returned model instances.

# iterate over large number of rows.
for obj in Stats.select().iterator():
    # do something.
    pass
tuples()
Return type:SelectQuery

Flag this query indicating it should simply return raw tuples from the cursor. This method is useful when you either do not want or do not need full model instances.

dicts()
Return type:SelectQuery

Flag this query indicating it should simply return dictionaries from the cursor. This method is useful when you either do not want or do not need full model instances.

annotate(related_model, aggregation=None)
Parameters:
  • related_model – related Model on which to perform aggregation, must be linked by ForeignKeyField.
  • aggregation – the type of aggregation to use, e.g. fn.Count(Tweet.id).alias('count')
Return type:

SelectQuery

Annotate a query with an aggregation performed on a related model, for example, “get a list of users with the number of tweets for each”:

>>> User.select().annotate(Tweet)

If aggregation is None, it will default to fn.Count(related_model.id).alias('count') but can be anything:

>>> user_latest = User.select().annotate(Tweet, fn.Max(Tweet.created_date).alias('latest'))

Note

If the ForeignKeyField is nullable, then a LEFT OUTER join may need to be used:

User.select().join(Tweet, JOIN_LEFT_OUTER).annotate(Tweet)
aggregate(aggregation)
Parameters:aggregation – a function specifying what aggregation to perform, for example fn.Max(Tweet.created_date).

Method to look at an aggregate of rows using a given function and return a scalar value, such as the count of all rows or the average value of a particular column.

count()
Return type:an integer representing the number of rows in the current query
>>> sq = SelectQuery(Tweet)
>>> sq.count()
45  # number of tweets
>>> sq.where(Tweet.status == DELETED)
>>> sq.count()
3  # number of tweets that are marked as deleted
wrapped_count()
Return type:an integer representing the number of rows in the current query

Wrap the count query in a subquery. Additional overhead but will give correct counts when performing DISTINCT queries or those with GROUP BY clauses.

Note

count() will automatically default to wrapped_count() in the event the query is distinct or has a grouping.

exists()
Return type:boolean whether the current query will return any rows. uses an optimized lookup, so use this rather than get().
sq = User.select().where(User.active == True)
if sq.where(User.username == username, User.password == password).exists():
    authenticated = True
get()
Return type:Model instance or raises DoesNotExist exception

Get a single row from the database that matches the given query. Raises a <model-class>.DoesNotExist if no rows are returned:

active = User.select().where(User.active == True)
try:
    user = active.where(User.username == username).get()
except User.DoesNotExist:
    user = None

This method is also exposed via the Model api, in which case it accepts arguments that are translated to the where clause:

user = User.get(User.active == True, User.username == username)
first()
Return type:Model instance or None if no results

Fetch the first row from a query. The result will be cached in case the entire query result-set should be iterated later.

execute()
Return type:QueryResultWrapper

Executes the query and returns a QueryResultWrapper for iterating over the result set. The results are managed internally by the query and whenever a clause is added that would possibly alter the result set, the query is marked for re-execution.

__iter__()

Executes the query and returns populated model instances:

for user in User.select().where(User.active == True):
    print user.username
class UpdateQuery(model, **kwargs)
Parameters:
  • modelModel class on which to perform update
  • kwargs – mapping of field/value pairs containing columns and values to update

Example in which users are marked inactive if their registration expired:

uq = UpdateQuery(User, active=False).where(User.registration_expired == True)
uq.execute()  # Perform the actual update

Example of an atomic update:

atomic_update = UpdateQuery(PageCount, count = PageCount.count + 1).where(
    PageCount.url == url)
atomic_update.execute()  # will perform the actual update
execute()
Return type:Number of rows updated

Performs the query

class InsertQuery(model, **kwargs)

Creates an InsertQuery instance for the given model where kwargs is a dictionary of field name to value:

>>> iq = InsertQuery(User, username='admin', password='test', active=True)
>>> iq.execute()  # insert new row and return primary key
2L
execute()
Return type:primary key of the new row

Performs the query

class DeleteQuery

Creates a DeleteQuery instance for the given model.

Note

DeleteQuery will not traverse foreign keys or ensure that constraints are obeyed, so use it with care.

Example deleting users whose account is inactive:

dq = DeleteQuery(User).where(User.active == False)
execute()
Return type:Number of rows deleted

Performs the query

class RawQuery

Allows execution of an arbitrary query and returns instances of the model via a QueryResultsWrapper.

Note

Generally you will only need this for executing highly optimized SELECT queries.

Warning

If you are executing a parameterized query, you must use the correct interpolation string for your database. SQLite uses '?' and most others use '%s'.

Example selecting users with a given username:

>>> rq = RawQuery(User, 'SELECT * FROM users WHERE username = ?', 'admin')
>>> for obj in rq.execute():
...     print obj
<User: admin>
tuples()
Return type:RawQuery

Flag this query indicating it should simply return raw tuples from the cursor. This method is useful when you either do not want or do not need full model instances.

dicts()
Return type:RawQuery

Flag this query indicating it should simply return raw dicts from the cursor. This method is useful when you either do not want or do not need full model instances.

execute()
Return type:a QueryResultWrapper for iterating over the result set. The results are instances of the given model.

Performs the query

prefetch(sq, *subqueries)
Parameters:
  • sqSelectQuery instance
  • subqueries – one or more SelectQuery instances to prefetch for sq. You can also pass models, but they will be converted into SelectQueries.
Return type:

SelectQuery with related instances pre-populated

Pre-fetch the appropriate instances from the subqueries and apply them to their corresponding parent row in the outer query. This function will eagerly load the related instances specified in the subqueries. This is a technique used to save doing O(n) queries for n rows, and rather is O(k) queries for k subqueries.

For example, consider you have a list of users and want to display all their tweets:

# let's impost some small restrictions on our queries
users = User.select().where(User.active == True)
tweets = Tweet.select().where(Tweet.published == True)

# this will perform 2 queries
users_pf = prefetch(users, tweets)

# now we can:
for user in users_pf:
    print user.username
    for tweet in user.tweets_prefetch:
        print '- ', tweet.content

You can prefetch an arbitrary number of items. For instance, suppose we have a photo site, User -> Photo -> (Comments, Tags). That is, users can post photos, and these photos can have tags and comments on them. If we wanted to fetch a list of users, all their photos, and all the comments and tags on the photos:

users = User.select()
published_photos = Photo.select().where(Photo.published == True)
published_comments = Comment.select().where(
    (Comment.is_spam == False) &
    (Comment.num_flags < 3))

# note that we are just passing the Tag model -- it will be converted
# to a query automatically
users_pf = prefetch(users, published_photos, published_comments, Tag)

# now we can iterate users, photos, and comments/tags
for user in users_pf:
    for photo in user.photo_set_prefetch:
        for comment in photo.comment_set_prefetch:
            # ...
        for tag in photo.tag_set_prefetch:
            # ...

Note

Subqueries must be related by foreign key and can be arbitrarily deep

Warning

prefetch() can use up lots of RAM when the result set is large, and will not warn you if you are doing something dangerous, so it is up to you to know when to use it. Additionally, because of the semantics of subquerying, there may be some cases when prefetch does not act as you expect (for instnace, when applying a LIMIT to subqueries, but there may be others) – please report anything you think is a bug to github.

Database and its subclasses

class Database(database[, threadlocals=False[, autocommit=True[, fields=None[, ops=None[, **connect_kwargs]]]]])
Parameters:
  • database – the name of the database (or filename if using sqlite)
  • threadlocals – whether to store connections in a threadlocal
  • autocommit – automatically commit every query executed by calling execute()
  • fields (dict) – a mapping of db_field to database column type, e.g. ‘string’ => ‘varchar’
  • ops (dict) – a mapping of operations understood by the querycompiler to expressions
  • connect_kwargs – any arbitrary parameters to pass to the database driver when connecting

Note

if your database name is not known when the class is declared, you can pass None in as the database name which will mark the database as “deferred” and any attempt to connect while in this state will raise an exception. To initialize your database, call the Database.init() method with the database name

A high-level api for working with the supported database engines. Database provides a wrapper around some of the functions performed by the Adapter, in addition providing support for:

  • execution of SQL queries
  • creating and dropping tables and indexes
commit_select = False

Whether to issue a commit after executing a select query. With some engines can prevent implicit transactions from piling up.

compiler_class = QueryCompiler

A class suitable for compiling queries

field_overrides = {}

A mapping of field types to database column types, e.g. {'primary_key': 'SERIAL'}

for_update = False

Whether the given backend supports selecting rows for update

interpolation = '?'

The string used by the driver to interpolate query parameters

op_overrides = {}

A mapping of operation codes to string operations, e.g. {OP_LIKE: 'LIKE BINARY'}

quote_char = '"'

The string used by the driver to quote names

reserved_tables = []

Table names that are reserved by the backend – if encountered in the application a warning will be issued.

sequences = False

Whether the given backend supports sequences

subquery_delete_same_table = True

Whether the given backend supports deleting rows using a subquery that selects from the same table

init(database[, **connect_kwargs])

If the database was instantiated with database=None, the database is said to be in a ‘deferred’ state (see notes) – if this is the case, you can initialize it at any time by calling the init method.

Parameters:
  • database – the name of the database (or filename if using sqlite)
  • connect_kwargs – any arbitrary parameters to pass to the database driver when connecting
connect()

Establishes a connection to the database

Note

If you initialized with threadlocals=True, then this will store the connection inside a threadlocal, ensuring that connections are not shared across threads.

close()

Closes the connection to the database (if one is open)

Note

If you initialized with threadlocals=True, only a connection local to the calling thread will be closed.

get_conn()
Return type:a connection to the database, creates one if does not exist
get_cursor()
Return type:a cursor for executing queries
last_insert_id(cursor, model)
Parameters:
  • cursor – the database cursor used to perform the insert query
  • model – the model class that was just created
Return type:

the primary key of the most recently inserted instance

rows_affected(cursor)
Return type:number of rows affected by the last query
compiler()
Return type:an instance of QueryCompiler using the field and op overrides specified.
execute_sql(sql[, params=None[, require_commit=True]])
Parameters:
  • sql – a string sql query
  • params – a list or tuple of parameters to interpolate

Note

You can configure whether queries will automatically commit by using the set_autocommit() and Database.get_autocommit() methods.

begin()

Initiate a new transaction. By default not implemented as this is not part of the DB-API 2.0, but provided for API compatibility.

commit()

Call commit() on the active connection, committing the current transaction

rollback()

Call rollback() on the active connection, rolling back the current transaction

set_autocommit(autocommit)
Parameters:autocommit – a boolean value indicating whether to turn on/off autocommit for the current connection
get_autocommit()
Return type:a boolean value indicating whether autocommit is on for the current connection
get_tables()
Return type:a list of table names in the database

Warning

Not implemented – implementations exist in subclasses

get_indexes_for_table(table)
Parameters:table – the name of table to introspect
Return type:a list of (index_name, is_unique) tuples

Warning

Not implemented – implementations exist in subclasses

sequence_exists(sequence_name)
Rtype boolean:

Warning

Not implemented – implementations exist in subclasses

create_table(model_class)
Parameters:model_classModel class to create table for
create_index(model_class, fields[, unique=False])
Parameters:
  • model_classModel table on which to create index
  • fields – field(s) to create index on (either field instances or field names)
  • unique – whether the index should enforce uniqueness
create_foreign_key(model_class, field)
Parameters:
  • model_classModel table on which to create foreign key index / constraint
  • fieldField object
create_sequence(sequence_name)
Parameters:sequence_name – name of sequence to create

Note

only works with database engines that support sequences

drop_table(model_class[, fail_silently=False])
Parameters:
  • model_classModel table to drop
  • fail_silently – if True, query will add a IF EXISTS clause

Note

Cascading drop tables are not supported at this time, so if a constraint exists that prevents a table being dropped, you will need to handle that in application logic.

drop_sequence(sequence_name)
Parameters:sequence_name – name of sequence to drop

Note

only works with database engines that support sequences

transaction()

Return a context manager that executes statements in a transaction. If an error is raised inside the context manager, the transaction will be rolled back, otherwise statements are committed when exiting.

# delete a blog instance and all its associated entries, but
# do so within a transaction
with database.transaction():
    blog.delete_instance(recursive=True)
commit_on_success(func)

Decorator that wraps the given function in a single transaction, which, upon success will be committed. If an error is raised inside the function, the transaction will be rolled back and the error will be re-raised.

Nested functions can be wrapped with commit_on_success - the database will keep a stack and only commit when it reaches the end of the outermost function.

Parameters:func – function to decorate
@database.commit_on_success
def transfer_money(from_acct, to_acct, amt):
    from_acct.charge(amt)
    to_acct.pay(amt)
    return amt
savepoint([sid=None])

Return a context manager that executes statements in a savepoint. If an error is raised inside the context manager, the savepoint will be rolled back, otherwise statements are committed when exiting.

Savepoints can be thought of as nested transactions.

Parameters:sid (str) – A string identifier for the savepoint.
classmethod register_fields(fields)

Register a mapping of field overrides for the database class. Used to register custom fields or override the defaults.

Parameters:fields (dict) – A mapping of db_field to column type
classmethod register_ops(ops)

Register a mapping of operations understood by the QueryCompiler to their SQL equivalent, e.g. {OP_EQ: '='}. Used to extend the types of field comparisons.

Parameters:fields (dict) – A mapping of db_field to column type
extract_date(date_part, date_field)

Return an expression suitable for extracting a date part from a date field. For instance, extract the year from a DateTimeField.

Parameters:
  • date_part (str) – The date part attribute to retrieve. Valid options are: “year”, “month”, “day”, “hour”, “minute” and “second”.
  • date_field (Field) – field instance storing a datetime, date or time.
Return type:

an expression object.

sql_error_handler(exception, sql, params, require_commit)

This hook is called when an error is raised executing a query, allowing your application to inject custom error handling behavior. The default implementation simply reraises the exception.

class SqliteDatabaseCustom(SqliteDatabase):
    def sql_error_handler(self, exception, sql, params, require_commit):
        # Perform some custom behavior, for example close the
        # connection to the database.
        self.close()

        # Re-raise the exception.
        raise exception
class SqliteDatabase(Database)

Database subclass that communicates to the “sqlite3” driver

class MySQLDatabase(Database)

Database subclass that communicates to the “MySQLdb” driver

class PostgresqlDatabase(Database)

Database subclass that communicates to the “psycopg2” driver

Misc

class fn

A helper class that will convert arbitrary function calls to SQL function calls.

To express functions in peewee, use the fn object. The way it works is anything to the right of the “dot” operator will be treated as a function. You can pass that function arbitrary parameters which can be other valid expressions.

For example:

Peewee expression Equivalent SQL
fn.Count(Tweet.id).alias('count') Count(t1."id") AS count
fn.Lower(fn.Substr(User.username, 1, 1)) Lower(Substr(t1."username", 1, 1))
fn.Rand().alias('random') Rand() AS random
fn.Stddev(Employee.salary).alias('sdv') Stddev(t1."salary") AS sdv
class Proxy

Proxy class useful for situations when you wish to defer the initialization of an object. For instance, you want to define your models but you do not know what database engine you will be using until runtime.

Example:

database_proxy = Proxy()  # Create a proxy for our db.

class BaseModel(Model):
    class Meta:
        database = database_proxy  # Use proxy for our DB.

class User(BaseModel):
    username = CharField()

# Based on configuration, use a different database.
if app.config['DEBUG']:
    database = SqliteDatabase('local.db')
elif app.config['TESTING']:
    database = SqliteDatabase(':memory:')
else:
    database = PostgresqlDatabase('mega_production_db')

# Configure our proxy to use the db we specified in config.
database_proxy.initialize(database)
initialize(obj)
Parameters:obj – The object to proxy to.

Once initialized, the attributes and methods on obj can be accessed directly via the Proxy instance.

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