sqlite3.rst

sqlite3 --- DB-API 2.0 interface for SQLite databases

sqlite3

Gerhard Häring <gh@ghaering.de>

Source code: Lib/sqlite3/

import sqlite3 src = sqlite3.connect(":memory:", isolation_level=None) dst = sqlite3.connect("tutorial.db", isolation_level=None) src.backup(dst) del src, dst

SQLite is a C library that provides a lightweight disk-based database that doesn't require a separate server process and allows accessing the database using a nonstandard variant of the SQL query language. Some applications can use SQLite for internal data storage. It's also possible to prototype an application using SQLite and then port the code to a larger database such as PostgreSQL or Oracle.

The !sqlite3 module was written by Gerhard Häring. It provides an SQL interface compliant with the DB-API 2.0 specification described by 249, and requires SQLite 3.7.15 or newer.

This document includes four main sections:

• sqlite3-tutorial teaches how to use the !sqlite3 module.
• sqlite3-reference describes the classes and functions this module defines.
• sqlite3-howtos details how to handle specific tasks.
• sqlite3-explanation provides in-depth background on transaction control.

https://www.sqlite.org

The SQLite web page; the documentation describes the syntax and the available data types for the supported SQL dialect.

https://www.w3schools.com/sql/

Tutorial, reference and examples for learning SQL syntax.

249 - Database API Specification 2.0

PEP written by Marc-André Lemburg.

Tutorial

In this tutorial, you will create a database of Monty Python movies using basic !sqlite3 functionality. It assumes a fundamental understanding of database concepts, including cursors and transactions.

First, we need to create a new database and open a database connection to allow !sqlite3 to work with it. Call sqlite3.connect to to create a connection to the database tutorial.db in the current working directory, implicitly creating it if it does not exist:

import sqlite3 con = sqlite3.connect("tutorial.db")

The returned Connection object con represents the connection to the on-disk database.

In order to execute SQL statements and fetch results from SQL queries, we will need to use a database cursor. Call con.cursor() <Connection.cursor> to create the Cursor:

cur = con.cursor()

Now that we've got a database connection and a cursor, we can create a database table movie with columns for title, release year, and review score. For simplicity, we can just use column names in the table declaration --thanks to the flexible typing feature of SQLite, specifying the data types is optional. Execute the CREATE TABLE statement by calling cur.execute(...) <Cursor.execute>:

cur.execute("CREATE TABLE movie(title, year, score)")

We can verify that the new table has been created by querying the sqlite_master table built-in to SQLite, which should now contain an entry for the movie table definition (see The Schema Table for details). Execute that query by calling cur.execute(...) <Cursor.execute>, assign the result to res, and call res.fetchone() <Cursor.fetchone> to fetch the resulting row:

>>> res = cur.execute("SELECT name FROM sqlite_master") >>> res.fetchone() ('movie',)

We can see that the table has been created, as the query returns a tuple containing the table's name. If we query sqlite_master for a non-existent table spam, !res.fetchone() will return None:

>>> res = cur.execute("SELECT name FROM sqlite_master WHERE name='spam'") >>> res.fetchone() is None True

Now, add two rows of data supplied as SQL literals by executing an INSERT statement, once again by calling cur.execute(...) <Cursor.execute>:

cur.execute("""

INSERT INTO movie VALUES

('Monty Python and the Holy Grail', 1975, 8.2), ('And Now for Something Completely Different', 1971, 7.5)

""")

The INSERT statement implicitly opens a transaction, which needs to be committed before changes are saved in the database (see sqlite3-controlling-transactions for details). Call con.commit() <Connection.commit> on the connection object to commit the transaction:

con.commit()

We can verify that the data was inserted correctly by executing a SELECT query. Use the now-familiar cur.execute(...) <Cursor.execute> to assign the result to res, and call res.fetchall() <Cursor.fetchall> to return all resulting rows:

>>> res = cur.execute("SELECT score FROM movie") >>> res.fetchall() [(8.2,), (7.5,)]

The result is a list of two !tuples, one per row, each containing that row's score value.

Now, insert three more rows by calling cur.executemany(...) <Cursor.executemany>:

data = [

("Monty Python Live at the Hollywood Bowl", 1982, 7.9), ("Monty Python's The Meaning of Life", 1983, 7.5), ("Monty Python's Life of Brian", 1979, 8.0),

] cur.executemany("INSERT INTO movie VALUES(?, ?, ?)", data) con.commit() # Remember to commit the transaction after executing INSERT.

Notice that ? placeholders are used to bind data to the query. Always use placeholders instead of string formatting <tut-formatting> to bind Python values to SQL statements, to avoid SQL injection attacks (see sqlite3-placeholders for more details).

We can verify that the new rows were inserted by executing a SELECT query, this time iterating over the results of the query:

>>> for row in cur.execute("SELECT year, title FROM movie ORDER BY year"): ... print(row) (1971, 'And Now for Something Completely Different') (1975, 'Monty Python and the Holy Grail') (1979, "Monty Python's Life of Brian") (1982, 'Monty Python Live at the Hollywood Bowl') (1983, "Monty Python's The Meaning of Life")

Each row is a two-item tuple of (year, title), matching the columns selected in the query.

Finally, verify that the database has been written to disk by calling con.close() <Connection.close> to close the existing connection, opening a new one, creating a new cursor, then querying the database:

>>> con.close() >>> new_con = sqlite3.connect("tutorial.db") >>> new_cur = new_con.cursor() >>> res = new_cur.execute("SELECT title, year FROM movie ORDER BY score DESC") >>> title, year = res.fetchone() >>> print(f'The highest scoring Monty Python movie is {title!r}, released in {year}') The highest scoring Monty Python movie is 'Monty Python and the Holy Grail', released in 1975

You've now created an SQLite database using the !sqlite3 module, inserted data and retrieved values from it in multiple ways.

• sqlite3-howtos for further reading:

  • sqlite3-placeholders
  • sqlite3-adapters
  • sqlite3-converters
  • sqlite3-connection-context-manager

• sqlite3-explanation for in-depth background on transaction control.

Reference

Module functions

connect(database, timeout=5.0, detect_types=0, isolation_level="DEFERRED", check_same_thread=True, factory=sqlite3.Connection, cached_statements=128, uri=False)

Open a connection to an SQLite database.

param database

The path to the database file to be opened. Pass ":memory:" to open a connection to a database that is in RAM instead of on disk.

type database

path-like object

param float timeout

How many seconds the connection should wait before raising an exception, if the database is locked by another connection. If another connection opens a transaction to modify the database, it will be locked until that transaction is committed. Default five seconds.

param int detect_types

Control whether and how data types not natively supported by SQLite <sqlite3-types> are looked up to be converted to Python types, using the converters registered with register_converter. Set it to any combination (using |, bitwise or) of PARSE_DECLTYPES and PARSE_COLNAMES to enable this. Column names takes precedence over declared types if both flags are set. Types cannot be detected for generated fields (for example max(data)), even when the detect_types parameter is set; str will be returned instead. By default (0), type detection is disabled.

param isolation_level

The ~Connection.isolation_level of the connection, controlling whether and how transactions are implicitly opened. Can be "DEFERRED" (default), "EXCLUSIVE" or "IMMEDIATE"; or None to disable opening transactions implicitly. See sqlite3-controlling-transactions for more.

type isolation_level

str | None

param bool check_same_thread

If True (default), only the creating thread may use the connection. If False, the connection may be shared across multiple threads; if so, write operations should be serialized by the user to avoid data corruption.

param Connection factory

A custom subclass of Connection to create the connection with, if not the default Connection class.

param int cached_statements

The number of statements that !sqlite3 should internally cache for this connection, to avoid parsing overhead. By default, 128 statements.

param bool uri

If set to True, database is interpreted as a URI (Uniform Resource Identifier) with a file path and an optional query string. The scheme part must be "file:", and the path can be relative or absolute. The query string allows passing parameters to SQLite, enabling various sqlite3-uri-tricks.

rtype

Connection

sqlite3.connect database sqlite3.connect

sqlite3.connect/handle connection_handle sqlite3.connect

3.4 The uri parameter.

3.7 database can now also be a path-like object, not only a string.

3.10 The sqlite3.connect/handle auditing event.

complete_statement(statement)

Return True if the string statement appears to contain one or more complete SQL statements. No syntactic verification or parsing of any kind is performed, other than checking that there are no unclosed string literals and the statement is terminated by a semicolon.

For example:

>>> sqlite3.complete_statement("SELECT foo FROM bar;") True >>> sqlite3.complete_statement("SELECT foo") False

This function may be useful during command-line input to determine if the entered text seems to form a complete SQL statement, or if additional input is needed before calling ~Cursor.execute.

enable_callback_tracebacks(flag, /)

Enable or disable callback tracebacks. By default you will not get any tracebacks in user-defined functions, aggregates, converters, authorizer callbacks etc. If you want to debug them, you can call this function with flag set to True. Afterwards, you will get tracebacks from callbacks on sys.stderr. Use False to disable the feature again.

Register an unraisable hook handler <sys.unraisablehook> for an improved debug experience:

sqlite3.trace

import sqlite3

sqlite3.trace

>>> sqlite3.enable_callback_tracebacks(True) >>> con = sqlite3.connect(":memory:") >>> def evil_trace(stmt): ... 5/0 >>> con.set_trace_callback(evil_trace) >>> def debug(unraisable): ... print(f"{unraisable.exc_value!r} in callback {unraisable.object.__name__}") ... print(f"Error message: {unraisable.err_msg}") >>> import sys >>> sys.unraisablehook = debug >>> cur = con.execute("SELECT 1") ZeroDivisionError('division by zero') in callback evil_trace Error message: None

register_adapter(type, adapter, /)

Register an adapter callable to adapt the Python type type into an SQLite type. The adapter is called with a Python object of type type as its sole argument, and must return a value of a type that SQLite natively understands <sqlite3-types>.

register_converter(typename, converter, /)

Register the converter callable to convert SQLite objects of type typename into a Python object of a specific type. The converter is invoked for all SQLite values of type typename; it is passed a bytes object and should return an object of the desired Python type. Consult the parameter detect_types of connect for information regarding how type detection works.

Note: typename and the name of the type in your query are matched case-insensitively.

Module constants

PARSE_COLNAMES

Pass this flag value to the detect_types parameter of connect to look up a converter function by using the type name, parsed from the query column name, as the converter dictionary key. The type name must be wrapped in square brackets ([]).

SELECT p as "p [point]" FROM test;  ! will look up converter "point"

This flag may be combined with PARSE_DECLTYPES using the | (bitwise or) operator.

PARSE_DECLTYPES

Pass this flag value to the detect_types parameter of connect to look up a converter function using the declared types for each column. The types are declared when the database table is created. !sqlite3 will look up a converter function using the first word of the declared type as the converter dictionary key. For example:

CREATE TABLE test(
   i integer primary key,  ! will look up a converter named "integer"
   p point,                ! will look up a converter named "point"
   n number(10)            ! will look up a converter named "number"
 )

This flag may be combined with PARSE_COLNAMES using the | (bitwise or) operator.

SQLITE_OK SQLITE_DENY SQLITE_IGNORE

Flags that should be returned by the authorizer_callback callable passed to Connection.set_authorizer, to indicate whether:

• Access is allowed (!SQLITE_OK),
• The SQL statement should be aborted with an error (!SQLITE_DENY)
• The column should be treated as a NULL value (!SQLITE_IGNORE)

apilevel

String constant stating the supported DB-API level. Required by the DB-API. Hard-coded to "2.0".

paramstyle

String constant stating the type of parameter marker formatting expected by the !sqlite3 module. Required by the DB-API. Hard-coded to "qmark".

Note

The !sqlite3 module supports both qmark and numeric DB-API parameter styles, because that is what the underlying SQLite library supports. However, the DB-API does not allow multiple values for the paramstyle attribute.

sqlite_version

Version number of the runtime SQLite library as a string <str>.

sqlite_version_info

Version number of the runtime SQLite library as a tuple of integers <int>.

threadsafety

Integer constant required by the DB-API 2.0, stating the level of thread safety the !sqlite3 module supports. This attribute is set based on the default threading mode the underlying SQLite library is compiled with. The SQLite threading modes are:

1. Single-thread: In this mode, all mutexes are disabled and SQLite is unsafe to use in more than a single thread at once.
2. Multi-thread: In this mode, SQLite can be safely used by multiple threads provided that no single database connection is used simultaneously in two or more threads.
3. Serialized: In serialized mode, SQLite can be safely used by multiple threads with no restriction.

The mappings from SQLite threading modes to DB-API 2.0 threadsafety levels are as follows:

SQLite threading mode	threadsafety	SQLITE_THREADSAFE	DB-API 2.0 meaning
single-thread	0	0	Threads may not share the module
multi-thread	1	2	Threads may share the module, but not connections
serialized	3	1	Threads may share the module, connections and cursors

3.11 Set threadsafety dynamically instead of hard-coding it to 1.

version

Version number of this module as a string <str>. This is not the version of the SQLite library.

version_info

Version number of this module as a tuple of integers <int>. This is not the version of the SQLite library.

Connection objects

Each open SQLite database is represented by a Connection object, which is created using sqlite3.connect. Their main purpose is creating Cursor objects, and sqlite3-controlling-transactions.

• sqlite3-connection-shortcuts
• sqlite3-connection-context-manager

An SQLite database connection has the following attributes and methods:

isolation_level

This attribute controls the transaction handling <sqlite3-controlling-transactions> performed by !sqlite3. If set to None, transactions are never implicitly opened. If set to one of "DEFERRED", "IMMEDIATE", or "EXCLUSIVE", corresponding to the underlying SQLite transaction behaviour, implicit transaction management <sqlite3-controlling-transactions> is performed.

If not overridden by the isolation_level parameter of connect, the default is "", which is an alias for "DEFERRED".

in_transaction

This read-only attribute corresponds to the low-level SQLite autocommit mode.

True if a transaction is active (there are uncommitted changes), False otherwise.

3.2

row_factory

A callable that accepts two arguments, a Cursor object and the raw row results as a tuple, and returns a custom object representing an SQLite row.

Example:

../includes/sqlite3/row_factory.py

If returning a tuple doesn't suffice and you want name-based access to columns, you should consider setting row_factory to the highly optimized sqlite3.Row type. Row provides both index-based and case-insensitive name-based access to columns with almost no memory overhead. It will probably be better than your own custom dictionary-based approach or even a db_row based solution.

text_factory

A callable that accepts a bytes parameter and returns a text representation of it. The callable is invoked for SQLite values with the TEXT data type. By default, this attribute is set to str. If you want to return bytes instead, set text_factory to bytes.

Example:

../includes/sqlite3/text_factory.py

total_changes

Return the total number of database rows that have been modified, inserted, or deleted since the database connection was opened.

cursor(factory=Cursor)

Create and return a Cursor object. The cursor method accepts a single optional parameter factory. If supplied, this must be a callable returning an instance of Cursor or its subclasses.

blobopen(table, column, row, /, *, readonly=False, name="main")

Open a Blob handle to an existing BLOB (Binary Large OBject).

param str table

The name of the table where the blob is located.

param str column

The name of the column where the blob is located.

param str row

The name of the row where the blob is located.

param bool readonly

Set to True if the blob should be opened without write permissions. Defaults to False.

param str name

The name of the database where the blob is located. Defaults to "main".

raises OperationalError

When trying to open a blob in a WITHOUT ROWID table.

rtype

Blob

Note

The blob size cannot be changed using the Blob class. Use the SQL function zeroblob to create a blob with a fixed size.

3.11

commit()

Commit any pending transaction to the database. If there is no open transaction, this method is a no-op.

rollback()

Roll back to the start of any pending transaction. If there is no open transaction, this method is a no-op.

close()

Close the database connection. Any pending transaction is not committed implicitly; make sure to commit before closing to avoid losing pending changes.

execute(sql, parameters=(), /)

Create a new Cursor object and call ~Cursor.execute on it with the given sql and parameters. Return the new cursor object.

executemany(sql, parameters, /)

Create a new Cursor object and call ~Cursor.executemany on it with the given sql and parameters. Return the new cursor object.

executescript(sql_script, /)

Create a new Cursor object and call ~Cursor.executescript on it with the given sql_script. Return the new cursor object.

create_function(name, narg, func, *, deterministic=False)

Create or remove a user-defined SQL function.

param str name

The name of the SQL function.

param int narg

The number of arguments the SQL function can accept. If -1, it may take any number of arguments.

param func

A callable that is called when the SQL function is invoked. The callable must return a type natively supported by SQLite <sqlite3-types>. Set to None to remove an existing SQL function.

type func

callback | None

param bool deterministic

If True, the created SQL function is marked as deterministic, which allows SQLite to perform additional optimizations.

raises NotSupportedError

If deterministic is used with SQLite versions older than 3.8.3.

3.8 The deterministic parameter.

Example:

../includes/sqlite3/md5func.py

create_aggregate(name, /, n_arg, aggregate_class)

Create or remove a user-defined SQL aggregate function.

param str name

The name of the SQL aggregate function.

param int n_arg

The number of arguments the SQL aggregate function can accept. If -1, it may take any number of arguments.

param aggregate_class

A class must implement the following methods:

• step(): Add a row to the aggregate.
• finalize(): Return the final result of the aggregate as a type natively supported by SQLite <sqlite3-types>.

The number of arguments that the step() method must accept is controlled by n_arg.

Set to None to remove an existing SQL aggregate function.

type aggregate_class

class | None

Example:

../includes/sqlite3/mysumaggr.py

create_window_function(name, num_params, aggregate_class, /)

Create or remove a user-defined aggregate window function.

param str name

The name of the SQL aggregate window function to create or remove.

param int num_params

The number of arguments the SQL aggregate window function can accept. If -1, it may take any number of arguments.

param aggregate_class

A class that must implement the following methods:

• step(): Add a row to the current window.
• value(): Return the current value of the aggregate.
• inverse(): Remove a row from the current window.
• finalize(): Return the final result of the aggregate as a type natively supported by SQLite <sqlite3-types>.

The number of arguments that the step() and value() methods must accept is controlled by num_params.

Set to None to remove an existing SQL aggregate window function.

raises NotSupportedError

If used with a version of SQLite older than 3.25.0, which does not support aggregate window functions.

type aggregate_class

class | None

3.11

Example:

../includes/sqlite3/sumintwindow.py

create_collation(name, callable)

Create a collation named name using the collating function callable. callable is passed two string <str> arguments, and it should return an integer <int>:

• 1 if the first is ordered higher than the second
• -1 if the first is ordered lower than the second
• 0 if they are ordered equal

The following example shows a reverse sorting collation:

../includes/sqlite3/collation_reverse.py

Remove a collation function by setting callable to None.

3.11 The collation name can contain any Unicode character. Earlier, only ASCII characters were allowed.

interrupt()

Call this method from a different thread to abort any queries that might be executing on the connection. Aborted queries will raise an exception.

set_authorizer(authorizer_callback)

Register callable authorizer_callback to be invoked for each attempt to access a column of a table in the database. The callback should return one of SQLITE_OK, SQLITE_DENY, or SQLITE_IGNORE to signal how access to the column should be handled by the underlying SQLite library.

The first argument to the callback signifies what kind of operation is to be authorized. The second and third argument will be arguments or None depending on the first argument. The 4th argument is the name of the database ("main", "temp", etc.) if applicable. The 5th argument is the name of the inner-most trigger or view that is responsible for the access attempt or None if this access attempt is directly from input SQL code.

Please consult the SQLite documentation about the possible values for the first argument and the meaning of the second and third argument depending on the first one. All necessary constants are available in the !sqlite3 module.

Passing None as authorizer_callback will disable the authorizer.

3.11 Added support for disabling the authorizer using None.

set_progress_handler(progress_handler, n)

Register callable progress_handler to be invoked for every n instructions of the SQLite virtual machine. This is useful if you want to get called from SQLite during long-running operations, for example to update a GUI.

If you want to clear any previously installed progress handler, call the method with None for progress_handler.

Returning a non-zero value from the handler function will terminate the currently executing query and cause it to raise an OperationalError exception.

set_trace_callback(trace_callback)

Register callable trace_callback to be invoked for each SQL statement that is actually executed by the SQLite backend.

The only argument passed to the callback is the statement (as str) that is being executed. The return value of the callback is ignored. Note that the backend does not only run statements passed to the Cursor.execute methods. Other sources include the transaction management <sqlite3-controlling-transactions> of the !sqlite3 module and the execution of triggers defined in the current database.

Passing None as trace_callback will disable the trace callback.

Note

Exceptions raised in the trace callback are not propagated. As a development and debugging aid, use ~sqlite3.enable_callback_tracebacks to enable printing tracebacks from exceptions raised in the trace callback.

3.3

enable_load_extension(enabled, /)

Enable the SQLite engine to load SQLite extensions from shared libraries if enabled is True; else, disallow loading SQLite extensions. SQLite extensions can define new functions, aggregates or whole new virtual table implementations. One well-known extension is the fulltext-search extension distributed with SQLite.

Note

The !sqlite3 module is not built with loadable extension support by default, because some platforms (notably macOS) have SQLite libraries which are compiled without this feature. To get loadable extension support, you must pass the --enable-loadable-sqlite-extensions option to configure.

sqlite3.enable_load_extension connection,enabled sqlite3.Connection.enable_load_extension

3.2

3.10 Added the sqlite3.enable_load_extension auditing event.

../includes/sqlite3/load_extension.py

load_extension(path, /)

Load an SQLite extension from a shared library located at path. Enable extension loading with enable_load_extension before calling this method.

sqlite3.load_extension connection,path sqlite3.Connection.load_extension

3.2

3.10 Added the sqlite3.load_extension auditing event.

iterdump

Return an iterator to dump the database as SQL source code. Useful when saving an in-memory database for later restoration. Similar to the .dump command in the sqlite3 shell.

Example:

# Convert file example.db to SQL dump file dump.sql con = sqlite3.connect('example.db') with open('dump.sql', 'w') as f: for line in con.iterdump(): f.write('%sn' % line) con.close()

backup(target, *, pages=-1, progress=None, name="main", sleep=0.250)

Create a backup of an SQLite database.

Works even if the database is being accessed by other clients or concurrently by the same connection.

param Connection target

The database connection to save the backup to.

param int pages

The number of pages to copy at a time. If equal to or less than 0, the entire database is copied in a single step. Defaults to -1.

param progress

If set to a callable, it is invoked with three integer arguments for every backup iteration: the status of the last iteration, the remaining number of pages still to be copied, and the total number of pages. Defaults to None.

type progress

callback | None

param str name

The name of the database to back up. Either "main" (the default) for the main database, "temp" for the temporary database, or the name of a custom database as attached using the ATTACH DATABASE SQL statement.

param float sleep

The number of seconds to sleep between successive attempts to back up remaining pages.

Example 1, copy an existing database into another:

def progress(status, remaining, total):

print(f'Copied {total-remaining} of {total} pages...')

src = sqlite3.connect('example.db') dst = sqlite3.connect('backup.db') with dst: src.backup(dst, pages=1, progress=progress) dst.close() src.close()

Copied 0 of 0 pages...

Example 2, copy an existing database into a transient copy:

src = sqlite3.connect('example.db') dst = sqlite3.connect(':memory:') src.backup(dst)

3.7

getlimit(category, /)

Get a connection runtime limit.

param int category

The SQLite limit category to be queried.

rtype

int

raises ProgrammingError

If category is not recognised by the underlying SQLite library.

Example, query the maximum length of an SQL statement for Connection con (the default is 1000000000):

sqlite3.limits

import sqlite3 con = sqlite3.connect(":memory:") con.setlimit(sqlite3.SQLITE_LIMIT_SQL_LENGTH, 1_000_000_000) con.setlimit(sqlite3.SQLITE_LIMIT_ATTACHED, 10)

sqlite3.limits

>>> con.getlimit(sqlite3.SQLITE_LIMIT_SQL_LENGTH) 1000000000

3.11

setlimit(category, limit, /)

Set a connection runtime limit. Attempts to increase a limit above its hard upper bound are silently truncated to the hard upper bound. Regardless of whether or not the limit was changed, the prior value of the limit is returned.

param int category

The SQLite limit category to be set.

param int limit

The value of the new limit. If negative, the current limit is unchanged.

rtype

int

raises ProgrammingError

If category is not recognised by the underlying SQLite library.

Example, limit the number of attached databases to 1 for Connection con (the default limit is 10):

sqlite3.limits

>>> con.setlimit(sqlite3.SQLITE_LIMIT_ATTACHED, 1) 10 >>> con.getlimit(sqlite3.SQLITE_LIMIT_ATTACHED) 1

3.11

serialize(*, name="main")

Serialize a database into a bytes object. For an ordinary on-disk database file, the serialization is just a copy of the disk file. For an in-memory database or a "temp" database, the serialization is the same sequence of bytes which would be written to disk if that database were backed up to disk.

param str name

The database name to be serialized. Defaults to "main".

rtype

bytes

Note

This method is only available if the underlying SQLite library has the serialize API.

3.11

deserialize(data, /, *, name="main")

Deserialize a serialized <serialize> database into a Connection. This method causes the database connection to disconnect from database name, and reopen name as an in-memory database based on the serialization contained in data.

param bytes data

A serialized database.

param str name

The database name to deserialize into. Defaults to "main".

raises OperationalError

If the database connection is currently involved in a read transaction or a backup operation.

raises DatabaseError

If data does not contain a valid SQLite database.

raises OverflowError

If len(data) <len> is larger than 2**63 - 1.

Note

This method is only available if the underlying SQLite library has the deserialize API.

3.11

Cursor objects

A Cursor object represents a database cursor which is used to execute SQL statements, and manage the context of a fetch operation. Cursors are created using Connection.cursor, or by using any of the connection shortcut methods <sqlite3-connection-shortcuts>.

Cursor objects are iterators <iterator>, meaning that if you ~Cursor.execute a SELECT query, you can simply iterate over the cursor to fetch the resulting rows:

sqlite3.cursor

import sqlite3 con = sqlite3.connect(":memory:", isolation_level=None) cur = con.execute("CREATE TABLE data(t)") cur.execute("INSERT INTO data VALUES(1)")

sqlite3.cursor

for row in cur.execute("SELECT t FROM data"):

print(row)

sqlite3.cursor

(1,)

A Cursor instance has the following attributes and methods.

single: ? (question mark); in SQL statements

single: : (colon); in SQL statements

execute(sql, parameters=(), /)

Execute SQL statement sql. Bind values to the statement using placeholders <sqlite3-placeholders> that map to the sequence or dict parameters.

execute will only execute a single SQL statement. If you try to execute more than one statement with it, it will raise a ProgrammingError. Use executescript if you want to execute multiple SQL statements with one call.

If ~Connection.isolation_level is not None, sql is an INSERT, UPDATE, DELETE, or REPLACE statement, and there is no open transaction, a transaction is implicitly opened before executing sql.

executemany(sql, parameters, /)

Execute parameterized <sqlite3-placeholders> SQL statement sql against all parameter sequences or mappings found in the sequence parameters. It is also possible to use an iterator yielding parameters instead of a sequence. Uses the same implicit transaction handling as ~Cursor.execute.

Example:

sqlite3.cursor

rows = [

("row1",), ("row2",),

] # cur is an sqlite3.Cursor object cur.executemany("INSERT INTO data VALUES(?)", rows)

executescript(sql_script, /)

Execute the SQL statements in sql_script. If there is a pending transaction, an implicit COMMIT statement is executed first. No other implicit transaction control is performed; any transaction control must be added to sql_script.

sql_script must be a string <str>.

Example:

sqlite3.cursor

# cur is an sqlite3.Cursor object cur.executescript(""" BEGIN; CREATE TABLE person(firstname, lastname, age); CREATE TABLE book(title, author, published); CREATE TABLE publisher(name, address); COMMIT; """)

fetchone()

Return the next row of a query result set as a tuple. Return None if no more data is available.

fetchmany(size=cursor.arraysize)

Return the next set of rows of a query result as a list. Return an empty list if no more rows are available.

The number of rows to fetch per call is specified by the size parameter. If size is not given, arraysize determines the number of rows to be fetched. If fewer than size rows are available, as many rows as are available are returned.

Note there are performance considerations involved with the size parameter. For optimal performance, it is usually best to use the arraysize attribute. If the size parameter is used, then it is best for it to retain the same value from one fetchmany call to the next.

fetchall()

Return all (remaining) rows of a query result as a list. Return an empty list if no rows are available. Note that the arraysize attribute can affect the performance of this operation.

close()

Close the cursor now (rather than whenever __del__ is called).

The cursor will be unusable from this point forward; a ProgrammingError exception will be raised if any operation is attempted with the cursor.

setinputsizes(sizes, /)

Required by the DB-API. Does nothing in !sqlite3.

setoutputsize(size, column=None, /)

Required by the DB-API. Does nothing in !sqlite3.

rowcount

Read-only attribute that provides the number of modified rows for INSERT, UPDATE, DELETE, and REPLACE statements; is -1 for other statements, including CTE (Common Table Expression) queries. It is only updated by the execute and executemany methods.

lastrowid

Read-only attribute that provides the row id of the last inserted row. It is only updated after successful INSERT or REPLACE statements using the execute method. For other statements, after executemany or executescript, or if the insertion failed, the value of lastrowid is left unchanged. The initial value of lastrowid is None.

Note

Inserts into WITHOUT ROWID tables are not recorded.

3.6 Added support for the REPLACE statement.

arraysize

Read/write attribute that controls the number of rows returned by fetchmany. The default value is 1 which means a single row would be fetched per call.

description

Read-only attribute that provides the column names of the last query. To remain compatible with the Python DB API, it returns a 7-tuple for each column where the last six items of each tuple are None.

It is set for SELECT statements without any matching rows as well.

connection

Read-only attribute that provides the SQLite database Connection belonging to the cursor. A Cursor object created by calling con.cursor() <Connection.cursor> will have a connection attribute that refers to con:

>>> con = sqlite3.connect(":memory:") >>> cur = con.cursor() >>> cur.connection == con True

Row objects

A !Row instance serves as a highly optimized ~Connection.row_factory for Connection objects. It supports iteration, equality testing, len, and mapping access by column name and index.

Two row objects compare equal if have equal columns and equal members.

keys

Return a list of column names as strings <str>. Immediately after a query, it is the first member of each tuple in Cursor.description.

3.5 Added support of slicing.

Example:

>>> con = sqlite3.connect(":memory:") >>> con.row_factory = sqlite3.Row >>> res = con.execute("SELECT 'Earth' AS name, 6378 AS radius") >>> row = res.fetchone() >>> row.keys() ['name', 'radius'] >>> row[0], row["name"] # Access by index and name. ('Earth', 'Earth') >>> row["RADIUS"] # Column names are case-insensitive. 6378

Blob objects

3.11

A Blob instance is a file-like object that can read and write data in an SQLite BLOB (Binary Large OBject). Call len(blob) <len> to get the size (number of bytes) of the blob. Use indices and slices <slice> for direct access to the blob data.

Use the Blob as a context manager to ensure that the blob handle is closed after use.

../includes/sqlite3/blob.py

close()

Close the blob.

The blob will be unusable from this point onward. An ~sqlite3.Error (or subclass) exception will be raised if any further operation is attempted with the blob.

read(length=-1, /)

Read length bytes of data from the blob at the current offset position. If the end of the blob is reached, the data up to EOF (End of File) will be returned. When length is not specified, or is negative, ~Blob.read will read until the end of the blob.

write(data, /)

Write data to the blob at the current offset. This function cannot change the blob length. Writing beyond the end of the blob will raise ValueError.

tell()

Return the current access position of the blob.

seek(offset, origin=os.SEEK_SET, /)

Set the current access position of the blob to offset. The origin argument defaults to os.SEEK_SET (absolute blob positioning). Other values for origin are os.SEEK_CUR (seek relative to the current position) and os.SEEK_END (seek relative to the blob’s end).

PrepareProtocol objects

The PrepareProtocol type's single purpose is to act as a 246 style adaption protocol for objects that can adapt themselves <sqlite3-conform> to native SQLite types <sqlite3-types>.

Exceptions

The exception hierarchy is defined by the DB-API 2.0 (249).

Warning

This exception is not currently raised by the !sqlite3 module, but may be raised by applications using !sqlite3, for example if a user-defined function truncates data while inserting. Warning is a subclass of Exception.

Error

The base class of the other exceptions in this module. Use this to catch all errors with one single except statement. Error is a subclass of Exception.

If the exception originated from within the SQLite library, the following two attributes are added to the exception:

sqlite_errorcode

The numeric error code from the SQLite API

3.11

sqlite_errorname

The symbolic name of the numeric error code from the SQLite API

3.11

InterfaceError

Exception raised for misuse of the low-level SQLite C API. In other words, if this exception is raised, it probably indicates a bug in the !sqlite3 module. InterfaceError is a subclass of Error.

DatabaseError

Exception raised for errors that are related to the database. This serves as the base exception for several types of database errors. It is only raised implicitly through the specialised subclasses. DatabaseError is a subclass of Error.

DataError

Exception raised for errors caused by problems with the processed data, like numeric values out of range, and strings which are too long. DataError is a subclass of DatabaseError.

OperationalError

Exception raised for errors that are related to the database's operation, and not necessarily under the control of the programmer. For example, the database path is not found, or a transaction could not be processed. OperationalError is a subclass of DatabaseError.

IntegrityError

Exception raised when the relational integrity of the database is affected, e.g. a foreign key check fails. It is a subclass of DatabaseError.

InternalError

Exception raised when SQLite encounters an internal error. If this is raised, it may indicate that there is a problem with the runtime SQLite library. InternalError is a subclass of DatabaseError.

ProgrammingError

Exception raised for !sqlite3 API programming errors, for example supplying the wrong number of bindings to a query, or trying to operate on a closed Connection. ProgrammingError is a subclass of DatabaseError.

NotSupportedError

Exception raised in case a method or database API is not supported by the underlying SQLite library. For example, setting deterministic to True in ~Connection.create_function, if the underlying SQLite library does not support deterministic functions. NotSupportedError is a subclass of DatabaseError.

SQLite and Python types

SQLite natively supports the following types: NULL, INTEGER, REAL, TEXT, BLOB.

The following Python types can thus be sent to SQLite without any problem:

Python type	SQLite type
None	NULL
int	INTEGER
float	REAL
str	TEXT
bytes	BLOB

This is how SQLite types are converted to Python types by default:

SQLite type	Python type
NULL	None
INTEGER	int
REAL	float
TEXT	depends on ~Connection.text_factory, str by default
BLOB	bytes

The type system of the !sqlite3 module is extensible in two ways: you can store additional Python types in an SQLite database via object adapters <sqlite3-adapters>, and you can let the !sqlite3 module convert SQLite types to Python types via converters <sqlite3-converters>.

Default adapters and converters

There are default adapters for the date and datetime types in the datetime module. They will be sent as ISO dates/ISO timestamps to SQLite.

The default converters are registered under the name "date" for datetime.date and under the name "timestamp" for datetime.datetime.

This way, you can use date/timestamps from Python without any additional fiddling in most cases. The format of the adapters is also compatible with the experimental SQLite date/time functions.

The following example demonstrates this.

../includes/sqlite3/pysqlite_datetime.py

If a timestamp stored in SQLite has a fractional part longer than 6 numbers, its value will be truncated to microsecond precision by the timestamp converter.

Note

The default "timestamp" converter ignores UTC offsets in the database and always returns a naive datetime.datetime object. To preserve UTC offsets in timestamps, either leave converters disabled, or register an offset-aware converter with register_converter.

How-to guides

How to use placeholders to bind values in SQL queries

SQL operations usually need to use values from Python variables. However, beware of using Python's string operations to assemble queries, as they are vulnerable to SQL injection attacks (see the xkcd webcomic for a humorous example of what can go wrong):

# Never do this -- insecure!
symbol = 'RHAT'
cur.execute("SELECT * FROM stocks WHERE symbol = '%s'" % symbol)

Instead, use the DB-API's parameter substitution. To insert a variable into a query string, use a placeholder in the string, and substitute the actual values into the query by providing them as a tuple of values to the second argument of the cursor's ~Cursor.execute method. An SQL statement may use one of two kinds of placeholders: question marks (qmark style) or named placeholders (named style). For the qmark style, parameters must be a sequence <sequence>. For the named style, it can be either a sequence <sequence> or dict instance. The length of the sequence <sequence> must match the number of placeholders, or a ProgrammingError is raised. If a dict is given, it must contain keys for all named parameters. Any extra items are ignored. Here's an example of both styles:

../includes/sqlite3/execute_1.py

How to adapt custom Python types to SQLite values

SQLite supports only a limited set of data types natively. To store custom Python types in SQLite databases, adapt them to one of the Python types SQLite natively understands <sqlite3-types>.

There are two ways to adapt Python objects to SQLite types: letting your object adapt itself, or using an adapter callable. The latter will take precedence above the former. For a library that exports a custom type, it may make sense to enable that type to adapt itself. As an application developer, it may make more sense to take direct control by registering custom adapter functions.

How to write adaptable objects

Suppose we have a !Point class that represents a pair of coordinates, x and y, in a Cartesian coordinate system. The coordinate pair will be stored as a text string in the database, using a semicolon to separate the coordinates. This can be implemented by adding a __conform__(self, protocol) method which returns the adapted value. The object passed to protocol will be of type PrepareProtocol.

../includes/sqlite3/adapter_point_1.py

How to register adapter callables

The other possibility is to create a function that converts the Python object to an SQLite-compatible type. This function can then be registered using register_adapter.

../includes/sqlite3/adapter_point_2.py

How to convert SQLite values to custom Python types

Writing an adapter lets you convert from custom Python types to SQLite values. To be able to convert from SQLite values to custom Python types, we use converters.

Let's go back to the !Point class. We stored the x and y coordinates separated via semicolons as strings in SQLite.

First, we'll define a converter function that accepts the string as a parameter and constructs a !Point object from it.

Note

Converter functions are always passed a bytes object, no matter the underlying SQLite data type.

def convert_point(s):

x, y = map(float, s.split(b";")) return Point(x, y)

We now need to tell !sqlite3 when it should convert a given SQLite value. This is done when connecting to a database, using the detect_types parameter of connect. There are three options:

• Implicit: set detect_types to PARSE_DECLTYPES
• Explicit: set detect_types to PARSE_COLNAMES
• Both: set detect_types to sqlite3.PARSE_DECLTYPES | sqlite3.PARSE_COLNAMES. Column names take precedence over declared types.

The following example illustrates the implicit and explicit approaches:

../includes/sqlite3/converter_point.py

Adapter and converter recipes

This section shows recipes for common adapters and converters.

import datetime import sqlite3

def adapt_date_iso(val):

"""Adapt datetime.date to ISO 8601 date.""" return val.isoformat()

def adapt_datetime_iso(val):

"""Adapt datetime.datetime to timezone-naive ISO 8601 date.""" return val.isoformat()

def adapt_datetime_epoch(val):

"""Adapt datetime.datetime to Unix timestamp.""" return int(val.timestamp())

sqlite3.register_adapter(datetime.date, adapt_date_iso) sqlite3.register_adapter(datetime.datetime, adapt_datetime_iso) sqlite3.register_adapter(datetime.datetime, adapt_datetime_epoch)

def convert_date(val):

"""Convert ISO 8601 date to datetime.date object.""" return datetime.date.fromisoformat(val)

def convert_datetime(val):

"""Convert ISO 8601 datetime to datetime.datetime object.""" return datetime.datetime.fromisoformat(val)

def convert_timestamp(val):

"""Convert Unix epoch timestamp to datetime.datetime object.""" return datetime.datetime.fromtimestamp(val)

sqlite3.register_converter("date", convert_date) sqlite3.register_converter("datetime", convert_datetime) sqlite3.register_converter("timestamp", convert_timestamp)

How to use connection shortcut methods

Using the ~Connection.execute, ~Connection.executemany, and ~Connection.executescript methods of the Connection class, your code can be written more concisely because you don't have to create the (often superfluous) Cursor objects explicitly. Instead, the Cursor objects are created implicitly and these shortcut methods return the cursor objects. This way, you can execute a SELECT statement and iterate over it directly using only a single call on the Connection object.

../includes/sqlite3/shortcut_methods.py

How to use the connection context manager

A Connection object can be used as a context manager that automatically commits or rolls back open transactions when leaving the body of the context manager. If the body of the with statement finishes without exceptions, the transaction is committed. If this commit fails, or if the body of the with statement raises an uncaught exception, the transaction is rolled back.

If there is no open transaction upon leaving the body of the with statement, the context manager is a no-op.

Note

The context manager neither implicitly opens a new transaction nor closes the connection.

../includes/sqlite3/ctx_manager.py

How to work with SQLite URIs

Some useful URI tricks include:

• Open a database in read-only mode:

>>> con = sqlite3.connect("file:tutorial.db?mode=ro", uri=True) >>> con.execute("CREATE TABLE readonly(data)") Traceback (most recent call last): OperationalError: attempt to write a readonly database

• Do not implicitly create a new database file if it does not already exist; will raise ~sqlite3.OperationalError if unable to create a new file:

>>> con = sqlite3.connect("file:nosuchdb.db?mode=rw", uri=True) Traceback (most recent call last): OperationalError: unable to open database file

• Create a shared named in-memory database:

db = "file:mem1?mode=memory&cache=shared" con1 = sqlite3.connect(db, uri=True) con2 = sqlite3.connect(db, uri=True) with con1: con1.execute("CREATE TABLE shared(data)") con1.execute("INSERT INTO shared VALUES(28)") res = con2.execute("SELECT data FROM shared") assert res.fetchone() == (28,)

More information about this feature, including a list of parameters, can be found in the SQLite URI documentation.

Explanation

Transaction control

The !sqlite3 module does not adhere to the transaction handling recommended by 249.

If the connection attribute ~Connection.isolation_level is not None, new transactions are implicitly opened before ~Cursor.execute and ~Cursor.executemany executes INSERT, UPDATE, DELETE, or REPLACE statements. Use the ~Connection.commit and ~Connection.rollback methods to respectively commit and roll back pending transactions. You can choose the underlying SQLite transaction behaviour — that is, whether and what type of BEGIN statements !sqlite3 implicitly executes – via the ~Connection.isolation_level attribute.

If ~Connection.isolation_level is set to None, no transactions are implicitly opened at all. This leaves the underlying SQLite library in autocommit mode, but also allows the user to perform their own transaction handling using explicit SQL statements. The underlying SQLite library autocommit mode can be queried using the ~Connection.in_transaction attribute.

The ~Cursor.executescript method implicitly commits any pending transaction before execution of the given SQL script, regardless of the value of ~Connection.isolation_level.

3.6 !sqlite3 used to implicitly commit an open transaction before DDL statements. This is no longer the case.