sqlite3 — DB-API 2.0 interface for SQLite databases

Source code: Lib/sqlite3/


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 PEP 249, and requires SQLite 3.7.15 or newer.

To use the module, start by creating a Connection object that represents the database. Here the data will be stored in the example.db file:

import sqlite3
con = sqlite3.connect('example.db')

The special path name :memory: can be provided to create a temporary database in RAM.

Once a Connection has been established, create a Cursor object and call its execute() method to perform SQL commands:

cur = con.cursor()

# Create table
cur.execute('''CREATE TABLE stocks
               (date text, trans text, symbol text, qty real, price real)''')

# Insert a row of data
cur.execute("INSERT INTO stocks VALUES ('2006-01-05','BUY','RHAT',100,35.14)")

# Save (commit) the changes
con.commit()

# We can also close the connection if we are done with it.
# Just be sure any changes have been committed or they will be lost.
con.close()

The saved data is persistent: it can be reloaded in a subsequent session even after restarting the Python interpreter:

import sqlite3
con = sqlite3.connect('example.db')
cur = con.cursor()

To retrieve data after executing a SELECT statement, either treat the cursor as an iterator, call the cursor’s fetchone() method to retrieve a single matching row, or call fetchall() to get a list of the matching rows.

This example uses the iterator form:

>>> for row in cur.execute('SELECT * FROM stocks ORDER BY price'):
        print(row)

('2006-01-05', 'BUY', 'RHAT', 100, 35.14)
('2006-03-28', 'BUY', 'IBM', 1000, 45.0)
('2006-04-06', 'SELL', 'IBM', 500, 53.0)
('2006-04-05', 'BUY', 'MSFT', 1000, 72.0)

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 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. For the named style, it can be either a sequence or dict instance. The length of the 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:

import sqlite3

con = sqlite3.connect(":memory:")
cur = con.cursor()
cur.execute("create table lang (name, first_appeared)")

# This is the qmark style:
cur.execute("insert into lang values (?, ?)", ("C", 1972))

# The qmark style used with executemany():
lang_list = [
    ("Fortran", 1957),
    ("Python", 1991),
    ("Go", 2009),
]
cur.executemany("insert into lang values (?, ?)", lang_list)

# And this is the named style:
cur.execute("select * from lang where first_appeared=:year", {"year": 1972})
print(cur.fetchall())

con.close()

See also

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.

PEP 249 - Database API Specification 2.0

PEP written by Marc-André Lemburg.

Module functions and constants

sqlite3.apilevel

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

sqlite3.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.

sqlite3.version

The version number of this module, as a string. This is not the version of the SQLite library.

sqlite3.version_info

The version number of this module, as a tuple of integers. This is not the version of the SQLite library.

sqlite3.sqlite_version

The version number of the run-time SQLite library, as a string.

sqlite3.sqlite_version_info

The version number of the run-time SQLite library, as a tuple of integers.

sqlite3.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

Changed in version 3.11: Set threadsafety dynamically instead of hard-coding it to 1.

sqlite3.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.

sqlite3.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.

sqlite3.connect(database[, timeout, detect_types, isolation_level, check_same_thread, factory, cached_statements, uri])

Opens a connection to the SQLite database file database. By default returns a Connection object, unless a custom factory is given.

database is a path-like object giving the pathname (absolute or relative to the current working directory) of the database file to be opened. You can use ":memory:" to open a database connection to a database that resides in RAM instead of on disk.

When a database is accessed by multiple connections, and one of the processes modifies the database, the SQLite database is locked until that transaction is committed. The timeout parameter specifies how long the connection should wait for the lock to go away until raising an exception. The default for the timeout parameter is 5.0 (five seconds).

For the isolation_level parameter, please see the isolation_level property of Connection objects.

SQLite natively supports only the types TEXT, INTEGER, REAL, BLOB and NULL. If you want to use other types you must add support for them yourself. The detect_types parameter and using custom converters registered with the module-level register_converter() function allow you to easily do that.

detect_types defaults to 0 (type detection disabled). Set it to any combination (using |, bitwise or) of PARSE_DECLTYPES and PARSE_COLNAMES to enable type detection. 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. In such cases, the returned type is str.

By default, check_same_thread is True and only the creating thread may use the connection. If set False, the returned connection may be shared across multiple threads. When using multiple threads with the same connection writing operations should be serialized by the user to avoid data corruption.

By default, the sqlite3 module uses its Connection class for the connect call. You can, however, subclass the Connection class and make connect() use your class instead by providing your class for the factory parameter.

Consult the section SQLite and Python types of this manual for details.

The sqlite3 module internally uses a statement cache to avoid SQL parsing overhead. If you want to explicitly set the number of statements that are cached for the connection, you can set the cached_statements parameter. The currently implemented default is to cache 128 statements.

If uri is True, database is interpreted as a URI with a file path and an optional query string. The scheme part must be "file:". The path can be a relative or absolute file path. The query string allows us to pass parameters to SQLite. Some useful URI tricks include:

# Open a database in read-only mode.
con = sqlite3.connect("file:template.db?mode=ro", uri=True)

# Don't implicitly create a new database file if it does not already exist.
# Will raise sqlite3.OperationalError if unable to open a database file.
con = sqlite3.connect("file:nosuchdb.db?mode=rw", uri=True)

# Create a shared named in-memory database.
con1 = sqlite3.connect("file:mem1?mode=memory&cache=shared", uri=True)
con2 = sqlite3.connect("file:mem1?mode=memory&cache=shared", uri=True)
con1.executescript("create table t(t); insert into t values(28);")
rows = con2.execute("select * from t").fetchall()

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

Raises an auditing event sqlite3.connect with argument database.

Raises an auditing event sqlite3.connect/handle with argument connection_handle.

Changed in version 3.4: Added the uri parameter.

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

Changed in version 3.10: Added the sqlite3.connect/handle auditing event.

sqlite3.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.

sqlite3.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.complete_statement(statement)

Returns True if the string statement contains one or more complete SQL statements terminated by semicolons. It does not verify that the SQL is syntactically correct, only that there are no unclosed string literals and the statement is terminated by a semicolon.

This can be used to build a shell for SQLite, as in the following example:

# A minimal SQLite shell for experiments

import sqlite3

con = sqlite3.connect(":memory:")
con.isolation_level = None
cur = con.cursor()

buffer = ""

print("Enter your SQL commands to execute in sqlite3.")
print("Enter a blank line to exit.")

while True:
    line = input()
    if line == "":
        break
    buffer += line
    if sqlite3.complete_statement(buffer):
        try:
            buffer = buffer.strip()
            cur.execute(buffer)

            if buffer.lstrip().upper().startswith("SELECT"):
                print(cur.fetchall())
        except sqlite3.Error as e:
            err_msg = str(e)
            err_code = e.sqlite_errorcode
            err_name = e.sqlite_errorname
            print(f"{err_name} ({err_code}): {err_msg}")
        buffer = ""

con.close()
sqlite3.enable_callback_tracebacks(flag)

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 for an improved debug experience:

>>> import sqlite3
>>> sqlite3.enable_callback_tracebacks(True)
>>> cx = sqlite3.connect(":memory:")
>>> cx.set_trace_callback(lambda stmt: 5/0)
>>> cx.execute("select 1")
Exception ignored in: <function <lambda> at 0x10b4e3ee0>
Traceback (most recent call last):
  File "<stdin>", line 1, in <lambda>
ZeroDivisionError: division by zero
>>> import sys
>>> sys.unraisablehook = lambda unraisable: print(unraisable)
>>> cx.execute("select 1")
UnraisableHookArgs(exc_type=<class 'ZeroDivisionError'>, exc_value=ZeroDivisionError('division by zero'), exc_traceback=<traceback object at 0x10b559900>, err_msg=None, object=<function <lambda> at 0x10b4e3ee0>)
<sqlite3.Cursor object at 0x10b1fe840>

Connection Objects

class sqlite3.Connection

An SQLite database connection has the following attributes and methods:

isolation_level

Get or set the current default isolation level. None for autocommit mode or one of “DEFERRED”, “IMMEDIATE” or “EXCLUSIVE”. See section Controlling Transactions for a more detailed explanation.

in_transaction

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

New in version 3.2.

cursor(factory=Cursor)

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 the BLOB located in table name table, column name column, and row index row of database name. When readonly is True the blob is opened without write permissions. Trying to open a blob in a WITHOUT ROWID table will raise OperationalError.

Note

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

New in version 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 execute() on it with the given sql and parameters. Return the new cursor object.

executemany(sql[, parameters])

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

executescript(sql_script)

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

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

Creates a user-defined function that you can later use from within SQL statements under the function name name. narg is the number of parameters the function accepts (if narg is -1, the function may take any number of arguments), and func is a Python callable that is called as the SQL function. If deterministic is true, the created function is marked as deterministic, which allows SQLite to perform additional optimizations. This flag is supported by SQLite 3.8.3 or higher, NotSupportedError will be raised if used with older versions.

The function can return any of the types supported by SQLite: bytes, str, int, float and None.

Changed in version 3.8: The deterministic parameter was added.

Example:

import sqlite3
import hashlib

def md5sum(t):
    return hashlib.md5(t).hexdigest()

con = sqlite3.connect(":memory:")
con.create_function("md5", 1, md5sum)
cur = con.cursor()
cur.execute("select md5(?)", (b"foo",))
print(cur.fetchone()[0])

con.close()
create_aggregate(name, n_arg, aggregate_class)

Creates a user-defined aggregate function.

The aggregate class must implement a step method, which accepts the number of parameters n_arg (if n_arg is -1, the function may take any number of arguments), and a finalize method which will return the final result of the aggregate.

The finalize method can return any of the types supported by SQLite: bytes, str, int, float and None.

Example:

import sqlite3

class MySum:
    def __init__(self):
        self.count = 0

    def step(self, value):
        self.count += value

    def finalize(self):
        return self.count

con = sqlite3.connect(":memory:")
con.create_aggregate("mysum", 1, MySum)
cur = con.cursor()
cur.execute("create table test(i)")
cur.execute("insert into test(i) values (1)")
cur.execute("insert into test(i) values (2)")
cur.execute("select mysum(i) from test")
print(cur.fetchone()[0])

con.close()
create_window_function(name, num_params, aggregate_class, /)

Creates user-defined aggregate window function name.

aggregate_class must implement the following methods:

  • step: adds a row to the current window

  • value: returns the current value of the aggregate

  • inverse: removes a row from the current window

  • finalize: returns the final value of the aggregate

step and value accept num_params number of parameters, unless num_params is -1, in which case they may take any number of arguments. finalize and value can return any of the types supported by SQLite: bytes, str, int, float, and None. Call create_window_function() with aggregate_class set to None to clear window function name.

Aggregate window functions are supported by SQLite 3.25.0 and higher. NotSupportedError will be raised if used with older versions.

New in version 3.11.

Example:

# Example taken from https://www.sqlite.org/windowfunctions.html#udfwinfunc
import sqlite3


class WindowSumInt:
    def __init__(self):
        self.count = 0

    def step(self, value):
        """Adds a row to the current window."""
        self.count += value

    def value(self):
        """Returns the current value of the aggregate."""
        return self.count

    def inverse(self, value):
        """Removes a row from the current window."""
        self.count -= value

    def finalize(self):
        """Returns the final value of the aggregate.

        Any clean-up actions should be placed here.
        """
        return self.count


con = sqlite3.connect(":memory:")
cur = con.execute("create table test(x, y)")
values = [
    ("a", 4),
    ("b", 5),
    ("c", 3),
    ("d", 8),
    ("e", 1),
]
cur.executemany("insert into test values(?, ?)", values)
con.create_window_function("sumint", 1, WindowSumInt)
cur.execute("""
    select x, sumint(y) over (
        order by x rows between 1 preceding and 1 following
    ) as sum_y
    from test order by x
""")
print(cur.fetchall())
create_collation(name, callable)

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

  • 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:

import sqlite3

def collate_reverse(string1, string2):
    if string1 == string2:
        return 0
    elif string1 < string2:
        return 1
    else:
        return -1

con = sqlite3.connect(":memory:")
con.create_collation("reverse", collate_reverse)

cur = con.cursor()
cur.execute("create table test(x)")
cur.executemany("insert into test(x) values (?)", [("a",), ("b",)])
cur.execute("select x from test order by x collate reverse")
for row in cur:
    print(row)
con.close()

Remove a collation function by setting callable to None.

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

interrupt()

You can call this method from a different thread to abort any queries that might be executing on the connection. The query will then abort and the caller will get an exception.

set_authorizer(authorizer_callback)

This routine registers a callback. The callback is invoked for each attempt to access a column of a table in the database. The callback should return SQLITE_OK if access is allowed, SQLITE_DENY if the entire SQL statement should be aborted with an error and SQLITE_IGNORE if the column should be treated as a NULL value. These constants are available in the sqlite3 module.

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.

Changed in version 3.11: Added support for disabling the authorizer using None.

set_progress_handler(progress_handler, n)

This routine registers a callback. The callback is 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)

Registers trace_callback to be called 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 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 enable_callback_tracebacks() to enable printing tracebacks from exceptions raised in the trace callback.

New in version 3.3.

enable_load_extension(enabled)

This routine allows/disallows the SQLite engine to load SQLite extensions from shared libraries. 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.

Loadable extensions are disabled by default. See 1.

Raises an auditing event sqlite3.enable_load_extension with arguments connection, enabled.

New in version 3.2.

Changed in version 3.10: Added the sqlite3.enable_load_extension auditing event.

import sqlite3

con = sqlite3.connect(":memory:")

# enable extension loading
con.enable_load_extension(True)

# Load the fulltext search extension
con.execute("select load_extension('./fts3.so')")

# alternatively you can load the extension using an API call:
# con.load_extension("./fts3.so")

# disable extension loading again
con.enable_load_extension(False)

# example from SQLite wiki
con.execute("create virtual table recipe using fts3(name, ingredients)")
con.executescript("""
    insert into recipe (name, ingredients) values ('broccoli stew', 'broccoli peppers cheese tomatoes');
    insert into recipe (name, ingredients) values ('pumpkin stew', 'pumpkin onions garlic celery');
    insert into recipe (name, ingredients) values ('broccoli pie', 'broccoli cheese onions flour');
    insert into recipe (name, ingredients) values ('pumpkin pie', 'pumpkin sugar flour butter');
    """)
for row in con.execute("select rowid, name, ingredients from recipe where name match 'pie'"):
    print(row)

con.close()
load_extension(path)

This routine loads an SQLite extension from a shared library. You have to enable extension loading with enable_load_extension() before you can use this routine.

Loadable extensions are disabled by default. See 1.

Raises an auditing event sqlite3.load_extension with arguments connection, path.

New in version 3.2.

Changed in version 3.10: Added the sqlite3.load_extension auditing event.

row_factory

You can change this attribute to a callable that accepts the cursor and the original row as a tuple and will return the real result row. This way, you can implement more advanced ways of returning results, such as returning an object that can also access columns by name.

Example:

import sqlite3

def dict_factory(cursor, row):
    d = {}
    for idx, col in enumerate(cursor.description):
        d[col[0]] = row[idx]
    return d

con = sqlite3.connect(":memory:")
con.row_factory = dict_factory
cur = con.cursor()
cur.execute("select 1 as a")
print(cur.fetchone()["a"])

con.close()

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

Using this attribute you can control what objects are returned for the TEXT data type. By default, this attribute is set to str and the sqlite3 module will return str objects for TEXT. If you want to return bytes instead, you can set it to bytes.

You can also set it to any other callable that accepts a single bytestring parameter and returns the resulting object.

See the following example code for illustration:

import sqlite3

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

AUSTRIA = "Österreich"

# by default, rows are returned as str
cur.execute("select ?", (AUSTRIA,))
row = cur.fetchone()
assert row[0] == AUSTRIA

# but we can make sqlite3 always return bytestrings ...
con.text_factory = bytes
cur.execute("select ?", (AUSTRIA,))
row = cur.fetchone()
assert type(row[0]) is bytes
# the bytestrings will be encoded in UTF-8, unless you stored garbage in the
# database ...
assert row[0] == AUSTRIA.encode("utf-8")

# we can also implement a custom text_factory ...
# here we implement one that appends "foo" to all strings
con.text_factory = lambda x: x.decode("utf-8") + "foo"
cur.execute("select ?", ("bar",))
row = cur.fetchone()
assert row[0] == "barfoo"

con.close()
total_changes

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

iterdump()

Returns an iterator to dump the database in an SQL text format. Useful when saving an in-memory database for later restoration. This function provides the same capabilities as the .dump command in the sqlite3 shell.

Example:

# Convert file existing_db.db to SQL dump file dump.sql
import sqlite3

con = sqlite3.connect('existing_db.db')
with open('dump.sql', 'w') as f:
    for line in con.iterdump():
        f.write('%s\n' % line)
con.close()
backup(target, *, pages=- 1, progress=None, name='main', sleep=0.250)

This method makes a backup of an SQLite database even while it’s being accessed by other clients, or concurrently by the same connection. The copy will be written into the mandatory argument target, that must be another Connection instance.

By default, or when pages is either 0 or a negative integer, the entire database is copied in a single step; otherwise the method performs a loop copying up to pages pages at a time.

If progress is specified, it must either be None or a callable object that will be executed at each iteration with three integer arguments, respectively the status of the last iteration, the remaining number of pages still to be copied and the total number of pages.

The name argument specifies the database name that will be copied: it must be a string containing either "main", the default, to indicate the main database, "temp" to indicate the temporary database or the name specified after the AS keyword in an ATTACH DATABASE statement for an attached database.

The sleep argument specifies the number of seconds to sleep by between successive attempts to backup remaining pages, can be specified either as an integer or a floating point value.

Example 1, copy an existing database into another:

import sqlite3

def progress(status, remaining, total):
    print(f'Copied {total-remaining} of {total} pages...')

con = sqlite3.connect('existing_db.db')
bck = sqlite3.connect('backup.db')
with bck:
    con.backup(bck, pages=1, progress=progress)
bck.close()
con.close()

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

import sqlite3

source = sqlite3.connect('existing_db.db')
dest = sqlite3.connect(':memory:')
source.backup(dest)

New in version 3.7.

getlimit(category, /)

Get a connection run-time limit. category is the limit category to be queried.

Example, query the maximum length of an SQL statement:

import sqlite3
con = sqlite3.connect(":memory:")
lim = con.getlimit(sqlite3.SQLITE_LIMIT_SQL_LENGTH)
print(f"SQLITE_LIMIT_SQL_LENGTH={lim}")

New in version 3.11.

setlimit(category, limit, /)

Set a connection run-time limit. category is the limit category to be set. limit is the new limit. If the new limit is a negative number, the limit is unchanged.

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.

Example, limit the number of attached databases to 1:

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

New in version 3.11.

serialize(*, name='main')

This method serializes 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.

name is the database to be serialized, and defaults to the main database.

Note

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

New in version 3.11.

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

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. Deserialization will raise OperationalError if the database connection is currently involved in a read transaction or a backup operation. OverflowError will be raised if len(data) is larger than 2**63 - 1, and DatabaseError will be raised if data does not contain a valid SQLite database.

Note

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

New in version 3.11.

Cursor Objects

class sqlite3.Cursor

A Cursor instance has the following attributes and methods.

execute(sql[, parameters])

Executes an SQL statement. Values may be bound to the statement using placeholders.

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.

executemany(sql, seq_of_parameters)

Executes a parameterized SQL command against all parameter sequences or mappings found in the sequence seq_of_parameters. The sqlite3 module also allows using an iterator yielding parameters instead of a sequence.

import sqlite3

class IterChars:
    def __init__(self):
        self.count = ord('a')

    def __iter__(self):
        return self

    def __next__(self):
        if self.count > ord('z'):
            raise StopIteration
        self.count += 1
        return (chr(self.count - 1),) # this is a 1-tuple

con = sqlite3.connect(":memory:")
cur = con.cursor()
cur.execute("create table characters(c)")

theIter = IterChars()
cur.executemany("insert into characters(c) values (?)", theIter)

cur.execute("select c from characters")
print(cur.fetchall())

con.close()

Here’s a shorter example using a generator:

import sqlite3
import string

def char_generator():
    for c in string.ascii_lowercase:
        yield (c,)

con = sqlite3.connect(":memory:")
cur = con.cursor()
cur.execute("create table characters(c)")

cur.executemany("insert into characters(c) values (?)", char_generator())

cur.execute("select c from characters")
print(cur.fetchall())

con.close()
executescript(sql_script)

This is a nonstandard convenience method for executing multiple SQL statements at once. It issues a COMMIT statement first, then executes the SQL script it gets as a parameter. This method disregards isolation_level; any transaction control must be added to sql_script.

sql_script can be an instance of str.

Example:

import sqlite3

con = sqlite3.connect(":memory:")
cur = con.cursor()
cur.executescript("""
    create table person(
        firstname,
        lastname,
        age
    );

    create table book(
        title,
        author,
        published
    );

    insert into book(title, author, published)
    values (
        'Dirk Gently''s Holistic Detective Agency',
        'Douglas Adams',
        1987
    );
    """)
con.close()
fetchone()

Fetches the next row of a query result set, returning a single sequence, or None when no more data is available.

fetchmany(size=cursor.arraysize)

Fetches the next set of rows of a query result, returning a list. An empty list is returned when no more rows are available.

The number of rows to fetch per call is specified by the size parameter. If it is not given, the cursor’s arraysize determines the number of rows to be fetched. The method should try to fetch as many rows as indicated by the size parameter. If this is not possible due to the specified number of rows not being available, fewer rows may be 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()

Fetches all (remaining) rows of a query result, returning a list. Note that the cursor’s arraysize attribute can affect the performance of this operation. An empty list is returned when no rows are available.

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])

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

rowcount

Although the Cursor class of the sqlite3 module implements this attribute, the database engine’s own support for the determination of “rows affected”/”rows selected” is quirky.

For executemany() statements, the number of modifications are summed up into rowcount.

As required by the Python DB API Spec, the rowcount attribute “is -1 in case no executeXX() has been performed on the cursor or the rowcount of the last operation is not determinable by the interface”. This includes SELECT statements because we cannot determine the number of rows a query produced until all rows were fetched.

lastrowid

This read-only attribute 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.

Changed in version 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

This read-only attribute 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

This read-only attribute provides the SQLite database Connection used by the Cursor object. A Cursor object created by calling con.cursor() will have a connection attribute that refers to con:

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

Row Objects

class sqlite3.Row

A Row instance serves as a highly optimized row_factory for Connection objects. It tries to mimic a tuple in most of its features.

It supports mapping access by column name and index, iteration, representation, equality testing and len().

If two Row objects have exactly the same columns and their members are equal, they compare equal.

keys()

This method returns a list of column names. Immediately after a query, it is the first member of each tuple in Cursor.description.

Changed in version 3.5: Added support of slicing.

Let’s assume we initialize a table as in the example given above:

con = sqlite3.connect(":memory:")
cur = con.cursor()
cur.execute('''create table stocks
(date text, trans text, symbol text,
 qty real, price real)''')
cur.execute("""insert into stocks
            values ('2006-01-05','BUY','RHAT',100,35.14)""")
con.commit()
cur.close()

Now we plug Row in:

>>> con.row_factory = sqlite3.Row
>>> cur = con.cursor()
>>> cur.execute('select * from stocks')
<sqlite3.Cursor object at 0x7f4e7dd8fa80>
>>> r = cur.fetchone()
>>> type(r)
<class 'sqlite3.Row'>
>>> tuple(r)
('2006-01-05', 'BUY', 'RHAT', 100.0, 35.14)
>>> len(r)
5
>>> r[2]
'RHAT'
>>> r.keys()
['date', 'trans', 'symbol', 'qty', 'price']
>>> r['qty']
100.0
>>> for member in r:
...     print(member)
...
2006-01-05
BUY
RHAT
100.0
35.14

Blob Objects

New in version 3.11.

class sqlite3.Blob

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

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

import sqlite3

con = sqlite3.connect(":memory:")
con.execute("create table test(blob_col blob)")
con.execute("insert into test(blob_col) values (zeroblob(13))")

# Write to our blob, using two write operations:
with con.blobopen("test", "blob_col", 1) as blob:
    blob.write(b"hello, ")
    blob.write(b"world.")
    # Modify the first and last bytes of our blob
    blob[0] = ord("H")
    blob[-1] = ord("!")

# Read the contents of our blob
with con.blobopen("test", "blob_col", 1) as blob:
    greeting = blob.read()

print(greeting)  # outputs "b'Hello, world!'"
close()

Close the blob.

The blob will be unusable from this point onward. An 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 will be returned. When length is not specified, or is negative, 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).

Exceptions

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

exception sqlite3.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.

exception sqlite3.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.

sqlite_errorcode

The numeric error code from the SQLite API

New in version 3.11.

sqlite_errorname

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

New in version 3.11.

exception sqlite3.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.

exception sqlite3.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.

exception sqlite3.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.

exception sqlite3.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.

exception sqlite3.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.

exception sqlite3.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.

exception sqlite3.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.

exception sqlite3.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 create_function(), if the underlying SQLite library does not support deterministic functions. NotSupportedError is a subclass of DatabaseError.

SQLite and Python types

Introduction

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 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 adaptation, and you can let the sqlite3 module convert SQLite types to different Python types via converters.

Using adapters to store custom Python types in SQLite databases

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.

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.

Letting your object adapt itself

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.

import sqlite3

class Point:
    def __init__(self, x, y):
        self.x, self.y = x, y

    def __conform__(self, protocol):
        if protocol is sqlite3.PrepareProtocol:
            return "%f;%f" % (self.x, self.y)

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

p = Point(4.0, -3.2)
cur.execute("select ?", (p,))
print(cur.fetchone()[0])

con.close()

Registering an adapter callable

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().

import sqlite3

class Point:
    def __init__(self, x, y):
        self.x, self.y = x, y

def adapt_point(point):
    return "%f;%f" % (point.x, point.y)

sqlite3.register_adapter(Point, adapt_point)

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

p = Point(4.0, -3.2)
cur.execute("select ?", (p,))
print(cur.fetchone()[0])

con.close()

Converting 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. Colum names take precedence over declared types.

The following example illustrates the implicit and explicit approaches:

import sqlite3

class Point:
    def __init__(self, x, y):
        self.x, self.y = x, y

    def __repr__(self):
        return f"Point({self.x}, {self.y})"

def adapt_point(point):
    return f"{point.x};{point.y}".encode("utf-8")

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

# Register the adapter and converter
sqlite3.register_adapter(Point, adapt_point)
sqlite3.register_converter("point", convert_point)

# 1) Parse using declared types
p = Point(4.0, -3.2)
con = sqlite3.connect(":memory:", detect_types=sqlite3.PARSE_DECLTYPES)
cur = con.execute("create table test(p point)")

cur.execute("insert into test(p) values (?)", (p,))
cur.execute("select p from test")
print("with declared types:", cur.fetchone()[0])
cur.close()
con.close()

# 2) Parse using column names
con = sqlite3.connect(":memory:", detect_types=sqlite3.PARSE_COLNAMES)
cur = con.execute("create table test(p)")

cur.execute("insert into test(p) values (?)", (p,))
cur.execute('select p as "p [point]" from test')
print("with column names:", cur.fetchone()[0])
cur.close()
con.close()

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.

import sqlite3
import datetime

con = sqlite3.connect(":memory:", detect_types=sqlite3.PARSE_DECLTYPES|sqlite3.PARSE_COLNAMES)
cur = con.cursor()
cur.execute("create table test(d date, ts timestamp)")

today = datetime.date.today()
now = datetime.datetime.now()

cur.execute("insert into test(d, ts) values (?, ?)", (today, now))
cur.execute("select d, ts from test")
row = cur.fetchone()
print(today, "=>", row[0], type(row[0]))
print(now, "=>", row[1], type(row[1]))

cur.execute('select current_date as "d [date]", current_timestamp as "ts [timestamp]"')
row = cur.fetchone()
print("current_date", row[0], type(row[0]))
print("current_timestamp", row[1], type(row[1]))

con.close()

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().

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)

Controlling Transactions

The underlying sqlite3 library operates in autocommit mode by default, but the Python sqlite3 module by default does not.

autocommit mode means that statements that modify the database take effect immediately. A BEGIN or SAVEPOINT statement disables autocommit mode, and a COMMIT, a ROLLBACK, or a RELEASE that ends the outermost transaction, turns autocommit mode back on.

The Python sqlite3 module by default issues a BEGIN statement implicitly before a Data Modification Language (DML) statement (i.e. INSERT/UPDATE/DELETE/REPLACE).

You can control which kind of BEGIN statements sqlite3 implicitly executes via the isolation_level parameter to the connect() call, or via the isolation_level property of connections. If you specify no isolation_level, a plain BEGIN is used, which is equivalent to specifying DEFERRED. Other possible values are IMMEDIATE and EXCLUSIVE.

You can disable the sqlite3 module’s implicit transaction management by setting isolation_level to None. This will leave the underlying sqlite3 library operating in autocommit mode. You can then completely control the transaction state by explicitly issuing BEGIN, ROLLBACK, SAVEPOINT, and RELEASE statements in your code.

Note that executescript() disregards isolation_level; any transaction control must be added explicitly.

Changed in version 3.6: sqlite3 used to implicitly commit an open transaction before DDL statements. This is no longer the case.

Using sqlite3 efficiently

Using shortcut methods

Using the nonstandard execute(), executemany() and executescript() methods of the Connection object, 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.

import sqlite3

langs = [
    ("C++", 1985),
    ("Objective-C", 1984),
]

con = sqlite3.connect(":memory:")

# Create the table
con.execute("create table lang(name, first_appeared)")

# Fill the table
con.executemany("insert into lang(name, first_appeared) values (?, ?)", langs)

# Print the table contents
for row in con.execute("select name, first_appeared from lang"):
    print(row)

print("I just deleted", con.execute("delete from lang").rowcount, "rows")

# close is not a shortcut method and it's not called automatically,
# so the connection object should be closed manually
con.close()

Accessing columns by name instead of by index

One useful feature of the sqlite3 module is the built-in sqlite3.Row class designed to be used as a row factory.

Rows wrapped with this class can be accessed both by index (like tuples) and case-insensitively by name:

import sqlite3

con = sqlite3.connect(":memory:")
con.row_factory = sqlite3.Row

cur = con.cursor()
cur.execute("select 'John' as name, 42 as age")
for row in cur:
    assert row[0] == row["name"]
    assert row["name"] == row["nAmE"]
    assert row[1] == row["age"]
    assert row[1] == row["AgE"]

con.close()

Using the connection as a 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.

import sqlite3

con = sqlite3.connect(":memory:")
con.execute("create table lang (id integer primary key, name varchar unique)")

# Successful, con.commit() is called automatically afterwards
with con:
    con.execute("insert into lang(name) values (?)", ("Python",))

# con.rollback() is called after the with block finishes with an exception, the
# exception is still raised and must be caught
try:
    with con:
        con.execute("insert into lang(name) values (?)", ("Python",))
except sqlite3.IntegrityError:
    print("couldn't add Python twice")

# Connection object used as context manager only commits or rollbacks transactions,
# so the connection object should be closed manually
con.close()

Footnotes

1(1,2)

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.