`sqlite3` --- SQLite 数据库 DB-API 2.0 接口模块¶

概述¶

SQLite 是一个C语言库，它可以提供一种轻量级的基于磁盘的数据库，这种数据库不需要独立的服务器进程，也允许需要使用一种非标准的 SQL 查询语言来访问它。一些应用程序可以使用 SQLite 作为内部数据存储。可以用它来创建一个应用程序原型，然后再迁移到更大的数据库，比如 PostgreSQL 或 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.

This document includes four main sections:

Tutorial teaches how to use the sqlite3 module.
Reference describes the classes and functions this module defines.
How-to guides details how to handle specific tasks.
Explanation provides in-depth background on transaction control.

参见

https://www.sqlite.org: SQLite的主页；它的文档详细描述了它所支持的 SQL 方言的语法和可用的数据类型。
https://www.w3schools.com/sql/: 学习 SQL 语法的教程、参考和例子。
PEP 249 - DB-API 2.0 规范: PEP 由 Marc-André Lemburg 撰写。

Tutorial¶

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()

At this point, our database only contains one row:

>>> res = cur.execute('SELECT count(rowid) FROM stocks')
>>> print(res.fetchone())
(1,)

The result is a one-item tuple: one row, with one column. Now, let us insert three more rows of data, using executemany():

>>> data = [
...    ('2006-03-28', 'BUY', 'IBM', 1000, 45.0),
...    ('2006-04-05', 'BUY', 'MSFT', 1000, 72.0),
...    ('2006-04-06', 'SELL', 'IBM', 500, 53.0),
... ]
>>> cur.executemany('INSERT INTO stocks VALUES(?, ?, ?, ?, ?)', data)

Notice that we used ? placeholders to bind data to the query. Always use placeholders instead of string formatting to bind Python values to SQL statements, to avoid SQL injection attacks. See the placeholders how-to for more details.

Then, retrieve the data by iterating over the result of a SELECT statement:

>>> 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)

You've now created an SQLite database using the sqlite3 module.

Reference¶

模块函数和常量¶

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".

注解

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¶: Version number of this module as a string. This is not the version of the SQLite library.

sqlite3.version_info¶: Version number of this module as a tuple of integers. This is not the version of the SQLite library.

sqlite3.sqlite_version¶: Version number of the runtime SQLite library as a string.

sqlite3.sqlite_version_info¶: Version number of the runtime SQLite library as a tuple of integers.

sqlite3.threadsafety¶

Integer constant required by the DB-API, stating the level of thread safety the sqlite3 module supports. Currently hard-coded to 1, meaning "Threads may share the module, but not connections." However, this may not always be true. You can check the underlying SQLite library's compile-time threaded mode using the following query:

import sqlite3
con = sqlite3.connect(":memory:")
con.execute("""
    select * from pragma_compile_options
    where compile_options like 'THREADSAFE=%'
""").fetchall()

Note that the SQLITE_THREADSAFE levels do not match the DB-API 2.0 threadsafety levels.

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=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.

参数

database (path-like object) -- 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.
timeout (float) -- 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.
detect_types (int) -- Control whether and how data types not natively supported by SQLite 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.
isolation_level (str | None) -- The 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 Transaction control for more.
check_same_thread (bool) -- 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.
factory (Connection) -- A custom subclass of Connection to create the connection with, if not the default Connection class.
cached_statements (int) -- The number of statements that sqlite3 should internally cache for this connection, to avoid parsing overhead. By default, 100 statements.
uri (bool) -- If set to True, database is interpreted as a URI 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 Working with SQLite URIs.

返回类型

Connection

引发一个审计事件 sqlite3.connect，附带参数 database。

引发一个审计事件 sqlite3.connect/handle，附带参数 connection_handle。

3.4 新版功能: The uri parameter.

在 3.7 版更改: database 现在可以是一个 path-like object 对象了，不仅仅是字符串。

3.10 新版功能: 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.

它可以用来构建一个 SQLite shell，下面是一个例子：

# 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:
            print("An error occurred:", e.args[0])
        buffer = ""

con.close()

sqlite3.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.

Connection objects¶

class sqlite3.Connection¶

Each open SQLite database is represented by a Connection object, which is created using sqlite3.connect(). Their main purpose is creating Cursor objects, and Transaction control.

参见

Using connection shortcut methods
使用连接作为上下文管理器

An SQLite database connection has the following attributes and methods:

isolation_level¶

This attribute controls the transaction handling 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 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 新版功能.

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.

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)¶

Create or remove a user-defined SQL function.

参数

name (str) -- The name of the SQL function.
narg (int) -- The number of arguments the SQL function can accept. If -1, it may take any number of arguments.
func (callback | None) -- A callable that is called when the SQL function is invoked. The callable must return a type natively supported by SQLite. Set to None to remove an existing SQL function.
deterministic (bool) -- If True, the created SQL function is marked as deterministic, which allows SQLite to perform additional optimizations.

引发

NotSupportedError -- If deterministic is used with SQLite versions older than 3.8.3.

3.8 新版功能: The deterministic parameter.

示例:

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)¶

Create or remove a user-defined SQL aggregate function.

参数

name (str) -- The name of the SQL aggregate function.
n_arg (int) -- The number of arguments the SQL aggregate function can accept. If -1, it may take any number of arguments.
aggregate_class (class | None) --
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.
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.

示例:

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_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.

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 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.

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.

从处理函数返回非零值将终止当前正在执行的查询并导致它引发 OperationalError 异常。

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 of the sqlite3 module and the execution of triggers defined in the current database.

Passing None as trace_callback will disable the trace callback.

注解

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.

3.3 新版功能.

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.

注解

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.

引发一个审计事件 sqlite3.enable_load_extension，附带参数 connection, enabled。

3.2 新版功能.

在 3.10 版更改: 增加了 sqlite3.enable_load_extension 审计事件。

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, /)¶

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

引发一个审计事件 sqlite3.load_extension，附带参数 connection, path。

3.2 新版功能.

在 3.10 版更改: 增加了 sqlite3.load_extension 审计事件。

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.

示例:

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¶

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.

示例:

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

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.

示例:

# 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)¶

Create a backup of an SQLite database.

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

参数

target (Connection) -- The database connection to save the backup to.
pages (int) -- 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.
progress (callback | None) -- 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.
name (str) -- 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.
sleep (float) -- The number of seconds to sleep between successive attempts to back up remaining pages.

示例一，将现有数据库复制到另一个数据库中：

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()

示例二，将现有数据库复制到临时副本中：

import sqlite3

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

3.7 新版功能.

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.

Cursor objects are iterators, meaning that if you execute() a SELECT query, you can simply iterate over the cursor to fetch the resulting rows:
for row in cur.execute("select * from data"):
    print(row)

class sqlite3.Cursor¶

Cursor 游标实例具有以下属性和方法。

execute(sql, parameters=(), /)¶

Execute SQL statement sql. Bind values to the statement using 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 Warning. Use executescript() if you want to execute multiple SQL statements with one call.

If 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 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 execute().

示例:

data = [
    ("row1",),
    ("row2",),
]
# cur is an sqlite3.Cursor object
cur.executemany("insert into t values(?)", data)

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.

示例:

# 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.

请注意 size 形参会涉及到性能方面的考虑。为了获得优化的性能，通常最好是使用 arraysize 属性。如果使用 size 形参，则最好在从一个 fetchmany() 调用到下一个调用之间保持相同的值。

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()¶

立即关闭 cursor（而不是在当 __del__ 被调用的时候）。

从这一时刻起该 cursor 将不再可用，如果再尝试用该 cursor 执行任何操作将引发 ProgrammingError 异常。

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 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.

注解

Inserts into WITHOUT ROWID tables are not recorded.

在 3.6 版更改: 增加了 REPLACE 语句的支持。

arraysize¶: 用于控制 fetchmany() 返回行数的可读取/写入属性。该属性的默认值为 1，表示每次调用将获取单独一行。

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.

对于没有任何匹配行的 SELECT 语句同样会设置该属性。

connection¶

Read-only attribute that provides the SQLite database Connection belonging to the cursor. 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, and supports iteration, repr(), 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. Immediately after a query, it is the first member of each tuple in Cursor.description.

在 3.5 版更改: 添加了对切片操作的支持。

让我们假设我们如上面的例子所示初始化一个表:

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()

现在我们将 Row 插入:

>>> 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

PrepareProtocol objects¶

class sqlite3.PrepareProtocol¶: The PrepareProtocol type's single purpose is to act as a PEP 246 style adaption protocol for objects that can adapt themselves to native SQLite types.

异常¶

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

exception sqlite3.Warning¶: This exception is raised by sqlite3 if an SQL query is not a string, or if multiple statements are passed to execute() or executemany(). 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.

exception sqlite3.InterfaceError¶: This exception is raised by sqlite3 for fetch across rollback, or if sqlite3 is unable to bind parameters. 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¶: 当数据库的关系一致性受到影响时引发的异常。例如外键检查失败等。它是 DatabaseError 的子类。

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 trying to operate on a closed Connection, or trying to execute non-DML statements with executemany(). 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 与 Python 类型¶

SQLite 原生支持如下的类型： NULL，INTEGER，REAL，TEXT，BLOB。

因此可以将以下Python类型发送到SQLite而不会出现任何问题：

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

这是SQLite类型默认转换为Python类型的方式：

SQLite 类型	Python 类型
`NULL`	`None`
`INTEGER`	`int`
`REAL`	`float`
`TEXT`	取决于 `text_factory` , 默认为 `str`
`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, and you can let the sqlite3 module convert SQLite types to Python types via converters.

How-to guides¶

Using 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 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()

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.

让对象自行适配¶

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()

注册可调用的适配器¶

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()

将SQLite 值转换为自定义Python 类型¶

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.

让我们回到 Point 类。我们以字符串形式在 SQLite 中存储了 x 和 y 坐标值。

首先，我们将定义一个转换器函数，它接受这样的字符串作为形参并根据该参数构造一个 Point 对象。

注解

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:

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()

默认适配器和转换器¶

对于 datetime 模块中的 date 和 datetime 类型已提供了默认的适配器。它们将会以 ISO 日期/ISO 时间戳的形式发给 SQLite。

默认转换器使用的注册名称是针对 datetime.date 的 "date" 和针对 datetime.datetime 的 "timestamp"。

通过这种方式，你可以在大多数情况下使用 Python 的 date/timestamp 对象而无须任何额外处理。适配器的格式还与实验性的 SQLite date/time 函数兼容。

下面的示例演示了这一点。

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()

如果存储在 SQLite 中的时间戳的小数位多于 6 个数字，则时间戳转换器会将该值截断至微秒精度。

注解

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)

Using connection shortcut methods¶

Using the execute(), executemany(), and 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.

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()

通过名称而不是索引访问索引¶

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

该类的行装饰器可以用索引（如元组）和不区分大小写的名称访问：

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()

使用连接作为上下文管理器¶

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.

注解

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()

Working with SQLite URIs¶

Some useful URI tricks include:

Open a database in read-only mode:

con = sqlite3.connect("file:template.db?mode=ro", uri=True)

Do not implicitly create a new database file if it does not already exist; will raise OperationalError if unable to create a new 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.execute("create table t(t)")
con1.execute("insert into t values(28)")
con1.commit()
rows = con2.execute("select * from t").fetchall()

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 PEP 249.

If the connection attribute isolation_level is not None, new transactions are implicitly opened before execute() and executemany() executes INSERT, UPDATE, DELETE, or REPLACE statements. Use the commit() and 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 isolation_level attribute.

If 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 in_transaction attribute.

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

在 3.6 版更改: sqlite3 used to implicitly commit an open transaction before DDL statements. This is no longer the case.

`sqlite3` --- SQLite 数据库 DB-API 2.0 接口模块¶

概述¶

Tutorial¶

Reference¶

模块函数和常量¶

Connection objects¶

Cursor objects¶

Row objects¶

PrepareProtocol objects¶

异常¶

SQLite 与 Python 类型¶

How-to guides¶

Using placeholders to bind values in SQL queries¶

Using adapters to store custom Python types in SQLite databases¶

让对象自行适配¶

注册可调用的适配器¶

将SQLite 值转换为自定义Python 类型¶

默认适配器和转换器¶

Adapter and converter recipes¶

Using connection shortcut methods¶

通过名称而不是索引访问索引¶

使用连接作为上下文管理器¶

Working with SQLite URIs¶

Explanation¶

Transaction control¶

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sqlite3 --- SQLite 数据库 DB-API 2.0 接口模块¶

概述¶

Tutorial¶

Reference¶

模块函数和常量¶

Connection objects¶

Cursor objects¶

Row objects¶

PrepareProtocol objects¶

异常¶

SQLite 与 Python 类型¶

How-to guides¶

Using placeholders to bind values in SQL queries¶

Using adapters to store custom Python types in SQLite databases¶

让对象自行适配¶

注册可调用的适配器¶

将SQLite 值转换为自定义Python 类型¶

默认适配器和转换器¶

Adapter and converter recipes¶

Using connection shortcut methods¶

通过名称而不是索引访问索引¶

使用连接作为上下文管理器¶

Working with SQLite URIs¶

Explanation¶

Transaction control¶

`sqlite3` --- SQLite 数据库 DB-API 2.0 接口模块¶