Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1 | :mod:`sqlite3` --- DB-API 2.0 interface for SQLite databases |
| 2 | ============================================================ |
| 3 | |
| 4 | .. module:: sqlite3 |
| 5 | :synopsis: A DB-API 2.0 implementation using SQLite 3.x. |
| 6 | .. sectionauthor:: Gerhard Häring <gh@ghaering.de> |
| 7 | |
| 8 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 9 | SQLite is a C library that provides a lightweight disk-based database that |
| 10 | doesn't require a separate server process and allows accessing the database |
| 11 | using a nonstandard variant of the SQL query language. Some applications can use |
| 12 | SQLite for internal data storage. It's also possible to prototype an |
| 13 | application using SQLite and then port the code to a larger database such as |
| 14 | PostgreSQL or Oracle. |
| 15 | |
| 16 | pysqlite was written by Gerhard Häring and provides a SQL interface compliant |
| 17 | with the DB-API 2.0 specification described by :pep:`249`. |
| 18 | |
| 19 | To use the module, you must first create a :class:`Connection` object that |
| 20 | represents the database. Here the data will be stored in the |
| 21 | :file:`/tmp/example` file:: |
| 22 | |
| 23 | conn = sqlite3.connect('/tmp/example') |
| 24 | |
| 25 | You can also supply the special name ``:memory:`` to create a database in RAM. |
| 26 | |
| 27 | Once you have a :class:`Connection`, you can create a :class:`Cursor` object |
| 28 | and call its :meth:`execute` method to perform SQL commands:: |
| 29 | |
| 30 | c = conn.cursor() |
| 31 | |
| 32 | # Create table |
| 33 | c.execute('''create table stocks |
| 34 | (date text, trans text, symbol text, |
| 35 | qty real, price real)''') |
| 36 | |
| 37 | # Insert a row of data |
| 38 | c.execute("""insert into stocks |
| 39 | values ('2006-01-05','BUY','RHAT',100,35.14)""") |
| 40 | |
| 41 | # Save (commit) the changes |
| 42 | conn.commit() |
| 43 | |
| 44 | # We can also close the cursor if we are done with it |
| 45 | c.close() |
| 46 | |
| 47 | Usually your SQL operations will need to use values from Python variables. You |
| 48 | shouldn't assemble your query using Python's string operations because doing so |
| 49 | is insecure; it makes your program vulnerable to an SQL injection attack. |
| 50 | |
| 51 | Instead, use the DB-API's parameter substitution. Put ``?`` as a placeholder |
| 52 | wherever you want to use a value, and then provide a tuple of values as the |
| 53 | second argument to the cursor's :meth:`execute` method. (Other database modules |
| 54 | may use a different placeholder, such as ``%s`` or ``:1``.) For example:: |
| 55 | |
| 56 | # Never do this -- insecure! |
| 57 | symbol = 'IBM' |
| 58 | c.execute("... where symbol = '%s'" % symbol) |
| 59 | |
| 60 | # Do this instead |
| 61 | t = (symbol,) |
| 62 | c.execute('select * from stocks where symbol=?', t) |
| 63 | |
| 64 | # Larger example |
| 65 | for t in (('2006-03-28', 'BUY', 'IBM', 1000, 45.00), |
| 66 | ('2006-04-05', 'BUY', 'MSOFT', 1000, 72.00), |
| 67 | ('2006-04-06', 'SELL', 'IBM', 500, 53.00), |
| 68 | ): |
| 69 | c.execute('insert into stocks values (?,?,?,?,?)', t) |
| 70 | |
Georg Brandl | 9afde1c | 2007-11-01 20:32:30 +0000 | [diff] [blame] | 71 | To retrieve data after executing a SELECT statement, you can either treat the |
| 72 | cursor as an :term:`iterator`, call the cursor's :meth:`fetchone` method to |
| 73 | retrieve a single matching row, or call :meth:`fetchall` to get a list of the |
| 74 | matching rows. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 75 | |
| 76 | This example uses the iterator form:: |
| 77 | |
| 78 | >>> c = conn.cursor() |
| 79 | >>> c.execute('select * from stocks order by price') |
| 80 | >>> for row in c: |
Georg Brandl | 6911e3c | 2007-09-04 07:15:32 +0000 | [diff] [blame] | 81 | ... print(row) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 82 | ... |
| 83 | (u'2006-01-05', u'BUY', u'RHAT', 100, 35.140000000000001) |
| 84 | (u'2006-03-28', u'BUY', u'IBM', 1000, 45.0) |
| 85 | (u'2006-04-06', u'SELL', u'IBM', 500, 53.0) |
| 86 | (u'2006-04-05', u'BUY', u'MSOFT', 1000, 72.0) |
| 87 | >>> |
| 88 | |
| 89 | |
| 90 | .. seealso:: |
| 91 | |
| 92 | http://www.pysqlite.org |
| 93 | The pysqlite web page. |
| 94 | |
| 95 | http://www.sqlite.org |
| 96 | The SQLite web page; the documentation describes the syntax and the available |
| 97 | data types for the supported SQL dialect. |
| 98 | |
| 99 | :pep:`249` - Database API Specification 2.0 |
| 100 | PEP written by Marc-André Lemburg. |
| 101 | |
| 102 | |
| 103 | .. _sqlite3-module-contents: |
| 104 | |
| 105 | Module functions and constants |
| 106 | ------------------------------ |
| 107 | |
| 108 | |
| 109 | .. data:: PARSE_DECLTYPES |
| 110 | |
| 111 | This constant is meant to be used with the *detect_types* parameter of the |
| 112 | :func:`connect` function. |
| 113 | |
| 114 | Setting it makes the :mod:`sqlite3` module parse the declared type for each |
Christian Heimes | 81ee3ef | 2008-05-04 22:42:01 +0000 | [diff] [blame] | 115 | column it returns. It will parse out the first word of the declared type, |
| 116 | i. e. for "integer primary key", it will parse out "integer", or for |
| 117 | "number(10)" it will parse out "number". Then for that column, it will look |
| 118 | into the converters dictionary and use the converter function registered for |
| 119 | that type there. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 120 | |
| 121 | |
| 122 | .. data:: PARSE_COLNAMES |
| 123 | |
| 124 | This constant is meant to be used with the *detect_types* parameter of the |
| 125 | :func:`connect` function. |
| 126 | |
| 127 | Setting this makes the SQLite interface parse the column name for each column it |
| 128 | returns. It will look for a string formed [mytype] in there, and then decide |
| 129 | that 'mytype' is the type of the column. It will try to find an entry of |
| 130 | 'mytype' in the converters dictionary and then use the converter function found |
| 131 | there to return the value. The column name found in :attr:`cursor.description` |
| 132 | is only the first word of the column name, i. e. if you use something like |
| 133 | ``'as "x [datetime]"'`` in your SQL, then we will parse out everything until the |
| 134 | first blank for the column name: the column name would simply be "x". |
| 135 | |
| 136 | |
| 137 | .. function:: connect(database[, timeout, isolation_level, detect_types, factory]) |
| 138 | |
| 139 | Opens a connection to the SQLite database file *database*. You can use |
| 140 | ``":memory:"`` to open a database connection to a database that resides in RAM |
| 141 | instead of on disk. |
| 142 | |
| 143 | When a database is accessed by multiple connections, and one of the processes |
| 144 | modifies the database, the SQLite database is locked until that transaction is |
| 145 | committed. The *timeout* parameter specifies how long the connection should wait |
| 146 | for the lock to go away until raising an exception. The default for the timeout |
| 147 | parameter is 5.0 (five seconds). |
| 148 | |
| 149 | For the *isolation_level* parameter, please see the |
| 150 | :attr:`Connection.isolation_level` property of :class:`Connection` objects. |
| 151 | |
| 152 | SQLite natively supports only the types TEXT, INTEGER, FLOAT, BLOB and NULL. If |
| 153 | you want to use other types you must add support for them yourself. The |
| 154 | *detect_types* parameter and the using custom **converters** registered with the |
| 155 | module-level :func:`register_converter` function allow you to easily do that. |
| 156 | |
| 157 | *detect_types* defaults to 0 (i. e. off, no type detection), you can set it to |
| 158 | any combination of :const:`PARSE_DECLTYPES` and :const:`PARSE_COLNAMES` to turn |
| 159 | type detection on. |
| 160 | |
| 161 | By default, the :mod:`sqlite3` module uses its :class:`Connection` class for the |
| 162 | connect call. You can, however, subclass the :class:`Connection` class and make |
| 163 | :func:`connect` use your class instead by providing your class for the *factory* |
| 164 | parameter. |
| 165 | |
| 166 | Consult the section :ref:`sqlite3-types` of this manual for details. |
| 167 | |
| 168 | The :mod:`sqlite3` module internally uses a statement cache to avoid SQL parsing |
| 169 | overhead. If you want to explicitly set the number of statements that are cached |
| 170 | for the connection, you can set the *cached_statements* parameter. The currently |
| 171 | implemented default is to cache 100 statements. |
| 172 | |
| 173 | |
| 174 | .. function:: register_converter(typename, callable) |
| 175 | |
| 176 | Registers a callable to convert a bytestring from the database into a custom |
| 177 | Python type. The callable will be invoked for all database values that are of |
| 178 | the type *typename*. Confer the parameter *detect_types* of the :func:`connect` |
| 179 | function for how the type detection works. Note that the case of *typename* and |
| 180 | the name of the type in your query must match! |
| 181 | |
| 182 | |
| 183 | .. function:: register_adapter(type, callable) |
| 184 | |
| 185 | Registers a callable to convert the custom Python type *type* into one of |
| 186 | SQLite's supported types. The callable *callable* accepts as single parameter |
Georg Brandl | 5c10664 | 2007-11-29 17:41:05 +0000 | [diff] [blame] | 187 | the Python value, and must return a value of the following types: int, |
Georg Brandl | f694518 | 2008-02-01 11:56:49 +0000 | [diff] [blame] | 188 | float, str, bytes (UTF-8 encoded) or buffer. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 189 | |
| 190 | |
| 191 | .. function:: complete_statement(sql) |
| 192 | |
| 193 | Returns :const:`True` if the string *sql* contains one or more complete SQL |
| 194 | statements terminated by semicolons. It does not verify that the SQL is |
| 195 | syntactically correct, only that there are no unclosed string literals and the |
| 196 | statement is terminated by a semicolon. |
| 197 | |
| 198 | This can be used to build a shell for SQLite, as in the following example: |
| 199 | |
| 200 | |
| 201 | .. literalinclude:: ../includes/sqlite3/complete_statement.py |
| 202 | |
| 203 | |
| 204 | .. function:: enable_callback_tracebacks(flag) |
| 205 | |
| 206 | By default you will not get any tracebacks in user-defined functions, |
| 207 | aggregates, converters, authorizer callbacks etc. If you want to debug them, you |
| 208 | can call this function with *flag* as True. Afterwards, you will get tracebacks |
| 209 | from callbacks on ``sys.stderr``. Use :const:`False` to disable the feature |
| 210 | again. |
| 211 | |
| 212 | |
| 213 | .. _sqlite3-connection-objects: |
| 214 | |
| 215 | Connection Objects |
| 216 | ------------------ |
| 217 | |
| 218 | A :class:`Connection` instance has the following attributes and methods: |
| 219 | |
| 220 | .. attribute:: Connection.isolation_level |
| 221 | |
| 222 | Get or set the current isolation level. None for autocommit mode or one of |
| 223 | "DEFERRED", "IMMEDIATE" or "EXLUSIVE". See section |
| 224 | :ref:`sqlite3-controlling-transactions` for a more detailed explanation. |
| 225 | |
| 226 | |
| 227 | .. method:: Connection.cursor([cursorClass]) |
| 228 | |
| 229 | The cursor method accepts a single optional parameter *cursorClass*. If |
| 230 | supplied, this must be a custom cursor class that extends |
| 231 | :class:`sqlite3.Cursor`. |
| 232 | |
| 233 | |
Gerhard Häring | 0d7d6cf | 2008-03-29 01:32:44 +0000 | [diff] [blame] | 234 | .. method:: Connection.commit() |
| 235 | |
| 236 | This method commits the current transaction. If you don't call this method, |
| 237 | anything you did since the last call to commit() is not visible from from |
| 238 | other database connections. If you wonder why you don't see the data you've |
| 239 | written to the database, please check you didn't forget to call this method. |
| 240 | |
| 241 | .. method:: Connection.rollback() |
| 242 | |
| 243 | This method rolls back any changes to the database since the last call to |
| 244 | :meth:`commit`. |
| 245 | |
| 246 | .. method:: Connection.close() |
| 247 | |
| 248 | This closes the database connection. Note that this does not automatically |
| 249 | call :meth:`commit`. If you just close your database connection without |
| 250 | calling :meth:`commit` first, your changes will be lost! |
| 251 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 252 | .. method:: Connection.execute(sql, [parameters]) |
| 253 | |
| 254 | This is a nonstandard shortcut that creates an intermediate cursor object by |
| 255 | calling the cursor method, then calls the cursor's :meth:`execute` method with |
| 256 | the parameters given. |
| 257 | |
| 258 | |
| 259 | .. method:: Connection.executemany(sql, [parameters]) |
| 260 | |
| 261 | This is a nonstandard shortcut that creates an intermediate cursor object by |
| 262 | calling the cursor method, then calls the cursor's :meth:`executemany` method |
| 263 | with the parameters given. |
| 264 | |
| 265 | |
| 266 | .. method:: Connection.executescript(sql_script) |
| 267 | |
| 268 | This is a nonstandard shortcut that creates an intermediate cursor object by |
| 269 | calling the cursor method, then calls the cursor's :meth:`executescript` method |
| 270 | with the parameters given. |
| 271 | |
| 272 | |
| 273 | .. method:: Connection.create_function(name, num_params, func) |
| 274 | |
| 275 | Creates a user-defined function that you can later use from within SQL |
| 276 | statements under the function name *name*. *num_params* is the number of |
| 277 | parameters the function accepts, and *func* is a Python callable that is called |
| 278 | as the SQL function. |
| 279 | |
Georg Brandl | f694518 | 2008-02-01 11:56:49 +0000 | [diff] [blame] | 280 | The function can return any of the types supported by SQLite: bytes, str, int, |
Georg Brandl | 5c10664 | 2007-11-29 17:41:05 +0000 | [diff] [blame] | 281 | float, buffer and None. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 282 | |
| 283 | Example: |
| 284 | |
| 285 | .. literalinclude:: ../includes/sqlite3/md5func.py |
| 286 | |
| 287 | |
| 288 | .. method:: Connection.create_aggregate(name, num_params, aggregate_class) |
| 289 | |
| 290 | Creates a user-defined aggregate function. |
| 291 | |
| 292 | The aggregate class must implement a ``step`` method, which accepts the number |
| 293 | of parameters *num_params*, and a ``finalize`` method which will return the |
| 294 | final result of the aggregate. |
| 295 | |
| 296 | The ``finalize`` method can return any of the types supported by SQLite: |
Georg Brandl | f694518 | 2008-02-01 11:56:49 +0000 | [diff] [blame] | 297 | bytes, str, int, float, buffer and None. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 298 | |
| 299 | Example: |
| 300 | |
| 301 | .. literalinclude:: ../includes/sqlite3/mysumaggr.py |
| 302 | |
| 303 | |
| 304 | .. method:: Connection.create_collation(name, callable) |
| 305 | |
| 306 | Creates a collation with the specified *name* and *callable*. The callable will |
| 307 | be passed two string arguments. It should return -1 if the first is ordered |
| 308 | lower than the second, 0 if they are ordered equal and 1 if the first is ordered |
| 309 | higher than the second. Note that this controls sorting (ORDER BY in SQL) so |
| 310 | your comparisons don't affect other SQL operations. |
| 311 | |
| 312 | Note that the callable will get its parameters as Python bytestrings, which will |
| 313 | normally be encoded in UTF-8. |
| 314 | |
| 315 | The following example shows a custom collation that sorts "the wrong way": |
| 316 | |
| 317 | .. literalinclude:: ../includes/sqlite3/collation_reverse.py |
| 318 | |
| 319 | To remove a collation, call ``create_collation`` with None as callable:: |
| 320 | |
| 321 | con.create_collation("reverse", None) |
| 322 | |
| 323 | |
| 324 | .. method:: Connection.interrupt() |
| 325 | |
| 326 | You can call this method from a different thread to abort any queries that might |
| 327 | be executing on the connection. The query will then abort and the caller will |
| 328 | get an exception. |
| 329 | |
| 330 | |
| 331 | .. method:: Connection.set_authorizer(authorizer_callback) |
| 332 | |
| 333 | This routine registers a callback. The callback is invoked for each attempt to |
| 334 | access a column of a table in the database. The callback should return |
| 335 | :const:`SQLITE_OK` if access is allowed, :const:`SQLITE_DENY` if the entire SQL |
| 336 | statement should be aborted with an error and :const:`SQLITE_IGNORE` if the |
| 337 | column should be treated as a NULL value. These constants are available in the |
| 338 | :mod:`sqlite3` module. |
| 339 | |
| 340 | The first argument to the callback signifies what kind of operation is to be |
| 341 | authorized. The second and third argument will be arguments or :const:`None` |
| 342 | depending on the first argument. The 4th argument is the name of the database |
| 343 | ("main", "temp", etc.) if applicable. The 5th argument is the name of the |
| 344 | inner-most trigger or view that is responsible for the access attempt or |
| 345 | :const:`None` if this access attempt is directly from input SQL code. |
| 346 | |
| 347 | Please consult the SQLite documentation about the possible values for the first |
| 348 | argument and the meaning of the second and third argument depending on the first |
| 349 | one. All necessary constants are available in the :mod:`sqlite3` module. |
| 350 | |
| 351 | |
Gerhard Häring | 0d7d6cf | 2008-03-29 01:32:44 +0000 | [diff] [blame] | 352 | .. method:: Connection.set_progress_handler(handler, n) |
| 353 | |
Gerhard Häring | 0d7d6cf | 2008-03-29 01:32:44 +0000 | [diff] [blame] | 354 | This routine registers a callback. The callback is invoked for every *n* |
| 355 | instructions of the SQLite virtual machine. This is useful if you want to |
| 356 | get called from SQLite during long-running operations, for example to update |
| 357 | a GUI. |
| 358 | |
| 359 | If you want to clear any previously installed progress handler, call the |
| 360 | method with :const:`None` for *handler*. |
| 361 | |
| 362 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 363 | .. attribute:: Connection.row_factory |
| 364 | |
| 365 | You can change this attribute to a callable that accepts the cursor and the |
| 366 | original row as a tuple and will return the real result row. This way, you can |
| 367 | implement more advanced ways of returning results, such as returning an object |
| 368 | that can also access columns by name. |
| 369 | |
| 370 | Example: |
| 371 | |
| 372 | .. literalinclude:: ../includes/sqlite3/row_factory.py |
| 373 | |
| 374 | If returning a tuple doesn't suffice and you want name-based access to |
| 375 | columns, you should consider setting :attr:`row_factory` to the |
| 376 | highly-optimized :class:`sqlite3.Row` type. :class:`Row` provides both |
| 377 | index-based and case-insensitive name-based access to columns with almost no |
| 378 | memory overhead. It will probably be better than your own custom |
| 379 | dictionary-based approach or even a db_row based solution. |
| 380 | |
Christian Heimes | 5b5e81c | 2007-12-31 16:14:33 +0000 | [diff] [blame] | 381 | .. XXX what's a db_row-based solution? |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 382 | |
| 383 | |
| 384 | .. attribute:: Connection.text_factory |
| 385 | |
| 386 | Using this attribute you can control what objects are returned for the TEXT data |
Georg Brandl | f694518 | 2008-02-01 11:56:49 +0000 | [diff] [blame] | 387 | type. By default, this attribute is set to :class:`str` and the |
| 388 | :mod:`sqlite3` module will return strings for TEXT. If you want to |
| 389 | return bytestrings instead, you can set it to :class:`bytes`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 390 | |
Georg Brandl | f694518 | 2008-02-01 11:56:49 +0000 | [diff] [blame] | 391 | For efficiency reasons, there's also a way to return :class:`str` objects |
| 392 | only for non-ASCII data, and :class:`bytes` otherwise. To activate it, set |
| 393 | this attribute to :const:`sqlite3.OptimizedUnicode`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 394 | |
| 395 | You can also set it to any other callable that accepts a single bytestring |
| 396 | parameter and returns the resulting object. |
| 397 | |
| 398 | See the following example code for illustration: |
| 399 | |
| 400 | .. literalinclude:: ../includes/sqlite3/text_factory.py |
| 401 | |
| 402 | |
| 403 | .. attribute:: Connection.total_changes |
| 404 | |
| 405 | Returns the total number of database rows that have been modified, inserted, or |
| 406 | deleted since the database connection was opened. |
| 407 | |
| 408 | |
Christian Heimes | bbe741d | 2008-03-28 10:53:29 +0000 | [diff] [blame] | 409 | .. attribute:: Connection.iterdump |
| 410 | |
| 411 | Returns an iterator to dump the database in an SQL text format. Useful when |
| 412 | saving an in-memory database for later restoration. This function provides |
| 413 | the same capabilities as the :kbd:`.dump` command in the :program:`sqlite3` |
| 414 | shell. |
| 415 | |
Christian Heimes | bbe741d | 2008-03-28 10:53:29 +0000 | [diff] [blame] | 416 | Example:: |
| 417 | |
| 418 | # Convert file existing_db.db to SQL dump file dump.sql |
| 419 | import sqlite3, os |
| 420 | |
| 421 | con = sqlite3.connect('existing_db.db') |
| 422 | full_dump = os.linesep.join([line for line in con.iterdump()]) |
| 423 | f = open('dump.sql', 'w') |
| 424 | f.writelines(full_dump) |
| 425 | f.close() |
| 426 | |
| 427 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 428 | .. _sqlite3-cursor-objects: |
| 429 | |
| 430 | Cursor Objects |
| 431 | -------------- |
| 432 | |
| 433 | A :class:`Cursor` instance has the following attributes and methods: |
| 434 | |
| 435 | |
| 436 | .. method:: Cursor.execute(sql, [parameters]) |
| 437 | |
Christian Heimes | fdab48e | 2008-01-20 09:06:41 +0000 | [diff] [blame] | 438 | Executes an SQL statement. The SQL statement may be parametrized (i. e. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 439 | placeholders instead of SQL literals). The :mod:`sqlite3` module supports two |
| 440 | kinds of placeholders: question marks (qmark style) and named placeholders |
| 441 | (named style). |
| 442 | |
| 443 | This example shows how to use parameters with qmark style: |
| 444 | |
| 445 | .. literalinclude:: ../includes/sqlite3/execute_1.py |
| 446 | |
| 447 | This example shows how to use the named style: |
| 448 | |
| 449 | .. literalinclude:: ../includes/sqlite3/execute_2.py |
| 450 | |
| 451 | :meth:`execute` will only execute a single SQL statement. If you try to execute |
| 452 | more than one statement with it, it will raise a Warning. Use |
| 453 | :meth:`executescript` if you want to execute multiple SQL statements with one |
| 454 | call. |
| 455 | |
| 456 | |
| 457 | .. method:: Cursor.executemany(sql, seq_of_parameters) |
| 458 | |
Christian Heimes | fdab48e | 2008-01-20 09:06:41 +0000 | [diff] [blame] | 459 | Executes an SQL command against all parameter sequences or mappings found in |
Georg Brandl | 9afde1c | 2007-11-01 20:32:30 +0000 | [diff] [blame] | 460 | the sequence *sql*. The :mod:`sqlite3` module also allows using an |
| 461 | :term:`iterator` yielding parameters instead of a sequence. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 462 | |
| 463 | .. literalinclude:: ../includes/sqlite3/executemany_1.py |
| 464 | |
Georg Brandl | 9afde1c | 2007-11-01 20:32:30 +0000 | [diff] [blame] | 465 | Here's a shorter example using a :term:`generator`: |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 466 | |
| 467 | .. literalinclude:: ../includes/sqlite3/executemany_2.py |
| 468 | |
| 469 | |
| 470 | .. method:: Cursor.executescript(sql_script) |
| 471 | |
| 472 | This is a nonstandard convenience method for executing multiple SQL statements |
| 473 | at once. It issues a COMMIT statement first, then executes the SQL script it |
| 474 | gets as a parameter. |
| 475 | |
Georg Brandl | f694518 | 2008-02-01 11:56:49 +0000 | [diff] [blame] | 476 | *sql_script* can be an instance of :class:`str` or :class:`bytes`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 477 | |
| 478 | Example: |
| 479 | |
| 480 | .. literalinclude:: ../includes/sqlite3/executescript.py |
| 481 | |
| 482 | |
Gerhard Häring | 0d7d6cf | 2008-03-29 01:32:44 +0000 | [diff] [blame] | 483 | .. method:: Cursor.fetchone() |
| 484 | |
Christian Heimes | fdab48e | 2008-01-20 09:06:41 +0000 | [diff] [blame] | 485 | Fetches the next row of a query result set, returning a single sequence, |
| 486 | or ``None`` when no more data is available. |
| 487 | |
| 488 | |
| 489 | .. method:: Cursor.fetchmany([size=cursor.arraysize]) |
Gerhard Häring | 0d7d6cf | 2008-03-29 01:32:44 +0000 | [diff] [blame] | 490 | |
Christian Heimes | fdab48e | 2008-01-20 09:06:41 +0000 | [diff] [blame] | 491 | Fetches the next set of rows of a query result, returning a list. An empty |
| 492 | list is returned when no more rows are available. |
Gerhard Häring | 0d7d6cf | 2008-03-29 01:32:44 +0000 | [diff] [blame] | 493 | |
Christian Heimes | fdab48e | 2008-01-20 09:06:41 +0000 | [diff] [blame] | 494 | The number of rows to fetch per call is specified by the *size* parameter. |
| 495 | If it is not given, the cursor's arraysize determines the number of rows |
| 496 | to be fetched. The method should try to fetch as many rows as indicated by |
| 497 | the size parameter. If this is not possible due to the specified number of |
| 498 | rows not being available, fewer rows may be returned. |
Gerhard Häring | 0d7d6cf | 2008-03-29 01:32:44 +0000 | [diff] [blame] | 499 | |
Christian Heimes | fdab48e | 2008-01-20 09:06:41 +0000 | [diff] [blame] | 500 | Note there are performance considerations involved with the *size* parameter. |
| 501 | For optimal performance, it is usually best to use the arraysize attribute. |
| 502 | If the *size* parameter is used, then it is best for it to retain the same |
| 503 | value from one :meth:`fetchmany` call to the next. |
Gerhard Häring | 0d7d6cf | 2008-03-29 01:32:44 +0000 | [diff] [blame] | 504 | |
| 505 | .. method:: Cursor.fetchall() |
Christian Heimes | fdab48e | 2008-01-20 09:06:41 +0000 | [diff] [blame] | 506 | |
| 507 | Fetches all (remaining) rows of a query result, returning a list. Note that |
| 508 | the cursor's arraysize attribute can affect the performance of this operation. |
| 509 | An empty list is returned when no rows are available. |
| 510 | |
| 511 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 512 | .. attribute:: Cursor.rowcount |
| 513 | |
| 514 | Although the :class:`Cursor` class of the :mod:`sqlite3` module implements this |
| 515 | attribute, the database engine's own support for the determination of "rows |
| 516 | affected"/"rows selected" is quirky. |
| 517 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 518 | For ``DELETE`` statements, SQLite reports :attr:`rowcount` as 0 if you make a |
| 519 | ``DELETE FROM table`` without any condition. |
| 520 | |
| 521 | For :meth:`executemany` statements, the number of modifications are summed up |
| 522 | into :attr:`rowcount`. |
| 523 | |
| 524 | As required by the Python DB API Spec, the :attr:`rowcount` attribute "is -1 in |
| 525 | case no executeXX() has been performed on the cursor or the rowcount of the last |
| 526 | operation is not determinable by the interface". |
| 527 | |
Guido van Rossum | 04110fb | 2007-08-24 16:32:05 +0000 | [diff] [blame] | 528 | This includes ``SELECT`` statements because we cannot determine the number of |
| 529 | rows a query produced until all rows were fetched. |
| 530 | |
Gerhard Häring | d337279 | 2008-03-29 19:13:55 +0000 | [diff] [blame] | 531 | .. attribute:: Cursor.lastrowid |
| 532 | |
| 533 | This read-only attribute provides the rowid of the last modified row. It is |
| 534 | only set if you issued a ``INSERT`` statement using the :meth:`execute` |
| 535 | method. For operations other than ``INSERT`` or when :meth:`executemany` is |
| 536 | called, :attr:`lastrowid` is set to :const:`None`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 537 | |
| 538 | .. _sqlite3-types: |
| 539 | |
| 540 | SQLite and Python types |
| 541 | ----------------------- |
| 542 | |
| 543 | |
| 544 | Introduction |
| 545 | ^^^^^^^^^^^^ |
| 546 | |
| 547 | SQLite natively supports the following types: NULL, INTEGER, REAL, TEXT, BLOB. |
| 548 | |
| 549 | The following Python types can thus be sent to SQLite without any problem: |
| 550 | |
Georg Brandl | f694518 | 2008-02-01 11:56:49 +0000 | [diff] [blame] | 551 | +-------------------------------+-------------+ |
| 552 | | Python type | SQLite type | |
| 553 | +===============================+=============+ |
| 554 | | ``None`` | NULL | |
| 555 | +-------------------------------+-------------+ |
| 556 | | :class:`int` | INTEGER | |
| 557 | +-------------------------------+-------------+ |
| 558 | | :class:`float` | REAL | |
| 559 | +-------------------------------+-------------+ |
| 560 | | :class:`bytes` (UTF8-encoded) | TEXT | |
| 561 | +-------------------------------+-------------+ |
| 562 | | :class:`str` | TEXT | |
| 563 | +-------------------------------+-------------+ |
| 564 | | :class:`buffer` | BLOB | |
| 565 | +-------------------------------+-------------+ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 566 | |
| 567 | This is how SQLite types are converted to Python types by default: |
| 568 | |
| 569 | +-------------+---------------------------------------------+ |
| 570 | | SQLite type | Python type | |
| 571 | +=============+=============================================+ |
| 572 | | ``NULL`` | None | |
| 573 | +-------------+---------------------------------------------+ |
Georg Brandl | 5c10664 | 2007-11-29 17:41:05 +0000 | [diff] [blame] | 574 | | ``INTEGER`` | int | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 575 | +-------------+---------------------------------------------+ |
| 576 | | ``REAL`` | float | |
| 577 | +-------------+---------------------------------------------+ |
Georg Brandl | f694518 | 2008-02-01 11:56:49 +0000 | [diff] [blame] | 578 | | ``TEXT`` | depends on text_factory, str by default | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 579 | +-------------+---------------------------------------------+ |
| 580 | | ``BLOB`` | buffer | |
| 581 | +-------------+---------------------------------------------+ |
| 582 | |
| 583 | The type system of the :mod:`sqlite3` module is extensible in two ways: you can |
| 584 | store additional Python types in a SQLite database via object adaptation, and |
| 585 | you can let the :mod:`sqlite3` module convert SQLite types to different Python |
| 586 | types via converters. |
| 587 | |
| 588 | |
| 589 | Using adapters to store additional Python types in SQLite databases |
| 590 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 591 | |
| 592 | As described before, SQLite supports only a limited set of types natively. To |
| 593 | use other Python types with SQLite, you must **adapt** them to one of the |
Georg Brandl | 5c10664 | 2007-11-29 17:41:05 +0000 | [diff] [blame] | 594 | sqlite3 module's supported types for SQLite: one of NoneType, int, float, |
Georg Brandl | f694518 | 2008-02-01 11:56:49 +0000 | [diff] [blame] | 595 | str, bytes, buffer. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 596 | |
| 597 | The :mod:`sqlite3` module uses Python object adaptation, as described in |
| 598 | :pep:`246` for this. The protocol to use is :class:`PrepareProtocol`. |
| 599 | |
| 600 | There are two ways to enable the :mod:`sqlite3` module to adapt a custom Python |
| 601 | type to one of the supported ones. |
| 602 | |
| 603 | |
| 604 | Letting your object adapt itself |
| 605 | """""""""""""""""""""""""""""""" |
| 606 | |
| 607 | This is a good approach if you write the class yourself. Let's suppose you have |
| 608 | a class like this:: |
| 609 | |
| 610 | class Point(object): |
| 611 | def __init__(self, x, y): |
| 612 | self.x, self.y = x, y |
| 613 | |
| 614 | Now you want to store the point in a single SQLite column. First you'll have to |
| 615 | choose one of the supported types first to be used for representing the point. |
| 616 | Let's just use str and separate the coordinates using a semicolon. Then you need |
| 617 | to give your class a method ``__conform__(self, protocol)`` which must return |
| 618 | the converted value. The parameter *protocol* will be :class:`PrepareProtocol`. |
| 619 | |
| 620 | .. literalinclude:: ../includes/sqlite3/adapter_point_1.py |
| 621 | |
| 622 | |
| 623 | Registering an adapter callable |
| 624 | """"""""""""""""""""""""""""""" |
| 625 | |
| 626 | The other possibility is to create a function that converts the type to the |
| 627 | string representation and register the function with :meth:`register_adapter`. |
| 628 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 629 | .. literalinclude:: ../includes/sqlite3/adapter_point_2.py |
| 630 | |
| 631 | The :mod:`sqlite3` module has two default adapters for Python's built-in |
| 632 | :class:`datetime.date` and :class:`datetime.datetime` types. Now let's suppose |
| 633 | we want to store :class:`datetime.datetime` objects not in ISO representation, |
| 634 | but as a Unix timestamp. |
| 635 | |
| 636 | .. literalinclude:: ../includes/sqlite3/adapter_datetime.py |
| 637 | |
| 638 | |
| 639 | Converting SQLite values to custom Python types |
| 640 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 641 | |
| 642 | Writing an adapter lets you send custom Python types to SQLite. But to make it |
| 643 | really useful we need to make the Python to SQLite to Python roundtrip work. |
| 644 | |
| 645 | Enter converters. |
| 646 | |
| 647 | Let's go back to the :class:`Point` class. We stored the x and y coordinates |
| 648 | separated via semicolons as strings in SQLite. |
| 649 | |
| 650 | First, we'll define a converter function that accepts the string as a parameter |
| 651 | and constructs a :class:`Point` object from it. |
| 652 | |
| 653 | .. note:: |
| 654 | |
| 655 | Converter functions **always** get called with a string, no matter under which |
| 656 | data type you sent the value to SQLite. |
| 657 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 658 | :: |
| 659 | |
| 660 | def convert_point(s): |
| 661 | x, y = map(float, s.split(";")) |
| 662 | return Point(x, y) |
| 663 | |
| 664 | Now you need to make the :mod:`sqlite3` module know that what you select from |
| 665 | the database is actually a point. There are two ways of doing this: |
| 666 | |
| 667 | * Implicitly via the declared type |
| 668 | |
| 669 | * Explicitly via the column name |
| 670 | |
| 671 | Both ways are described in section :ref:`sqlite3-module-contents`, in the entries |
| 672 | for the constants :const:`PARSE_DECLTYPES` and :const:`PARSE_COLNAMES`. |
| 673 | |
| 674 | The following example illustrates both approaches. |
| 675 | |
| 676 | .. literalinclude:: ../includes/sqlite3/converter_point.py |
| 677 | |
| 678 | |
| 679 | Default adapters and converters |
| 680 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 681 | |
| 682 | There are default adapters for the date and datetime types in the datetime |
| 683 | module. They will be sent as ISO dates/ISO timestamps to SQLite. |
| 684 | |
| 685 | The default converters are registered under the name "date" for |
| 686 | :class:`datetime.date` and under the name "timestamp" for |
| 687 | :class:`datetime.datetime`. |
| 688 | |
| 689 | This way, you can use date/timestamps from Python without any additional |
| 690 | fiddling in most cases. The format of the adapters is also compatible with the |
| 691 | experimental SQLite date/time functions. |
| 692 | |
| 693 | The following example demonstrates this. |
| 694 | |
| 695 | .. literalinclude:: ../includes/sqlite3/pysqlite_datetime.py |
| 696 | |
| 697 | |
| 698 | .. _sqlite3-controlling-transactions: |
| 699 | |
| 700 | Controlling Transactions |
| 701 | ------------------------ |
| 702 | |
| 703 | By default, the :mod:`sqlite3` module opens transactions implicitly before a |
| 704 | Data Modification Language (DML) statement (i.e. INSERT/UPDATE/DELETE/REPLACE), |
| 705 | and commits transactions implicitly before a non-DML, non-query statement (i. e. |
| 706 | anything other than SELECT/INSERT/UPDATE/DELETE/REPLACE). |
| 707 | |
| 708 | So if you are within a transaction and issue a command like ``CREATE TABLE |
| 709 | ...``, ``VACUUM``, ``PRAGMA``, the :mod:`sqlite3` module will commit implicitly |
| 710 | before executing that command. There are two reasons for doing that. The first |
| 711 | is that some of these commands don't work within transactions. The other reason |
| 712 | is that pysqlite needs to keep track of the transaction state (if a transaction |
| 713 | is active or not). |
| 714 | |
| 715 | You can control which kind of "BEGIN" statements pysqlite implicitly executes |
| 716 | (or none at all) via the *isolation_level* parameter to the :func:`connect` |
| 717 | call, or via the :attr:`isolation_level` property of connections. |
| 718 | |
| 719 | If you want **autocommit mode**, then set :attr:`isolation_level` to None. |
| 720 | |
| 721 | Otherwise leave it at its default, which will result in a plain "BEGIN" |
| 722 | statement, or set it to one of SQLite's supported isolation levels: DEFERRED, |
| 723 | IMMEDIATE or EXCLUSIVE. |
| 724 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 725 | |
| 726 | |
| 727 | Using pysqlite efficiently |
| 728 | -------------------------- |
| 729 | |
| 730 | |
| 731 | Using shortcut methods |
| 732 | ^^^^^^^^^^^^^^^^^^^^^^ |
| 733 | |
| 734 | Using the nonstandard :meth:`execute`, :meth:`executemany` and |
| 735 | :meth:`executescript` methods of the :class:`Connection` object, your code can |
| 736 | be written more concisely because you don't have to create the (often |
| 737 | superfluous) :class:`Cursor` objects explicitly. Instead, the :class:`Cursor` |
| 738 | objects are created implicitly and these shortcut methods return the cursor |
| 739 | objects. This way, you can execute a SELECT statement and iterate over it |
| 740 | directly using only a single call on the :class:`Connection` object. |
| 741 | |
| 742 | .. literalinclude:: ../includes/sqlite3/shortcut_methods.py |
| 743 | |
| 744 | |
| 745 | Accessing columns by name instead of by index |
| 746 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 747 | |
| 748 | One useful feature of the :mod:`sqlite3` module is the builtin |
| 749 | :class:`sqlite3.Row` class designed to be used as a row factory. |
| 750 | |
| 751 | Rows wrapped with this class can be accessed both by index (like tuples) and |
| 752 | case-insensitively by name: |
| 753 | |
| 754 | .. literalinclude:: ../includes/sqlite3/rowclass.py |
| 755 | |
Gerhard Häring | 0d7d6cf | 2008-03-29 01:32:44 +0000 | [diff] [blame] | 756 | |
| 757 | Using the connection as a context manager |
| 758 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| 759 | |
Gerhard Häring | 0d7d6cf | 2008-03-29 01:32:44 +0000 | [diff] [blame] | 760 | Connection objects can be used as context managers |
| 761 | that automatically commit or rollback transactions. In the event of an |
| 762 | exception, the transaction is rolled back; otherwise, the transaction is |
| 763 | committed: |
| 764 | |
| 765 | .. literalinclude:: ../includes/sqlite3/ctx_manager.py |