gh-95432: Add doctest for sqlite3 tutorial (GH-96193)

(cherry picked from commit 04c73e5)

Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>

Doc/library/sqlite3.rst

@@ -8,6 +8,15 @@
 
 **Source code:** :source:`Lib/sqlite3/`
 
+.. Make sure we always doctest the tutorial with an empty database.
+
+.. testsetup::
+
+   import sqlite3
+   src = sqlite3.connect(":memory:", isolation_level=None)
+   dst = sqlite3.connect("tutorial.db", isolation_level=None)
+   src.backup(dst)
+   del src, dst
 
 .. _sqlite3-intro:
 
@@ -65,7 +74,9 @@ First, we need to create a new database and open
 a database connection to allow :mod:`!sqlite3` to work with it.
 Call :func:`sqlite3.connect` to to create a connection to
 the database :file:`tutorial.db` in the current working directory,
-implicitly creating it if it does not exist::
+implicitly creating it if it does not exist:
+
+.. testcode::
 
    import sqlite3
    con = sqlite3.connect("tutorial.db")
@@ -75,7 +86,9 @@ represents the connection to the on-disk database.
 
 In order to execute SQL statements and fetch results from SQL queries,
 we will need to use a database cursor.
-Call :meth:`con.cursor() <Connection.cursor>` to create the :class:`Cursor`::
+Call :meth:`con.cursor() <Connection.cursor>` to create the :class:`Cursor`:
+
+.. testcode::
 
    cur = con.cursor()
 
@@ -86,7 +99,9 @@ For simplicity, we can just use column names in the table declaration --
 thanks to the `flexible typing`_ feature of SQLite,
 specifying the data types is optional.
 Execute the ``CREATE TABLE`` statement
-by calling :meth:`cur.execute(...) <Cursor.execute>`::
+by calling :meth:`cur.execute(...) <Cursor.execute>`:
+
+.. testcode::
 
    cur.execute("CREATE TABLE movie(title, year, score)")
 
@@ -99,7 +114,9 @@ which should now contain an entry for the ``movie`` table definition
 (see `The Schema Table`_ for details).
 Execute that query by calling :meth:`cur.execute(...) <Cursor.execute>`,
 assign the result to ``res``,
-and call :meth:`res.fetchone() <Cursor.fetchone>` to fetch the resulting row::
+and call :meth:`res.fetchone() <Cursor.fetchone>` to fetch the resulting row:
+
+.. doctest::
 
    >>> res = cur.execute("SELECT name FROM sqlite_master")
    >>> res.fetchone()
@@ -108,15 +125,19 @@ and call :meth:`res.fetchone() <Cursor.fetchone>` to fetch the resulting row::
 We can see that the table has been created,
 as the query returns a :class:`tuple` containing the table's name.
 If we query ``sqlite_master`` for a non-existent table ``spam``,
-:meth:`!res.fetchone()` will return ``None``::
+:meth:`!res.fetchone()` will return ``None``:
+
+.. doctest::
 
    >>> res = cur.execute("SELECT name FROM sqlite_master WHERE name='spam'")
    >>> res.fetchone() is None
    True
 
 Now, add two rows of data supplied as SQL literals
 by executing an ``INSERT`` statement,
-once again by calling :meth:`cur.execute(...) <Cursor.execute>`::
+once again by calling :meth:`cur.execute(...) <Cursor.execute>`:
+
+.. testcode::
 
    cur.execute("""
        INSERT INTO movie VALUES
@@ -128,15 +149,19 @@ The ``INSERT`` statement implicitly opens a transaction,
 which needs to be committed before changes are saved in the database
 (see :ref:`sqlite3-controlling-transactions` for details).
 Call :meth:`con.commit() <Connection.commit>` on the connection object
-to commit the transaction::
+to commit the transaction:
+
+.. testcode::
 
    con.commit()
 
 We can verify that the data was inserted correctly
 by executing a ``SELECT`` query.
 Use the now-familiar :meth:`cur.execute(...) <Cursor.execute>` to
 assign the result to ``res``,
-and call :meth:`res.fetchall() <Cursor.fetchall>` to return all resulting rows::
+and call :meth:`res.fetchall() <Cursor.fetchall>` to return all resulting rows:
+
+.. doctest::
 
    >>> res = cur.execute("SELECT score FROM movie")
    >>> res.fetchall()
@@ -146,7 +171,9 @@ The result is a :class:`list` of two :class:`!tuple`\s, one per row,
 each containing that row's ``score`` value.
 
 Now, insert three more rows by calling
-:meth:`cur.executemany(...) <Cursor.executemany>`::
+:meth:`cur.executemany(...) <Cursor.executemany>`:
+
+.. testcode::
 
    data = [
        ("Monty Python Live at the Hollywood Bowl", 1982, 7.9),
@@ -164,14 +191,16 @@ to avoid `SQL injection attacks`_
 
 We can verify that the new rows were inserted
 by executing a ``SELECT`` query,
-this time iterating over the results of the query::
+this time iterating over the results of the query:
+
+.. doctest::
 
    >>> for row in cur.execute("SELECT year, title FROM movie ORDER BY year"):
    ...     print(row)
-   (1971, "And Now for Something Completely Different")
-   (1975, "Monty Python and the Holy Grail")
+   (1971, 'And Now for Something Completely Different')
+   (1975, 'Monty Python and the Holy Grail')
    (1979, "Monty Python's Life of Brian")
-   (1982, "Monty Python Live at the Hollywood Bowl")
+   (1982, 'Monty Python Live at the Hollywood Bowl')
    (1983, "Monty Python's The Meaning of Life")
 
 Each row is a two-item :class:`tuple` of ``(year, title)``,
@@ -180,15 +209,17 @@ matching the columns selected in the query.
 Finally, verify that the database has been written to disk
 by calling :meth:`con.close() <Connection.close>`
 to close the existing connection, opening a new one,
-creating a new cursor, then querying the database::
+creating a new cursor, then querying the database:
+
+.. doctest::
 
    >>> con.close()
    >>> new_con = sqlite3.connect("tutorial.db")
    >>> new_cur = new_con.cursor()
-   >>> res = new_cur.execute("SELECT year, title FROM movie ORDER BY score DESC"):
+   >>> res = new_cur.execute("SELECT title, year FROM movie ORDER BY score DESC")
    >>> title, year = res.fetchone()
    >>> print(f'The highest scoring Monty Python movie is {title!r}, released in {year}')
-   'The highest scoring Monty Python movie is "Monty Python and the Holy Grail", released in 1975'
+   The highest scoring Monty Python movie is 'Monty Python and the Holy Grail', released in 1975
 
 You've now created an SQLite database using the :mod:`!sqlite3` module,
 inserted data and retrieved values from it in multiple ways.