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整合 SQLite UDF (用户定义函数) 到 webpy 数据库层

整合 SQLite UDF (用户定义函数) 到 webpy 数据库层

问题:

用户在邮件列表中询问,我把它放在这里作为将来使用和参考。

解决:

您可以添加到Python函数到SQLite,并让它们在您的查询调用。

示例:

>>> import sqlite3 as db
>>> conn = db.connect(":memory:")
>>> conn.create_function("sign", 1, lambda val: val and (val > 0 and 1 or -1))
>>> cur = conn.cursor()
>>> cur.execute("select 1, -1")
<sqlite3.Cursor object at 0xb759f2c0>
>>> print cur.fetchall()
[(1, -1)]
>>> cur.execute("select sign(1), sign(-1), sign(0), sign(-99), sign(99)")
<sqlite3.Cursor object at 0xb759f2c0>
>>> print cur.fetchall()
[(1, -1, 0, -1, 1)]
>>> conn.close()
在webpy中,你可以通过游标如db._db_cursor().connection 取得连接对象的引用。 示例:
>>> import web
>>> db = web.database(dbn="sqlite", db=":memory:")
>>> db._db_cursor().connection.create_function("sign", 1, lambda val: val and (val > 0 and 1 or -1))
>>> print db.query("select sign(1), sign(-1), sign(0), sign(-99), sign(99)").list()
[<Storage {'sign(1)': 1, 'sign(-1)': -1, 'sign(99)': 1, 'sign(-99)': -1, 'sign(0)': 0}>]
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