在表为空时如何在cx_oracle中获取列信息？

Question

我正在为Python的日志模块开发一个处理器，这个处理器主要是将日志记录到一个Oracle数据库中。

我使用的是cx_Oracle库，但有一点我不知道怎么做，就是当表格为空时，如何获取列的值。

cursor.execute('select * from FOO')
for row in cursor:
    # this is never executed because cursor has no rows
    print '%s\n' % row.description

# This prints none
row = cursor.fetchone()
print str(row)

row = cursor.fetchvars
# prints useful info
for each in row:
    print each

输出结果是：

None
<cx_Oracle.DATETIME with value [None, None, None, None, None, None, None, None, None, None, None, None, None, None, None
, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None
, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None]>
<cx_Oracle.STRING with value [None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None,
None, None, None, None, None, None, None, None, None, None, None, None, None, None, None]>

现在看着变量data，我可以看到数据类型和它们的大小（计算一下空值？），但是缺少了列名。

我该怎么做呢？

Answer 1

我觉得你可能在找的是description这个属性。这个属性会返回一个包含元组的列表，元组里描述了返回数据的列。即使没有返回任何行数据，它也能正常工作，比如：

>>> import cx_Oracle
>>> c = cx_Oracle.connect("username", "password")
>>> cr = c.cursor()
>>> cr.execute("select * from dual where 1=0")
<__builtin__.OracleCursor on <cx_Oracle.Connection to user username@local>>
>>> cr.description
[('DUMMY', <type 'cx_Oracle.STRING'>, 1, 1, 0, 0, 1)]