数据库游标

Question

In Python, what is a database "cursor" most like?

1. A method within a class

2. A Python dictionary

3. A function

4. A file handle

I have searched on internet but I am not getting proper justification of this question.

Answer 1

According to the PEP 249 (Python Database API Specification) , it is an object which is expected to have certain attributes and methods defined. Optionally, cursors can support an iteration protocol .

This is though a spec, and, your database driver of choice may not follow the API specification. But, this is a more or less general answer to the rather general question.

Answer 2

Probably it is most like a file handle.

That does not mean that it is a file handle, and a cursor is actually an object - an instance of a Cursor class (depending on the actual db driver in use).

The reason that it's similar to a file handle is that you can consume data from it, but (in general) you can't go back to previously consumed data. Consumption of data is therefore unidirectional. Reading from a file handle returns characters/bytes, reading from a cursor returns rows.