Python psycopg2使用类对象列表执行_值

我有一个类

Person

，具有

id

、

fname

和

lname

。我的程序将有一个很大的

Person

对象列表，我想将其插入我的

PostgreSQL

数据库

我想通过

psycopg2.execute\u values

方法来实现这一点，该方法要求为我的类定义

\uuuuu getitem\uuuuu

\uuuu getitem\uuuuu

当前正在返回

元组（id，fname，lname）

，这将导致

pscopg2.execute\u values

尝试执行：

插入个人（id，fname，lname）值（（1，'test1'，'test1'）…

import psycopg2.extras


class Person:
    def __init__(self, id, fname, lname):
        self.id = id
        self.fname = fname
        self.lname = lname

    def __len__(self):
        return 1

    def __getitem__(self, item):
        return self.id, self.fname, self.lname


dsn = "user=my_user host=localhost port=5432 dbname=my_db"
query = "insert into persons(id, fname, lname) values %s"

p1 = Person(1, 'test1', 'test1')
p2 = Person(2, 'test2', 'test2')

records = list()
records.append(p1)
records.append(p2)
with psycopg2.connect(dsn=dsn) as conn:
    with conn.cursor() as cursor:
        psycopg2.extras.execute_values(cursor, query, records, template=None, page_size=1000)

psycopg2.ProgrammingError: INSERT has more target columns than expressions
LINE 1: insert into persons(id, fname, lname) values ((1, 'test1', 'test1'))...
                                ^
HINT:  The insertion source is a row expression containing the same number of columns expected by the INSERT. Did you accidentally use extra parentheses?

使用

namedtuple

可以：

from collections import namedtuple
import psycopg2.extras


Person = namedtuple('Person', ['id', 'fname', 'lname'])

dsn = "user=my_user host=localhost port=5432 dbname=my_db"
query = "insert into persons(id, fname, lname) values %s"

p1 = Person(1, 'test1', 'test1')
p2 = Person(2, 'test2', 'test2')

records = list()
records.append(p1)
records.append(p2)

with psycopg2.connect(dsn=dsn) as conn:
    with conn.cursor() as cursor:
        psycopg2.extras.execute_values(cursor, query, records, template=None, page_size=1000)

但是，我想实现一个不同的

\uuuuuueq\uuuu

和

\uuuuuuhash\uuuu

实现。如果有一种方法可以覆盖

namedtuple

的这些方法，那么我愿意使用这种方法

否则，我如何修改

\uu getitem\uuu

以分别返回

id

、

fname

和

lname

，从而使查询变为：

insert into persons(id, fname, lname) values (1, 'test1', 'test1')...

---

定义

\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu

似乎可以达到以下目的：

不确定这是否是推荐的方法，因此我将保持此打开状态，希望有人插话

import psycopg2.extras
from psycopg2.extensions import AsIs, ISQLQuote


class Person:
    def __init__(self, id, fname, lname):
        self.id = id
        self.fname = fname
        self.lname = lname

    def __len__(self):
        return 1

    def __getitem__(self, key):
        return self

    def __conform__(self, protocol):
        if protocol is ISQLQuote:
            return AsIs("{id}, '{fname}', '{lname}'".format(id=self.id, fname=self.fname, lname=self.lname))

        return None


dsn = "user=my_user host=localhost port=5432 dbname=my_db"
query = "insert into persons(id, fname, lname) values %s"

p1 = Person(1, 'test1', 'test1')
p2 = Person(2, 'test2', 'test2')

records = list()
records.append(p1)
records.append(p2)

with psycopg2.connect(dsn=dsn) as conn:
    with conn.cursor() as cursor:
        psycopg2.extras.execute_values(cursor, query, records, template=None, page_size=1000)