psycopg2：在连接到 PostgreSQL 的 Python 中显示多列数据时出错

发布于 2024-12-10 12:38:08 字数 513 浏览 0 评论 0原文

我正在使用 psycopg2 连接到 Postgres 数据库并使用 Python 在屏幕上返回查询结果。我只能返回一列数据，不能像 PSQL 那样返回很多列。请看我的代码。我哪里做错了？

我们将非常感谢您的友好回复。

#!/usr/bin/python


import psycopg2

CONNSTR = """
  host=localhost 
  dbname=wa
  user=super
  password=test
  port=5432"""
cxn = psycopg2.connect(CONNSTR)
cur = cxn.cursor()
cur.execute("""SELECT procpid,usename,current_query FROM pg_stat_activity;""")

rows = cur.fetchall()

print "\nShow me the query results:\n"
for row in rows:
        print "   ", row[1]

原文

I am using psycopg2 to connect to Postgres database and return query results on the screen using Python. I can only return one column of data, not many columns like PSQL does. Please see my code. Where did I do wrong?

Your kind response would be greatly appreciated.

#!/usr/bin/python


import psycopg2

CONNSTR = """
  host=localhost 
  dbname=wa
  user=super
  password=test
  port=5432"""
cxn = psycopg2.connect(CONNSTR)
cur = cxn.cursor()
cur.execute("""SELECT procpid,usename,current_query FROM pg_stat_activity;""")

rows = cur.fetchall()

print "\nShow me the query results:\n"
for row in rows:
        print "   ", row[1]

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素衣风尘叹 2024-12-17 12:38:08

我在 initd.org/psycopg/docs/cursor.html 上找到了答案。这是正确的代码。请查看最后两行代码的更改。

为了澄清起见，第一个版本的代码仅返回一列数据。下面列出的第二个版本将返回，实际上它将显示/打印我选择的所有列。

#!/usr/bin/python

import psycopg2

CONNSTR = """
  host=localhost 
  dbname=wa
  user=super
  password=test
  port=5432"""
cxn = psycopg2.connect(CONNSTR)
cur = cxn.cursor()
cur.execute("""SELECT procpid,usename,current_query FROM pg_stat_activity;""")

for rows in cur: 
print rows

I found the answer on initd.org/psycopg/docs/cursor.html. Here is the correct code. Please see the last two lines of code with the changes.

For clarification, the first version of code only returns one column of data. The 2nd version listed below will return, actually it will display/print, all the columns I selected.

#!/usr/bin/python

import psycopg2

CONNSTR = """
  host=localhost 
  dbname=wa
  user=super
  password=test
  port=5432"""
cxn = psycopg2.connect(CONNSTR)
cur = cxn.cursor()
cur.execute("""SELECT procpid,usename,current_query FROM pg_stat_activity;""")

for rows in cur: 
print rows

回复收藏 0 原文

我最亲爱的 2024-12-17 12:38:08

我不太清楚你想要实现什么目标。

如果您只需要一列数据，那么您可以在 SQL 查询中过滤掉该数据。例如：

cur.execute("""SELECT procpid FROM pg_stat_activity;""")

psycopg2 仍然会返回一个元组数组，其中每个元组都包含您请求的列。如果您不需要元组和列数据的值数组，那么您可以使用以下方法转换它们：

colum_data = [r[1] for r in rows]

如果这不是您所要求的，请重新表述您的问题。

It is not quite clear to me what you are trying to achieve.

If you only need one column of data, then you can filter that out in the SQL query. For instance:

cur.execute("""SELECT procpid FROM pg_stat_activity;""")

Still psycopg2 will return an array of tuples, where each tuple contains the columns you requested for. If you do not want the tuples and just an array of values for your the column-data, then you can convert them using: