如何从psycopg2游标获取列名列表？

我想要一种直接从所选列名直接生成列标签的通用方法，并且回想起看到python的psycopg2模块支持此功能的情况。

摘自Mark Lutz的“ Programming Python”：

curs.execute("Select * FROM people LIMIT 0")
colnames = [desc[0] for desc in curs.description]

您可以做的另一件事是创建一个游标，您可以使用该游标通过列名来引用您的列（这是导致我首先进入此页面的需要）：

import psycopg2
from psycopg2.extras import RealDictCursor

ps_conn = psycopg2.connect(...)
ps_cursor = psql_conn.cursor(cursor_factory=RealDictCursor)

ps_cursor.execute('select 1 as col_a, 2 as col_b')
my_record = ps_cursor.fetchone()
print (my_record['col_a'],my_record['col_b'])

>> 1, 2

要在单独的查询中获取列名，可以查询information_schema.columns表。

#!/usr/bin/env python3

import psycopg2

if __name__ == '__main__':
  DSN = 'host=YOUR_DATABASE_HOST port=YOUR_DATABASE_PORT dbname=YOUR_DATABASE_NAME user=YOUR_DATABASE_USER'

  column_names = []

  with psycopg2.connect(DSN) as connection:
      with connection.cursor() as cursor:
          cursor.execute("select column_name from information_schema.columns where table_schema = 'YOUR_SCHEMA_NAME' and table_name='YOUR_TABLE_NAME'")
          column_names = [row[0] for row in cursor]

  print("Column names: {}\n".format(column_names))

要在与数据行相同的查询中获取列名，可以使用游标的描述字段：

#!/usr/bin/env python3

import psycopg2

if __name__ == '__main__':
  DSN = 'host=YOUR_DATABASE_HOST port=YOUR_DATABASE_PORT dbname=YOUR_DATABASE_NAME user=YOUR_DATABASE_USER'

  column_names = []
  data_rows = []

  with psycopg2.connect(DSN) as connection:
    with connection.cursor() as cursor:
      cursor.execute("select field1, field2, fieldn from table1")
      column_names = [desc[0] for desc in cursor.description]
      for row in cursor:
        data_rows.append(row)

  print("Column names: {}\n".format(column_names))

如果要从数据库查询中获取命名元组obj，可以使用以下代码段：

from collections import namedtuple

def create_record(obj, fields):
    ''' given obj from db returns named tuple with fields mapped to values '''
    Record = namedtuple("Record", fields)
    mappings = dict(zip(fields, obj))
    return Record(**mappings)

cur.execute("Select * FROM people")
colnames = [desc[0] for desc in cur.description]
rows = cur.fetchall()
cur.close()
result = []
for row in rows:
    result.append(create_record(row, colnames))

这使您可以将记录值当作类属性来访问，即

record.id，record.other_table_column_name等。

甚至更短

from psycopg2.extras import NamedTupleCursor
with cursor(cursor_factory=NamedTupleCursor) as cur:
   cur.execute("Select * ...")
   return cur.fetchall()

执行SQL查询后，编写以下2.7中编写的python脚本

total_fields = len(cursor.description)    
fields_names = [i[0] for i in cursor.description   
    Print fields_names

我注意到，您必须cursor.fetchone()在查询后使用来获取中cursor.description（即[desc[0] for desc in curs.description]）中的列列表

我也曾经遇到过类似的问题。我用一个简单的技巧来解决这个问题。假设列表中有列名，例如

col_name = ['a', 'b', 'c']

然后您可以执行以下操作

for row in cursor.fetchone():
    print zip(col_name, row)

 # You can use this function
 def getColumns(cursorDescription):
     columnList = []
     for tupla in cursorDescription:
         columnList.append(tupla[0])
     return columnList 

#!/usr/bin/python
import psycopg2
#note that we have to import the Psycopg2 extras library!
import psycopg2.extras
import sys

def main():
    conn_string = "host='localhost' dbname='my_database' user='postgres' password='secret'"
    # print the connection string we will use to connect
    print "Connecting to database\n ->%s" % (conn_string)

    # get a connection, if a connect cannot be made an exception will be raised here
    conn = psycopg2.connect(conn_string)

    # conn.cursor will return a cursor object, you can use this query to perform queries
    # note that in this example we pass a cursor_factory argument that will
    # dictionary cursor so COLUMNS will be returned as a dictionary so we
    # can access columns by their name instead of index.
    cursor = conn.cursor(cursor_factory=psycopg2.extras.DictCursor)

    # tell postgres to use more work memory
    work_mem = 2048

    # by passing a tuple as the 2nd argument to the execution function our
    # %s string variable will get replaced with the order of variables in
    # the list. In this case there is only 1 variable.
    # Note that in python you specify a tuple with one item in it by placing
    # a comma after the first variable and surrounding it in parentheses.
    cursor.execute('SET work_mem TO %s', (work_mem,))

    # Then we get the work memory we just set -> we know we only want the
    # first ROW so we call fetchone.
    # then we use bracket access to get the FIRST value.
    # Note that even though we've returned the columns by name we can still
    # access columns by numeric index as well - which is really nice.
    cursor.execute('SHOW work_mem')

    # Call fetchone - which will fetch the first row returned from the
    # database.
    memory = cursor.fetchone()

    # access the column by numeric index:
    # even though we enabled columns by name I'm showing you this to
    # show that you can still access columns by index and iterate over them.
    print "Value: ", memory[0]

    # print the entire row 
    print "Row: ", memory

if __name__ == "__main__":
    main()