Question

我写了一个Python函数来获取一个列表（可变长度）并将其插入一个表（与每个列表中的值具有相同的列数）：

ps.cur = psycopg_cursor

def load_lists(list_of_lists, table):
    # Get number of columns in table
    sql = """
          SELECT column_name FROM information_schema.columns
          WHERE table_schema = 'public'
          AND table_name = '{}'
          """.format(table)
    ps.cur.execute(sql)
    columns_list = [i[0] for i in ps.cur.fetchall()]
    # Insert list of lists into table
    columns = '(' + ','.join(columns_list) + ')'
    parameters = '(' + ','.join(['%%s' for i in columns_list]) + ')'
    for i in list_of_lists:
        sql = """
              INSERT INTO {} {}
              VALUES {}
              """.format(table, columns, parameters)
        values = tuple([j for j in i])
        ps.cur.execute(sql, values)

我得到以下回溯尝试执行函数：

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "psyco.py", line 24, in load_lists
    ps.cur.execute(sql, values)
psycopg2.ProgrammingError: syntax error at or near "%"
LINE 3:               VALUES (%s,%s,%s,%s,%s)
                              ^

看来Psycopg2无法将我的变量绑定到％s参数，但我无法弄清楚原因。非常感谢任何帮助或想法！

Answer 1

当为我的查询构建参数标记时，我只需要在每个'前面有一个％。这有点令人困惑，因为Python中的旧字符串格式化方法也使用了％符号，但与Psycopg2不同。请参阅下面的工作代码（仅在'parameters'变量中更改）：

ps.cur = psycopg_cursor

def load_lists(list_of_lists, table):
    # Get number of columns in table
    sql = """
          SELECT column_name FROM information_schema.columns
          WHERE table_schema = 'public'
          AND table_name = '{}'
          """.format(table)
    ps.cur.execute(sql)
    columns_list = [i[0] for i in ps.cur.fetchall()]
    # Insert list of lists into table
    columns = '(' + ','.join(columns_list) + ')'
    parameters = '(' + ','.join(['%s' for i in columns_list]) + ')' # <--- THIS LINE
    for i in list_of_lists:
        sql = """
              INSERT INTO {} {}
              VALUES {}
              """.format(table, columns, parameters)
        values = tuple([j for j in i])
        ps.cur.execute(sql, values)

具有可变数量参数的Psycopg2查询会引发语法错误

1 个答案: