Question

在python + psycopg2中，可以转换使用内联for循环的这行代码：

args_str = ','.join(cur_psql.mogrify("(%(customer_id)s, %(customer_name)s, %(contact_name)s, %(address)s, %(city)s, %(postal_code)s, %(country)s)", row) for row in cur_msql)

在迭代for循环时，允许进行更多操作的一段代码，但仍然获得相同的输出（包含所有数据的单个对象 - ＆gt; args_str）？例如：

for row in cur_msql:
  # additional operations eg.:
  if row['customer_name'] == NULL:
    row['customer_name'] = row['customer_name']
  args_str =+ ','.join(cur_psql.mogrify("(%(customer_id)s, %(customer_name)s, %(contact_name)s, %(address)s, %(city)s, %(postal_code)s, %(country)s)", row)

Answer 1

此代码累积在每个＆＃34; mogrified＆＃34;的列表中。值然后使用join()将它们组合在一起：

args = []
for row in cur_msql:
    # additional operations eg.:
    if row['customer_name'] == NULL:
        row['customer_name'] = row['customer_name']
    args.append(cur_psql.mogrify("(%(customer_id)s, %(customer_name)s, %(contact_name)s, %(address)s, %(city)s, %(postal_code)s, %(country)s)", row))

args_str = ','.join(args)

它应该创建一个等效的args_str来：

args_str = ','.join(cur_psql.mogrify("(%(customer_id)s, %(customer_name)s, %(contact_name)s, %(address)s, %(city)s, %(postal_code)s, %(country)s)", row) for row in cur_msql)

（N.B。我在上面将x更改为row。）

该字符串实际上是否是您需要/想要的另一个问题。

Python - Concat输出的join（）方法

1 个答案: