python - Python: creating a comma separated string from a query

Question

I have a query

 messages = Message.objects.all()

I want to create a Create a comma separated string of all numbers from message.number

This is what I have tried:

number = ""
for obj in messages:
     number = number + "," + obj.number

How can I do this? PS this string can be VERY long over 400,000 numbers!

Answer 1

使用join()：

",".join(str(msg.number) for msg in Message.objects.all())

此外，由于您有一个很大的查询集，请考虑使用查询集迭代器将结果分成块。有关更多信息，请参阅：

• 为什么遍历大型 Django QuerySet 会消耗大量内存？
• 限制 *Large* Django QuerySet 中的内存使用
• http://djangosnippets.org/snippets/1949/
• http://djangosnippets.org/snippets/1170/

Answer 2

使用str.join：

number = ','.join(messages)