django - from django.db.models import F - class F

# Tintin filed a news story!
reporter = Reporters.objects.get(name='Tintin')
reporter.stories_filed += 1
reporter.save()

# 等于

from django.db.models import F
reporter = Reporters.objects.get(name='Tintin')
reporter.stories_filed = F('stories_filed') + 1
reporter.save()

Reporter.objects.all().update(stories_filed=F('stories_filed') + 1)

F() therefore can offer performance advantages by:

getting the database, rather than Python, to do work
reducing the number of queries some operations require

提供了性能优势：
getting方法，也就是查询操作，更快
减少了某些操作的大量查询

你看这事情弄得多蛋疼？
原本SQL直接执行就爽得不行，偏要搞一层又一层，还不如直接上！