小编Shh*_*Shh的帖子

这只是为了学术兴趣.我经历了很多以下情况.

either_true = False
if x:
  ...do something1
  either_true = True
elif y:
  ...do something2
  either_true = True
if either_true:
  ..do something3

是否有任何pythonic方式,或通常更好的编程方式.基本上只有当或者elif为真时才执行something3.

我是django和web开发的新手.在创建超级用户时从"Django的权威指南"中学习我得到以下错误(OS mac10.8.2&django1.4.3)

Would you like to create one now? (yes/no): yes
Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/Library/Python/2.7/site-packages/django/core/management/__init__.py", line 443, in execute_from_command_line
    utility.execute()
  File "/Library/Python/2.7/site-packages/django/core/management/__init__.py", line 382, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Library/Python/2.7/site-packages/django/core/management/base.py", line 196, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/Library/Python/2.7/site-packages/django/core/management/base.py", line 232, in execute
    output = self.handle(*args, **options)
  File "/Library/Python/2.7/site-packages/django/core/management/base.py", line 371, in handle
    return self.handle_noargs(**options)
  File "/Library/Python/2.7/site-packages/django/core/management/commands/syncdb.py", line 110, in handle_noargs
    emit_post_sync_signal(created_models, verbosity, interactive, db)
  File "/Library/Python/2.7/site-packages/django/core/management/sql.py", line 189, in emit_post_sync_signal
    interactive=interactive, …

我有两张桌子

table 1
col1 date
1    13/4/2014
2    15/4/2014
3    17/4/2014
5    19/4/2014

table 2
col1 date
1    13/4/2014
3    16/4/2014
6    18/4/2014

joining the two tables i should get

col1 date       col2 date
1    13/4/2014  1    13/4/2014
2    15/4/2014
3    17/4/2014  3    16/4/2014
                6    18/4/2014
5    19/4/2014

重要的是date列应该排序,可以看到col数据6和5.这可能吗？

编辑:最后的表需要被命令col1.date并col2.date使得提前无论是在col1或col2将在连接表进行排序18/4/2014会之前,19/4/2014即使他们是在不同的列.我希望我明白我的观点.谢谢编辑:

table 1
1, "2014-04-03" 
2, "2014-04-04"
3, "2014-04-11"
4, "2014-04-16" …

假设我们有两套:

t = {('b', 3), ('a', 2)}
r = {('b', 4), ('c', 6)}

我希望第一个元素上的联合导致

u = {('b', 3), ('a', 2), ('c', 6)}

如果两个地方都存在重复的符号(例如上面的例子'b'),那么应该保留第一个列表的元素.谢谢.