小编gab*_*rtv的帖子

在Python中,可以读取字典/散列键,同时将键设置为默认值(如果尚不存在).

例如:

>>> d={'key': 'value'}
>>> d.setdefault('key', 'default')
'value'                                          # returns the existing value
>>> d.setdefault('key-doesnt-exist', 'default')
'default'                                        # sets and returns default value
>>> d
{'key-doesnt-exist': 'default', 'key': 'value'}

有没有相当于Ruby哈希？如果没有,Ruby中的惯用方法是什么？

在我看来,Ubuntu EC2镜像可能存在问题.经过一次新的apt-get更新后,我发布了这个:

$ apt-get install -yq git
E: Unable to locate package git

再过几次apt-get,它往往会成功.

使用VirtualBox 4.3.4和Vagrant 1.3.5.运行带有3.8内核的Ubuntu 12.04.3盒子:

# uname -a
Linux precise64 3.8.0-34-generic #49~precise1-Ubuntu SMP Wed Nov 13 18:05:00 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

尝试编译客户添加失败:

# /etc/init.d/vboxadd setup
Removing existing VirtualBox DKMS kernel modules ...done.
Removing existing VirtualBox non-DKMS kernel modules ...done.
Building the VirtualBox Guest Additions kernel modules
The headers for the current running kernel were not found. If the following
module compilation fails then this could be the reason.

Building the main Guest Additions module ...fail!
(Look at /var/log/vboxadd-install.log to …

Celery工作正常,有一天,命令行工作人员未能启动以下跟踪:

Traceback (most recent call last):
  File "/home/buildslave/venv/bin/celery", line 9, in <module>
    load_entry_point('celery==3.0.7', 'console_scripts', 'celery')()
  File "/home/buildslave/venv/local/lib/python2.7/site-packages/celery/__main__.py", line 14, in main
    main()
  File "/home/buildslave/venv/local/lib/python2.7/site-packages/celery/bin/celery.py", line 942, in main
    cmd.execute_from_commandline(argv)
  File "/home/buildslave/venv/local/lib/python2.7/site-packages/celery/bin/celery.py", line 886, in execute_from_commandline
    super(CeleryCommand, self).execute_from_commandline(argv)))
  File "/home/buildslave/venv/local/lib/python2.7/site-packages/celery/bin/base.py", line 175, in execute_from_commandline
    return self.handle_argv(prog_name, argv[1:])
  File "/home/buildslave/venv/local/lib/python2.7/site-packages/celery/bin/celery.py", line 881, in handle_argv
    return self.execute(command, argv)
  File "/home/buildslave/venv/local/lib/python2.7/site-packages/celery/bin/celery.py", line 856, in execute
    return cls(app=self.app).run_from_argv(self.prog_name, argv)
  File "/home/buildslave/venv/local/lib/python2.7/site-packages/celery/bin/celery.py", line 142, in run_from_argv
    return self(*args, **options)
  File "/home/buildslave/venv/local/lib/python2.7/site-packages/celery/bin/celery.py", line 112, in __call__
    ret …