一个经典的python字典生成式案例

 1 @lru_cache.lru_cache(maxsize=None)
 2 def get_commands():
 3     """
 4     Returns a dictionary mapping command names to their callback applications.
 5 
 6     This works by looking for a management.commands package in django.core, and
 7     in each installed application -- if a commands package exists, all commands
 8     in that package are registered.
 9 
10     Core commands are always included. If a settings module has been
11     specified, user-defined commands will also be included.
12 
13     The dictionary is in the format {command_name: app_name}. Key-value
14     pairs from this dictionary can then be used in calls to
15     load_command_class(app_name, command_name)
16 
17     If a specific version of a command must be loaded (e.g., with the
18     startapp command), the instantiated module can be placed in the
19     dictionary in place of the application name.
20 
21     The dictionary is cached on the first call and reused on subsequent
22     calls.
23     """
24     commands = {name: ‘django.core‘ for name in find_commands(upath(__path__[0]))}
25 
26     if not settings.configured:
27         return commands
28 
29     for app_config in reversed(list(apps.get_app_configs())):
30         path = os.path.join(app_config.path, ‘management‘)
31         commands.update({name: app_config.name for name in find_commands(path)})
32 
33     return commands