main.py
The main application is defined in main.py:
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35 | import sys
from cliff.app import App
from cliff.commandmanager import CommandManager
class DemoApp(App):
def __init__(self):
super(DemoApp, self).__init__(
description='cliff demo app',
version='0.1',
command_manager=CommandManager('cliff.demo'),
deferred_help=True,
)
def initialize_app(self, argv):
self.LOG.debug('initialize_app')
def prepare_to_run_command(self, cmd):
self.LOG.debug('prepare_to_run_command %s', cmd.__class__.__name__)
def clean_up(self, cmd, result, err):
self.LOG.debug('clean_up %s', cmd.__class__.__name__)
if err:
self.LOG.debug('got an error: %s', err)
def main(argv=sys.argv[1:]):
myapp = DemoApp()
return myapp.run(argv)
if __name__ == '__main__':
sys.exit(main(sys.argv[1:]))
|
The DemoApp class inherits from App and overrides
__init__() to set the program description and version number. It also
passes a CommandManager instance configured to look for plugins in the
cliff.demo namespace.
The initialize_app() method of DemoApp will be invoked after the
main program arguments are parsed, but before any command processing is
performed and before the application enters interactive mode. This hook is
intended for opening connections to remote web services, databases, etc. using
arguments passed to the main application.
The prepare_to_run_command() method of DemoApp will be invoked
after a command is identified, but before the command is given its arguments
and run. This hook is intended for pre-command validation or setup that must be
repeated and cannot be handled by initialize_app().
The clean_up() method of DemoApp is invoked after a command
runs. If the command raised an exception, the exception object is passed to
clean_up(). Otherwise the err argument is None.
The main() function defined in main.py is registered as a console
script entry point so that DemoApp can be run from the command line
(see the discussion of setup.py below).
simple.py
Two commands are defined in simple.py:
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24 | import logging
from cliff.command import Command
class Simple(Command):
"A simple command that prints a message."
log = logging.getLogger(__name__)
def take_action(self, parsed_args):
self.log.info('sending greeting')
self.log.debug('debugging')
self.app.stdout.write('hi!\n')
class Error(Command):
"Always raises an error"
log = logging.getLogger(__name__)
def take_action(self, parsed_args):
self.log.info('causing error')
raise RuntimeError('this is the expected exception')
|
Simple demonstrates using logging to emit messages on the console at
different verbose levels:
(.venv)$ cliffdemo simple
sending greeting
hi!
(.venv)$ cliffdemo -v simple
prepare_to_run_command Simple
sending greeting
debugging
hi!
clean_up Simple
(.venv)$ cliffdemo -q simple
hi!
Error always raises a RuntimeError exception when it is
invoked, and can be used to experiment with the error handling features of
cliff:
(.venv)$ cliffdemo error
causing error
ERROR: this is the expected exception
(.venv)$ cliffdemo -v error
prepare_to_run_command Error
causing error
ERROR: this is the expected exception
clean_up Error
got an error: this is the expected exception
(.venv)$ cliffdemo --debug error
causing error
this is the expected exception
Traceback (most recent call last):
File ".../cliff/app.py", line 218, in run_subcommand
result = cmd.run(parsed_args)
File ".../cliff/command.py", line 43, in run
self.take_action(parsed_args)
File ".../demoapp/cliffdemo/simple.py", line 24, in take_action
raise RuntimeError('this is the expected exception')
RuntimeError: this is the expected exception
Traceback (most recent call last):
File "/Users/dhellmann/Envs/cliff/bin/cliffdemo", line 9, in <module>
load_entry_point('cliffdemo==0.1', 'console_scripts', 'cliffdemo')()
File ".../demoapp/cliffdemo/main.py", line 33, in main
return myapp.run(argv)
File ".../cliff/app.py", line 160, in run
result = self.run_subcommand(remainder)
File ".../cliff/app.py", line 218, in run_subcommand
result = cmd.run(parsed_args)
File ".../cliff/command.py", line 43, in run
self.take_action(parsed_args)
File ".../demoapp/cliffdemo/simple.py", line 24, in take_action
raise RuntimeError('this is the expected exception')
RuntimeError: this is the expected exception
list.py
list.py includes a single command derived from cliff.lister.Lister
which prints a list of the files in the current directory.
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18 | import logging
import os
from cliff.lister import Lister
class Files(Lister):
"""Show a list of files in the current directory.
The file name and size are printed by default.
"""
log = logging.getLogger(__name__)
def take_action(self, parsed_args):
return (('Name', 'Size'),
((n, os.stat(n).st_size) for n in os.listdir('.'))
)
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Files prepares the data, and Lister manages the output
formatter and printing the data to the console:
(.venv)$ cliffdemo files
+---------------+------+
| Name | Size |
+---------------+------+
| build | 136 |
| cliffdemo.log | 2546 |
| Makefile | 5569 |
| source | 408 |
+---------------+------+
(.venv)$ cliffdemo files -f csv
"Name","Size"
"build",136
"cliffdemo.log",2690
"Makefile",5569
"source",408
show.py
show.py includes a single command derived from cliff.show.ShowOne
which prints the properties of the named file.
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31 | import logging
import os
from cliff.show import ShowOne
class File(ShowOne):
"Show details about a file"
log = logging.getLogger(__name__)
def get_parser(self, prog_name):
parser = super(File, self).get_parser(prog_name)
parser.add_argument('filename', nargs='?', default='.')
return parser
def take_action(self, parsed_args):
stat_data = os.stat(parsed_args.filename)
columns = ('Name',
'Size',
'UID',
'GID',
'Modified Time',
)
data = (parsed_args.filename,
stat_data.st_size,
stat_data.st_uid,
stat_data.st_gid,
stat_data.st_mtime,
)
return (columns, data)
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File prepares the data, and ShowOne manages the output
formatter and printing the data to the console:
(.venv)$ cliffdemo file setup.py
+---------------+--------------+
| Field | Value |
+---------------+--------------+
| Name | setup.py |
| Size | 5825 |
| UID | 502 |
| GID | 20 |
| Modified Time | 1335569964.0 |
+---------------+--------------+
setup.py
The demo application is packaged using setuptools.
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71 | #!/usr/bin/env python
PROJECT = 'cliffdemo'
# Change docs/sphinx/conf.py too!
VERSION = '0.1'
from setuptools import setup, find_packages
try:
long_description = open('README.rst', 'rt').read()
except IOError:
long_description = ''
setup(
name=PROJECT,
version=VERSION,
description='Demo app for cliff',
long_description=long_description,
author='Doug Hellmann',
author_email='doug.hellmann@gmail.com',
url='https://github.com/openstack/cliff',
download_url='https://github.com/openstack/cliff/tarball/master',
classifiers=['Development Status :: 3 - Alpha',
'License :: OSI Approved :: Apache Software License',
'Programming Language :: Python',
'Programming Language :: Python :: 2',
'Programming Language :: Python :: 2.7',
'Programming Language :: Python :: 3',
'Programming Language :: Python :: 3.2',
'Intended Audience :: Developers',
'Environment :: Console',
],
platforms=['Any'],
scripts=[],
provides=[],
install_requires=['cliff'],
namespace_packages=[],
packages=find_packages(),
include_package_data=True,
entry_points={
'console_scripts': [
'cliffdemo = cliffdemo.main:main'
],
'cliff.demo': [
'simple = cliffdemo.simple:Simple',
'two_part = cliffdemo.simple:Simple',
'error = cliffdemo.simple:Error',
'list files = cliffdemo.list:Files',
'files = cliffdemo.list:Files',
'file = cliffdemo.show:File',
'show file = cliffdemo.show:File',
'unicode = cliffdemo.encoding:Encoding',
'hooked = cliffdemo.hook:Hooked',
],
'cliff.demo.hooked': [
'sample-hook = cliffdemo.hook:Hook',
],
},
zip_safe=False,
)
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The important parts of the packaging instructions are the entry_points
settings. All of the commands are registered in the cliff.demo namespace.
Each main program should define its own command namespace so that it only loads
the command plugins that it should be managing.
