Exploring the Demo App¶
The cliff source package includes a demoapp
directory containing an example
main program with several command plugins.
Setup¶
To install and experiment with the demo app you should create a virtual environment and activate it. This will make it easy to remove the app later, since it doesn’t do anything useful and you aren’t likely to want to hang onto it after you understand how it works:
$ pip install virtualenv
$ virtualenv .venv
$ . .venv/bin/activate
(.venv)$
Next, install cliff in the same environment:
(.venv)$ python setup.py install
Finally, install the demo application into the virtual environment:
(.venv)$ cd demoapp
(.venv)$ python setup.py install
Usage¶
Both cliff and the demo installed, you can now run the command cliffdemo
.
For basic command usage instructions and a list of the commands available from the plugins, run:
(.venv)$ cliffdemo -h
or:
(.venv)$ cliffdemo --help
Run the simple
command by passing its name as argument to cliffdemo
:
(.venv)$ cliffdemo simple
The simple
command prints this output to the console:
sending greeting
hi!
To see help for an individual command, use the help
command:
(.venv)$ cliffdemo help files
or the --help
option:
(.venv)$ cliffdemo files --help
For more information, refer to the autogenerated documentation below.
The Source¶
The cliffdemo
application is defined in a cliffdemo
package containing
several modules.
main.py¶
The main application is defined in main.py
:
1import sys
2
3from cliff.app import App
4from cliff.commandmanager import CommandManager
5
6
7class DemoApp(App):
8 def __init__(self):
9 super().__init__(
10 description='cliff demo app',
11 version='0.1',
12 command_manager=CommandManager('cliff.demo'),
13 deferred_help=True,
14 )
15
16 def initialize_app(self, argv):
17 self.LOG.debug('initialize_app')
18
19 def prepare_to_run_command(self, cmd):
20 self.LOG.debug('prepare_to_run_command %s', cmd.__class__.__name__)
21
22 def clean_up(self, cmd, result, err):
23 self.LOG.debug('clean_up %s', cmd.__class__.__name__)
24 if err:
25 self.LOG.debug('got an error: %s', err)
26
27
28def main(argv=sys.argv[1:]):
29 myapp = DemoApp()
30 return myapp.run(argv)
31
32
33if __name__ == '__main__':
34 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
:
1import logging
2
3from cliff.command import Command
4
5
6class Simple(Command):
7 "A simple command that prints a message."
8
9 log = logging.getLogger(__name__)
10
11 def take_action(self, parsed_args):
12 self.log.info('sending greeting')
13 self.log.debug('debugging')
14 self.app.stdout.write('hi!\n')
15
16
17class Error(Command):
18 "Always raises an error"
19
20 log = logging.getLogger(__name__)
21
22 def take_action(self, parsed_args):
23 self.log.info('causing error')
24 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.
1import logging
2import os
3
4from cliff.lister import Lister
5
6
7class Files(Lister):
8 """Show a list of files in the current directory.
9
10 The file name and size are printed by default.
11 """
12
13 log = logging.getLogger(__name__)
14
15 def take_action(self, parsed_args):
16 return (
17 ('Name', 'Size'),
18 ((n, os.stat(n).st_size) for n in os.listdir('.')),
19 )
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.
1import logging
2import os
3
4from cliff.show import ShowOne
5
6
7class File(ShowOne):
8 "Show details about a file"
9
10 log = logging.getLogger(__name__)
11
12 def get_parser(self, prog_name):
13 parser = super().get_parser(prog_name)
14 parser.add_argument('filename', nargs='?', default='.')
15 return parser
16
17 def take_action(self, parsed_args):
18 stat_data = os.stat(parsed_args.filename)
19 columns = (
20 'Name',
21 'Size',
22 'UID',
23 'GID',
24 'Modified Time',
25 )
26 data = (
27 parsed_args.filename,
28 stat_data.st_size,
29 stat_data.st_uid,
30 stat_data.st_gid,
31 stat_data.st_mtime,
32 )
33 return (columns, data)
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.
1#!/usr/bin/env python
2
3from setuptools import find_packages
4from setuptools import setup
5
6PROJECT = 'cliffdemo'
7
8# Change docs/sphinx/conf.py too!
9VERSION = '0.1'
10
11try:
12 long_description = open('README.rst').read()
13except OSError:
14 long_description = ''
15
16setup(
17 name=PROJECT,
18 version=VERSION,
19 description='Demo app for cliff',
20 long_description=long_description,
21 author='Doug Hellmann',
22 author_email='doug.hellmann@gmail.com',
23 url='https://github.com/openstack/cliff',
24 download_url='https://github.com/openstack/cliff/tarball/master',
25 classifiers=[
26 'Development Status :: 3 - Alpha',
27 'License :: OSI Approved :: Apache Software License',
28 'Programming Language :: Python',
29 'Programming Language :: Python :: 3',
30 'Programming Language :: Python :: 3 :: Only',
31 'Intended Audience :: Developers',
32 'Environment :: Console',
33 ],
34 platforms=['Any'],
35 scripts=[],
36 provides=[],
37 install_requires=['cliff'],
38 namespace_packages=[],
39 packages=find_packages(),
40 include_package_data=True,
41 entry_points={
42 'console_scripts': ['cliffdemo = cliffdemo.main:main'],
43 'cliff.demo': [
44 'simple = cliffdemo.simple:Simple',
45 'two_part = cliffdemo.simple:Simple',
46 'error = cliffdemo.simple:Error',
47 'list files = cliffdemo.list:Files',
48 'files = cliffdemo.list:Files',
49 'file = cliffdemo.show:File',
50 'show file = cliffdemo.show:File',
51 'unicode = cliffdemo.encoding:Encoding',
52 'hooked = cliffdemo.hook:Hooked',
53 ],
54 'cliff.demo.hooked': [
55 'sample-hook = cliffdemo.hook:Hook',
56 ],
57 },
58 zip_safe=False,
59)
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.
Command Extension Hooks¶
Individual subcommands of an application can be extended via hooks registered
as separate plugins. In the demo application, the hooked
command has a
single extension registered.
The namespace for hooks is a combination of the application namespace and the
command name. In this case, the application namespace is cliff.demo
and the
command is hooked
, so the extension namespace is cliff.demo.hooked
. If
the subcommand name includes spaces, they are replaced with underscores
(”_
”) to build the namespace.
1# All Rights Reserved.
2#
3# Licensed under the Apache License, Version 2.0 (the "License"); you may
4# not use this file except in compliance with the License. You may obtain
5# a copy of the License at
6#
7# http://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
11# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
12# License for the specific language governing permissions and limitations
13# under the License.
14
15import logging
16
17from cliff.command import Command
18from cliff.hooks import CommandHook
19
20
21class Hooked(Command):
22 "A command to demonstrate how the hooks work"
23
24 log = logging.getLogger(__name__)
25
26 def take_action(self, parsed_args):
27 self.app.stdout.write('this command has an extension\n')
28
29
30class Hook(CommandHook):
31 """Hook sample for the 'hooked' command.
32
33 This would normally be provided by a separate package from the
34 main application, but is included in the demo app for simplicity.
35
36 """
37
38 def get_parser(self, parser):
39 print('sample hook get_parser()')
40 parser.add_argument('--added-by-hook')
41 return parser
42
43 def get_epilog(self):
44 return 'extension epilog text'
45
46 def before(self, parsed_args):
47 self.cmd.app.stdout.write('before\n')
48
49 def after(self, parsed_args, return_code):
50 self.cmd.app.stdout.write('after\n')
Although the hooked
command does not add any arguments to the parser it
creates, the help output shows that the extension adds a single
--added-by-hook
option.
(.venv)$ cliffdemo hooked -h
sample hook get_parser()
usage: cliffdemo hooked [-h] [--added-by-hook ADDED_BY_HOOK]
A command to demonstrate how the hooks work
optional arguments:
-h, --help show this help message and exit
--added-by-hook ADDED_BY_HOOK
extension epilog text
(.venv)$ cliffdemo hooked
sample hook get_parser()
before
this command has an extension
after
See also
cliff.hooks.CommandHook
– The API for command hooks.
Autogenerated Documentation¶
The following documentation is generated using the following directive, which is provided by the cliff Sphinx extension.
.. autoprogram-cliff:: cliffdemo.main.DemoApp
:application: cliffdemo
.. autoprogram-cliff:: cliff.demo
:application: cliffdemo
Output¶
Global Options¶
cliff demo app
cliffdemo [--version] [-v | -q] [--log-file LOG_FILE] [--debug]
- --version¶
show program’s version number and exit
- -v, --verbose¶
Increase verbosity of output. Can be repeated.
- -q, --quiet¶
Suppress output except warnings and errors.
- --log-file <LOG_FILE>¶
Specify a file to log output. Disabled by default.
- --debug¶
Show tracebacks on errors.
Command Options¶
error¶
Always raises an error
cliffdemo error
file¶
Show details about a file
cliffdemo file
[-f {json,shell,table,value,yaml}]
[-c COLUMN]
[--noindent]
[--prefix PREFIX]
[--max-width <integer>]
[--fit-width]
[--print-empty]
[filename]
- -f <FORMATTER>, --format <FORMATTER>¶
the output format, defaults to table
- -c COLUMN, --column COLUMN¶
specify the column(s) to include, can be repeated to show multiple columns
- --noindent¶
whether to disable indenting the JSON
- --prefix <PREFIX>¶
add a prefix to all variable names
- --max-width <integer>¶
Maximum display width, <1 to disable. You can also use the CLIFF_MAX_TERM_WIDTH environment variable, but the parameter takes precedence.
- --fit-width¶
Fit the table to the display width. Implied if –max-width greater than 0. Set the environment variable CLIFF_FIT_WIDTH=1 to always enable
- --print-empty¶
Print empty table if there is no data to show.
- filename¶
files¶
Show a list of files in the current directory.
The file name and size are printed by default.
cliffdemo files
[-f {csv,json,table,value,yaml}]
[-c COLUMN]
[--quote {all,minimal,none,nonnumeric}]
[--noindent]
[--max-width <integer>]
[--fit-width]
[--print-empty]
[--sort-column SORT_COLUMN]
[--sort-ascending | --sort-descending]
- -f <FORMATTER>, --format <FORMATTER>¶
the output format, defaults to table
- -c COLUMN, --column COLUMN¶
specify the column(s) to include, can be repeated to show multiple columns
- --quote <QUOTE_MODE>¶
when to include quotes, defaults to nonnumeric
- --noindent¶
whether to disable indenting the JSON
- --max-width <integer>¶
Maximum display width, <1 to disable. You can also use the CLIFF_MAX_TERM_WIDTH environment variable, but the parameter takes precedence.
- --fit-width¶
Fit the table to the display width. Implied if –max-width greater than 0. Set the environment variable CLIFF_FIT_WIDTH=1 to always enable
- --print-empty¶
Print empty table if there is no data to show.
- --sort-column SORT_COLUMN¶
specify the column(s) to sort the data (columns specified first have a priority, non-existing columns are ignored), can be repeated
- --sort-ascending¶
sort the column(s) in ascending order
- --sort-descending¶
sort the column(s) in descending order
hooked¶
A command to demonstrate how the hooks work
cliffdemo hooked
list files¶
Show a list of files in the current directory.
The file name and size are printed by default.
cliffdemo list files
[-f {csv,json,table,value,yaml}]
[-c COLUMN]
[--quote {all,minimal,none,nonnumeric}]
[--noindent]
[--max-width <integer>]
[--fit-width]
[--print-empty]
[--sort-column SORT_COLUMN]
[--sort-ascending | --sort-descending]
- -f <FORMATTER>, --format <FORMATTER>¶
the output format, defaults to table
- -c COLUMN, --column COLUMN¶
specify the column(s) to include, can be repeated to show multiple columns
- --quote <QUOTE_MODE>¶
when to include quotes, defaults to nonnumeric
- --noindent¶
whether to disable indenting the JSON
- --max-width <integer>¶
Maximum display width, <1 to disable. You can also use the CLIFF_MAX_TERM_WIDTH environment variable, but the parameter takes precedence.
- --fit-width¶
Fit the table to the display width. Implied if –max-width greater than 0. Set the environment variable CLIFF_FIT_WIDTH=1 to always enable
- --print-empty¶
Print empty table if there is no data to show.
- --sort-column SORT_COLUMN¶
specify the column(s) to sort the data (columns specified first have a priority, non-existing columns are ignored), can be repeated
- --sort-ascending¶
sort the column(s) in ascending order
- --sort-descending¶
sort the column(s) in descending order
show file¶
Show details about a file
cliffdemo show file
[-f {json,shell,table,value,yaml}]
[-c COLUMN]
[--noindent]
[--prefix PREFIX]
[--max-width <integer>]
[--fit-width]
[--print-empty]
[filename]
- -f <FORMATTER>, --format <FORMATTER>¶
the output format, defaults to table
- -c COLUMN, --column COLUMN¶
specify the column(s) to include, can be repeated to show multiple columns
- --noindent¶
whether to disable indenting the JSON
- --prefix <PREFIX>¶
add a prefix to all variable names
- --max-width <integer>¶
Maximum display width, <1 to disable. You can also use the CLIFF_MAX_TERM_WIDTH environment variable, but the parameter takes precedence.
- --fit-width¶
Fit the table to the display width. Implied if –max-width greater than 0. Set the environment variable CLIFF_FIT_WIDTH=1 to always enable
- --print-empty¶
Print empty table if there is no data to show.
- filename¶
simple¶
A simple command that prints a message.
cliffdemo simple
two part¶
A simple command that prints a message.
cliffdemo two part
unicode¶
Show some unicode text
cliffdemo unicode
[-f {csv,json,table,value,yaml}]
[-c COLUMN]
[--quote {all,minimal,none,nonnumeric}]
[--noindent]
[--max-width <integer>]
[--fit-width]
[--print-empty]
[--sort-column SORT_COLUMN]
[--sort-ascending | --sort-descending]
- -f <FORMATTER>, --format <FORMATTER>¶
the output format, defaults to table
- -c COLUMN, --column COLUMN¶
specify the column(s) to include, can be repeated to show multiple columns
- --quote <QUOTE_MODE>¶
when to include quotes, defaults to nonnumeric
- --noindent¶
whether to disable indenting the JSON
- --max-width <integer>¶
Maximum display width, <1 to disable. You can also use the CLIFF_MAX_TERM_WIDTH environment variable, but the parameter takes precedence.
- --fit-width¶
Fit the table to the display width. Implied if –max-width greater than 0. Set the environment variable CLIFF_FIT_WIDTH=1 to always enable
- --print-empty¶
Print empty table if there is no data to show.
- --sort-column SORT_COLUMN¶
specify the column(s) to sort the data (columns specified first have a priority, non-existing columns are ignored), can be repeated
- --sort-ascending¶
sort the column(s) in ascending order
- --sort-descending¶
sort the column(s) in descending order