Click - PyCaribbean 2017 - Puerto Rico

Transcript

1. Click A Pleasure To Write A Pleasure To Use Sebastian Vetter @elbaschid Slides: http://bit.ly/click-slides
2. Seb • @elbaschid • Living in Vancouver ! • Python Engineer at Eventbase
3. Why This Talk?
4. Terminology https://www.flickr.com/photos/chris_schultz/11306328493
5. Parameter • Argument • Option
6. Argument • Mandatory parameter • Only values required What It Looks Like: $ pgcli postgresql://....
7. Option • Optional parameter • Name and value required What It Looks Like: $ heroku --help $ heroku logs --app my-heroku-app
8. (Sub-)Command • Nested commands allowed • Groups sub-commands • Has options & arguments What It Looks Like: $ pip install django
9. In Plain Python https://www.flickr.com/photos/tutam/5008073062/
10. Most Basic CLI import sys if len(sys.argv) <= 1: print('You need to give me an argument') sys.exit(1) args = sys.argv[1:] print('Your argument are: {}'.format(args))
11. The Limitations • Manual parsing • No input validation • No help text formatting
12. Choose A Library https://www.flickr.com/photos/14601516@N00/3778738056
13. Standard Library • optparse • argparse
14. There Are Others • docopt • clint • ...many more...
15. Introducing Click https://www.flickr.com/photos/27587002@N07/7155464950
16. click • Author: Armin Ronacher • Version 6.x • http://click.pocoo.org/6/
17. click • Intuitive • Nestable and composable • Better handling of input and output • Why Click?
18. Let's Build A CLI https://www.flickr.com/photos/31381897@N03/3967634792
19. pip install click
20. Setting Up A CLI https://www.flickr.com/photos/sveinhal/2416609728
21. On Github • Click Template: https://github.com/elbaschid/cc-python-cli • Example Code: bit.ly/pycon-click-example
22. Create A Project $ pip install cookiecutter $ cookiecutter https://github.com/elbaschid/cc-python-cli ... $ cd my-!-tool $ pip install -e . $ my_!_tool I am the my_!_tool CLI
23. Decorator-based approach # my_!_tool/cli.py import click @click.command() def main(): click.secho('I am the my_!_tool CLI', fg='blue')
24. Our Example https://www.flickr.com/photos/judy-van-der-velden/14687818499
25. Ad Notifications • Parsing a given search URL • Extracting ads • Ignore "seen" ads • Email notifications
26. Specify a URL
27. Run it! $ ad_notifier "http://www.pinkbike.com/buysell/..." Processing URL: http://www.pinkbike.com/buysell/list/... Found 20 ads!
28. Arguments https://www.flickr.com/photos/alper/2781645509
29. Add an argument # ad_notifier/cli.py @click.command() @click.argument('url') def main(url): click.echo('Processing URL:', url) ads = find_ads(url) click.echo('Found {} ads!'.format(len(ads)))
30. Send an Notification Email
31. Run it! $ ad_notifier "http://..." --email my@email.com Processing URL: http://... Found 20 ads! Sending email to my@email.com
32. Options https://www.flickr.com/photos/photographingtravis/15427838493
33. Add Email Option @click.command() @click.argument('url') @click.option('--email', envvar='EMAIL_ADDRESS') def main(url, email): ... if email and ads: send_email(email, ads)
34. Handle New Ads Only
35. Run it! $ ad_notifier "http://..." ... Found 0 ads! $ ad_notifier "http://..." --reset-cache ... Found 20 ads!
36. Flags https://www.flickr.com/photos/pennstatelive/16216912657
37. Reset the cache @click.command() ... @click.option('--reset-cache', default=False, is_flag=True) def main(url, email, reset_cache): click.echo('Processing URL:', url) new_ads = find_new_ads(url, reset_cache) click.echo('Found {} ads!'.format(len(new_ads))) ...
38. Make it a Periodic Task
39. Run it! $ # With scheduler $ ad_notifier run_periodically <URL> \ --run-every 5 --email my@email.com $ # Once $ ad_notifier run_once <URL> \ --email my@email.com
40. (Sub-)Commands (https://www.flickr.com/photos/soldiersmediacenter/5754070333)
41. Add a run & schedule command @click.group() def main(): pass @main.command() ... def run_once(url, email, reset_cache): pass @main.command() ... @click.option('--run-every', default=5, type=int) def run_periodically(..., run_every): pass
42. Not Very DRY @main.command() @click.argument('url') @click.option('--email') @click.option('--reset-cache', default=False, is_flag=True) def run_once(url, email, reset_cache): ... @main.command() @click.argument('url') @click.option('--email') @click.option('--reset-cache', default=False, is_flag=True) @click.option('--run-every', default=5, type=int) def run_periodically(url, email, reset_cache, run_every): ...
43. Context https://www.flickr.com/photos/chanceprojects/16286089602
44. Using the Context obj @click.group() @click.argument('url') @click.option('--email') @click.option('--reset-cache', ...) @click.pass_context def main(context, url, email, reset_cache): context.obj = { 'url': url, 'email': email, 'reset_cache': reset_cache}
45. Updating Sub-Commands @main.command() @click.pass_context def run_once(context): process_url(**context.obj)
46. Add schedule subcommand @main.command() @click.option('--run-every', default=5, type=int) @click.pass_context def run_periodically(context, run_every): schedule.every(run_every).minutes.do( process_url, **context.obj) while True: schedule.run_pending() time.sleep(1)
47. The Final Command $ # With scheduler $ ad_notifier <URL> run_periodically \ --run-every 5 --email my@email.com $ # Once $ ad_notifier <URL> run_once \ --email my@email.com
48. ! We Did It !
49. Improve Documentation
50. No Effort $ ad_notifier Usage: ad_notifier [OPTIONS] URL COMMAND [ARGS]... Options: --email TEXT --reset-cache --help Show this message and exit. Commands: run_once run_periodically
51. Adding help text @click.option('--reset-cache', default=False, is_flag=True, help='reset the internal ads cache') @click.pass_context def main(context, url, email, reset_cache): """ Check pinkbike ads for URL and (optionally) send email notification. """
52. A Little Effort $ ad_notifier Usage: ad_notifier [OPTIONS] URL COMMAND [ARGS]... Check pinkbike ads for URL and (optionally) send email notification. Options: --email TEXT email to send notifications to --reset-cache reset the internal ads cache --help Show this message and exit. Commands: run_once Run check for new ads once. run_periodically Run scheduler to check for new ads...
53. Also Check Out • Environment Variables • Parameter Types • Testing • Bash Autocomplete
54. Questions? https://www.flickr.com/photos/thomashawk/9058066607
55. Click A Pleasure To Write A Pleasure To Use Sebastian Vetter @elbaschid Slides: http://bit.ly/click-slides