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
   

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2. Seb
   • @elbaschid
   • Living in Vancouver !
   • Python Engineer at Eventbase
   

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3. Why This Talk?
   

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4. Terminology
   https://www.flickr.com/photos/chris_schultz/11306328493
   

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5. Parameter
   • Argument
   • Option
   

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6. Argument
   • Mandatory parameter
   • Only values required
   What It Looks Like:
   $ pgcli postgresql://....
   

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7. Option
   • Optional parameter
   • Name and value required
   What It Looks Like:
   $ heroku --help
   $ heroku logs --app my-heroku-app
   

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8. (Sub-)Command
   • Nested commands allowed
   • Groups sub-commands
   • Has options & arguments
   What It Looks Like:
   $ pip install django
   

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9. In Plain Python
   https://www.flickr.com/photos/tutam/5008073062/
   

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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))
    

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11. The Limitations
    • Manual parsing
    • No input validation
    • No help text formatting
    

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12. Choose A Library
    https://www.flickr.com/photos/14601516@N00/3778738056
    

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13. Standard Library
    • optparse
    • argparse
    

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14. There Are Others
    • docopt
    • clint
    • ...many more...
    

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15. Introducing Click
    https://www.flickr.com/photos/27587002@N07/7155464950
    

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16. click
    • Author: Armin Ronacher
    • Version 6.x
    • http://click.pocoo.org/6/
    

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17. click
    • Intuitive
    • Nestable and composable
    • Better handling of input and output
    • Why Click?
    

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18. Let's Build A CLI
    https://www.flickr.com/photos/31381897@N03/3967634792
    

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19. pip install click
    

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20. Setting Up A CLI
    https://www.flickr.com/photos/sveinhal/2416609728
    

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21. On Github
    • Click Template: https://github.com/elbaschid/cc-python-cli
    • Example Code: bit.ly/pycon-click-example
    

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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
    

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23. Decorator-based approach
    # my_!_tool/cli.py
    import click
    @click.command()
    def main():
    click.secho('I am the my_!_tool CLI', fg='blue')
    

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24. Our Example
    https://www.flickr.com/photos/judy-van-der-velden/14687818499
    

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25. Ad Notifications
    • Parsing a given search URL
    • Extracting ads
    • Ignore "seen" ads
    • Email notifications
    

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26. Specify a URL
    

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27. Run it!
    $ ad_notifier "http://www.pinkbike.com/buysell/..."
    Processing URL: http://www.pinkbike.com/buysell/list/...
    Found 20 ads!
    

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28. Arguments
    https://www.flickr.com/photos/alper/2781645509
    

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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)))
    

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30. Send an Notification Email
    

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31. Run it!
    $ ad_notifier "http://..." --email my@email.com
    Processing URL: http://...
    Found 20 ads!
    Sending email to my@email.com
    

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32. Options
    https://www.flickr.com/photos/photographingtravis/15427838493
    

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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)
    

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34. Handle New Ads Only
    

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35. Run it!
    $ ad_notifier "http://..."
    ...
    Found 0 ads!
    $ ad_notifier "http://..." --reset-cache
    ...
    Found 20 ads!
    

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36. Flags
    https://www.flickr.com/photos/pennstatelive/16216912657
    

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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)))
    ...
    

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38. Make it a Periodic Task
    

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39. Run it!
    $ # With scheduler
    $ ad_notifier run_periodically \
    --run-every 5 --email my@email.com
    $ # Once
    $ ad_notifier run_once \
    --email my@email.com
    

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40. (Sub-)Commands
    (https://www.flickr.com/photos/soldiersmediacenter/5754070333)
    

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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
    

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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):
    ...
    

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43. Context
    https://www.flickr.com/photos/chanceprojects/16286089602
    

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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}
    

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45. Updating Sub-Commands
    @main.command()
    @click.pass_context
    def run_once(context):
    process_url(**context.obj)
    

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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)
    

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47. The Final Command
    $ # With scheduler
    $ ad_notifier run_periodically \
    --run-every 5 --email my@email.com
    $ # Once
    $ ad_notifier run_once \
    --email my@email.com
    

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48. ! We Did It !
    

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49. Improve Documentation
    

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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
    

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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.
    """
    

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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...
    

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53. Also Check Out
    • Environment Variables
    • Parameter Types
    • Testing
    • Bash Autocomplete
    

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54. Questions?
    https://www.flickr.com/photos/thomashawk/9058066607
    

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55. Click
    A Pleasure To Write
    A Pleasure To Use
    Sebastian Vetter
    @elbaschid
    Slides: http://bit.ly/click-slides
    

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