Skip to main content

Docopt is amazing

I love the command line and I love Python. So, naturally, I am an avid user of the argparse module bundled with Python. Today I discovered docopt and I am so totally converted. argparse is great but there is a bunch of setup code that you have to write and often things look very boilerplate-y and messy and it just looks like there should be a more concise way of expressing the command line interface to a program. Enter docopt

docopt allows you to describe your commandline interface in your doc string and then it parses this description and creates a command line parser that returns a dictionary with the values for all the options filled in. Just like that.

So, for example, one of my scripts has a docstring that looks like

Usage:
  compute_eye_epoch [-R DATAROOT] [-x EXCEL] [-d DATABASE] [-e EPOCH] [-f|-F] [-q]

Options:
  -h --help     Show this screen and exit.
  -R DATAROOT   Root of data directory [default: ../../Data]
  -x EXCEL      Spreadsheet with sessions/trials etc [default: ../../Notes/sessions_and_neurons.xlsx]
  -d DATABASE   sqlite3 database we write to [default: test.sqlite3]
  -e EPOCH      Name of epoch we want to process
  -f            Force recomputation of all entries for this epoch
  -F            Force storing of epoch (automatically forces recomputation)
  -q            Quiet mode (print only ERROR level logger messages)

And the __main__ part of the code is

import docopt

if __name__ == '__main__':
  arguments = docopt.docopt(__doc__, version='v1')
  print arguments

If I call the program with -h then I get the usage information printed and the program exits. If I call it with other options args will be filled out, for example:

{'-F': False,
 '-R': '../../Data',
 '-d': 'test.sqlite3',
 '-e': None,
 '-f': False,
 '-q': False,
 '-x': '../../Notes/sessions_and_neurons.xlsx'}

This totally removes the barrier to creating command line interfaces and removes clutter from the __main__ section of the code! Amazing! Give it a try!
Labels:

Comments

Post a Comment

Popular posts from this blog

A note on Python's __exit__() and errors

Python's context managers are a very neat way of handling code that needs a teardown once you are done. Python objects have do have a destructor method ( __del__ ) called right before the last instance of the object is about to be destroyed. You can do a teardown there. However there is a lot of fine print to the __del__ method. A cleaner way of doing tear-downs is through Python's context manager , manifested as the with keyword. class CrushMe: def __init__(self): self.f = open('test.txt', 'w') def foo(self, a, b): self.f.write(str(a - b)) def __enter__(self): return self def __exit__(self, exc_type, exc_val, exc_tb): self.f.close() return True with CrushMe() as c: c.foo(2, 3) One thing that is important, and that got me just now, is error handling. I made the mistake of ignoring all those 'junk' arguments ( exc_type, exc_val, exc_tb ). I just skimmed the docs and what popped out is that you need to return True or
Post a Comment
Read more

Using adminer on Mac OS X

adminer is a nice php based sqlite manager. I prefer the firefox plugin "sqlite manager" but it currently has a strange issue with FF5 that basically makes it unworkable, so I was looking for an alternative to tide me over. I really don't want apache running all the time on my computer and don't want people browsing to my computer, so what I needed to do was: Download the adminer php script into /Library/WebServer/Documents/ Change /etc/apache2/httpd.conf to allow running of php scripts (uncomment the line that begins: LoadModule php5_module Start the apache server: sudo apachectl -k start Operate the script by going to localhost Stop the server: sudo apachectl -k stop  
Post a Comment
Read more