Python/ManyArgs

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Programmers spend much programming time doing maintenance on existing code. This snippet shows one way to handle a function that just keeps growing (without refactoring the code that uses it) in a nice flexible way

import datetime
"""
How to easily deal with many parameters in maintenance
The problem:
 - a function has grown to require many parameters, many with default values
 - the function is being maintained (and param list likely will grow)
The forces:
 - we want the defaults to be seen "all in one place" for self documentation
 - we may need to handle old positional parameters, also self documented
 - we want to allow the defaults to be defined outside the function def
 - we want speed and clarity
The answer: Use a dictionary of defaults
"""
def handleManyArgs(root,logdir,auths,**kwargs):
  # handle old positional parameters: Historic artifact
  # opportunity to spell the names nicely, self-document meaning
  kwargs["rootDirectory"] = root
  kwargs['logDirectory'] = logdir
  kwargs['authorizedUsers'] = auths
  # this dictionary will probably be from a configuration file or similar
  defaultArgs = {
    'alpha': 0,          # document this parameter
    'beta': 'usually',   # ditto
    'gamma': 'ray',      # ditto
    'delta': 12,         # etc
    'epsilon': 1.03e-12,
    'zeta': None,
    'eta': datetime.time(hour=11,minute=12,second=13),
    'theta': None,
    'etc': 'many more',
                 }
  for k,v in defaultArgs.items():
    kwargs.setdefault(k,v)

  print "All arguments:\n  %s"%("\n  ".join(["%s->%s"%(str(k),str(v)) for k,v in kwargs.items()]))
  
if __name__ == "__main__":  
  handleManyArgs("/","/tmp",['griswolf'])
  handleManyArgs("/","/tmp",['griswolf','daviddoria'],gamma='mary',theta=1.35)

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