annotate flagReader.py @ 1:59288b38ea7b

moved usage samples back to googlepages
author catherine@DellZilla.myhome.westell.com
date Wed, 05 Mar 2008 12:25:21 -0500
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1 """Defines and parses UNIX-style flags to modify command arguments.
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2
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3 print flagReader.FlagSet.parse.__doc__ for usage examples.
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4 """
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5
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6 import re
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7
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8 class Flag(object):
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9 def __init__(self, name, abbrev=None, nargs=0):
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10 """Flag(name, abbrev=None, nargs=0) : Defines a flag.
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11
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12 name: the full name of the flag (double-dash form)
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13 abbrev: the single-letter abbreviated form of the flag; defaults to
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14 nargs: number of arguments expected after the flag"""
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15
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16 self.name = name
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17 self.abbrev = abbrev or name[0]
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18 self.fullabbrev = '-%s' % (self.abbrev)
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19 self.fullname = '--%s' % (name)
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20 self.nargs = nargs
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21
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22 class FlagSet(object):
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23 def __init__(self, flags):
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24 if not issubclass(type(flags), list):
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25 raise TypeError, 'Argument must be a list'
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26 self.flags = flags
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27 self.lookup = {}
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28 for flag in self.flags:
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29 self.lookup[flag.abbrev] = flag
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30 self.lookup[flag.fullabbrev] = flag
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31 self.lookup[flag.fullname] = flag
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32 self.abbrevPattern = re.compile('^-([%s]+)$' % (''.join(f.abbrev for f in flags)))
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33 def parse(self, arg):
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34 """
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35 Finds flags; returns {flag: (values, if any)} and the remaining argument.
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36
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37 >>> f = FlagSet([Flag('foo'), Flag('bar'), Flag('gimmea', nargs=1)])
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38 >>> f.parse('-fb')
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39 ({'foo': [], 'bar': []}, '')
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40 >>> f.parse('no flags')
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41 ({}, 'no flags')
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42 >>> f.parse('-f blah')
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43 ({'foo': []}, 'blah')
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44 >>> f.parse('--bar')
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45 ({'bar': []}, '')
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46 >>> f.parse('--bar -f')
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47 ({'foo': [], 'bar': []}, '')
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48 >>> f.parse('--notaflag')
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49 ({}, '--notaflag')
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50 >>> f.parse('')
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51 ({}, '')
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52 >>> f.parse('--gimmea bee -f and then some other stuff')
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53 ({'gimmea': ['bee'], 'foo': []}, 'and then some other stuff')
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54 >>> f.parse('hidden -bar')
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55 ({}, 'hidden -bar')
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56 >>> f.parse('-g myarg -b')
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57 ({'gimmea': ['myarg'], 'bar': []}, '')
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58 """
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59 result = {}
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60 words = arg.split()
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61 while words:
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62 word = words[0]
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63 flag = self.lookup.get(word)
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64 if flag:
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65 result[flag.name] = []
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66 words.pop(0)
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67 for arg in range(flag.nargs):
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68 try:
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69 result[flag.name].append(words.pop(0))
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70 except IndexError: # there aren't as many args as we expect
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71 raise IndexError, '%s expects %d arguments' % (word, flag.nargs)
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72 continue # on to next word
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73 smashedAbbrevs = self.abbrevPattern.search(word)
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74 if smashedAbbrevs:
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75 for abbrev in smashedAbbrevs.group(1):
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76 result[self.lookup[abbrev].name] = []
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77 words.pop(0)
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78 continue # on to next word
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79 #if you get to here, word[0] does not denote options
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80 break
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81 return result, ' '.join(words)
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82
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83 def _test():
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84 import doctest
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85 doctest.testmod()
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86
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87 if __name__ == '__main__':
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88 _test()