Class FeatureDictReader

object --+    
         |    
      dict --+
             |
            FeatureDictReader

Utility class to dencode data feature vectors (represented as index:count lines in a text file) into a string:count feature dictionary objects. These were probably encoded in the first place with the matching "FeatureDictWriter" class. The basic strategy is to just back-translate the index numbers into the actual string representation features. This class (which extends the dict class) stores the index:feature mappings for subsequent access (note that this is the inverse of the FeatureDictWriter's feature:index mappings).

Note that this current implementation assumes the features are represented as simple text strings. If you want a more sophisticated object representation, you'll have to add your own layer above that can encode / decode the features into strings for storage in the plain text files.

>>> from cStringIO import StringIO
>>> infile = StringIO();        # doctest can't handle multi-line strings well
>>> print >> infile, "# 0 a"    # So write it out as a StringIO first
>>> print >> infile, "# 1 s"
>>> print >> infile, "# 2 d"
>>> print >> infile, "# 3 g"
>>> print >> infile, "# 4 f"
>>> print >> infile, "# 5 A"
>>> print >> infile, "# 6 F"
>>> print >> infile, "# 7 S"
>>> print >> infile, "# 8 D"
>>> print >> infile, "# 9 h"
>>> print >> infile, "# 10 G"
>>> print >> infile, "# 11 H"
>>> print >> infile, "asdfsdfg 0:1 1:2 2:2 3:1 4:2 "
>>> print >> infile, "asdfasdfASDF 0:2 1:2 2:2 4:2 5:1 6:1 7:1 8:1 "
>>> print >> infile, "dfghDFGH 2:1 3:1 4:1 6:1 8:1 9:1 10:1 11:1 "
>>> infile = StringIO(infile.getvalue());
>>>
>>> featureReader = FeatureDictReader(infile);
>>> # Read out and print the contents of each feature dictionary
>>> for (featureDict, description) in featureReader.iterFeatureDicts():
...     print description, str(featureDict)
asdfsdfg {'a': 1, 's': 2, 'd': 2, 'g': 1, 'f': 2}
asdfasdfASDF {'a': 2, 'A': 1, 'd': 2, 'F': 1, 'f': 2, 'S': 1, 's': 2, 'D': 1}
dfghDFGH {'D': 1, 'g': 1, 'F': 1, 'h': 1, 'f': 1, 'G': 1, 'H': 1, 'd': 1}