Updating file properties

31 Jul

These techniques are useful in many areas, and tagging gives us a simple context in which to present them.

We will also see how tagging is the second step in the typical NLP pipeline, following tokenization.

Understanding why such words are tagged as they are in each context can help us clarify the distinctions between the tags.

is an association between a word and a part-of-speech tag.

Notice that they are not in the same order they were originally entered; this is because dictionaries are not sequences but mappings (cf. Alternatively, to just find the keys, we can convert the dictionary to a list If we try to access a key that is not in a dictionary, we get an error.

However, its often useful if a dictionary can automatically create an entry for this new key and give it a default value, such as zero or the empty list.

Many of these categories arise from superficial analysis the distribution of words in text.Most often, we are mapping from a "word" to some structured object.For example, a document index maps from a word (which we can represent as a string), to a list of pages (represented as a list of integers).Note that part-of-speech tags have been converted to uppercase, since this has become standard practice since the Brown Corpus was published.Tagged corpora for several other languages are distributed with NLTK, including Chinese, Hindi, Portuguese, Spanish, Dutch and Catalan.