A corpus view is a class wrapper around a corpus file that reads in blocks of tokens as needed. Its purpose is to provide a view into a file without reading the whole file at once (since corpus files can often be quite large). If the corpus readers included by NLTK already meet all your needs, then you do not have to know anything about corpus views. But, if you have a custom file format that needs special handling, this recipe will show you how to create and use a custom corpus view. The main corpus view class is StreamBackedCorpusView, which opens a single file as a stream, and maintains an internal cache of blocks it has read.

Blocks of tokens are read in with a block reader function. A block can be any piece of text, such as a paragraph or a line, and tokens are parts of a block, such as individual words. In the Creating a part-of-speech tagged word corpus recipe, we discussed the default para_block_reader function of the TaggedCorpusReader class, which reads...