Natural Language Processing with Python

A Sample of Python Libraries

Python has hundreds of third-party libraries, specialized software packages that extend the functionality of Python. NLTK is one such library. To realize the full power of Python programming, you should become familiar with several other libraries. Most of these will need to be manually installed on your computer.

Matplotlib

Python has some libraries that are useful for visualizing language data. The Matplotlib package supports sophisticated plotting functions with a MATLAB-style interface, and is available from http://matplotlib.sourceforge.net/.

So far we have focused on textual presentation and the use of formatted print statements to get output lined up in columns. It is often very useful to display numerical data in graphical form, since this often makes it easier to detect patterns. For example, in Example 3-6, we saw a table of numbers showing the frequency of particular modal verbs in the Brown Corpus, classified by genre. The program in Example 4-12 presents the same information in graphical format. The output is shown in Figure 4-4 (a color figure in the graphical display).

Example 4-12. Frequency of modals in different sections of the Brown Corpus.

colors = 'rgbcmyk' # red, green, blue, cyan, magenta, yellow, black
def bar_chart(categories, words, counts):
    "Plot a bar chart showing counts for each word by category" import pylab ind = pylab.arange(len(words)) width = 1 / (len(categories) + 1) bar_groups = [] for c in range(len(categories)): bars ...