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%% Call Python from MATLAB
% These examples show how to use Python(R) language
% functions and modules within MATLAB(R). The first example calls a
% text-formatting module from the Python standard library. The
% second example shows how to use a third-party module,
% <http://www.crummy.com/software/BeautifulSoup/ Beautiful Soup>.
% If you want to run that example, follow the guidelines
% in the step for installing the module.
%
% MATLAB supports the reference implementation of Python,
% often called CPython, versions 2.7, 3.3, and 3.4.
% If you are on a Mac or Linux platform, you already have
% Python installed. If you are on Windows, you need to install
% a distribution, such as those found at <https://www.python.org/download>,
% if you have not already done so. For more information, see
% <docid:matlab_external.bujjwjn>.
%
% Copyright 2014 The MathWorks, Inc.
%% Call a Python Function to Wrap Text in a Paragraph
% MATLAB has equivalencies for much of the
% <http://docs.python.org/2/library/ Python standard library>, but not
% everything. For example, |textwrap| is a module for
% formatting blocks of text with carriage returns and other conveniences.
% MATLAB also provides a |textwrap| function, but it only wraps text to fit
% inside a UI control.
%%
% Create a paragraph of text to play with.
T = 'MATLAB(R) is a high-level language and interactive environment for numerical computation, visualization, and programming. Using MATLAB, you can analyze data, develop algorithms, and create models and applications. The language, tools, and built-in math functions enable you to explore multiple approaches and reach a solution faster than with spreadsheets or traditional programming languages, such as C/C++ or Java(TM).';
%% Convert a Python String to a MATLAB String
% Call the |textwrap.wrap| function by typing the characters |py.| in front
% of the function name. Do not type |import textwrap|.
wrapped = py.textwrap.wrap(T);
whos wrapped
%%
% |wrapped| is a Python list, which is a list of Python strings.
% MATLAB shows this type as |py.list|.
%%
% Convert |py.list| to
% a cell array of Python strings.
wrapped = cell(wrapped);
whos wrapped
%%
% Although |wrapped| is a MATLAB cell array,
% each cell element is a Python string.
wrapped{1}
%%
% Convert the Python strings to MATLAB strings using the |char| function.
wrapped = cellfun(@char, wrapped, 'UniformOutput', false);
wrapped{1}
%%
% Now each cell element is a MATLAB string.
%% Customize the Paragraph
% Customize the output of the paragraph using keyword arguments.
%
% The previous code uses the |wrap| convenience
% function, but the module provides many more options using the
% |py.textwap.TextWrapper| functionality.
% To use the options, call |py.textwap.TextWrapper| with
% keyword arguments described at
% <https://docs.python.org/2/library/textwrap.html#textwrap.TextWrapper>.
%
% Create keyword arguments using the MATLAB |pyargs| function with
% a comma-separated list of name/value pairs. |width| formats
% the text to be 30 characters wide. The |initial_indent| and
% |subsequent_indent|
% keywords begin each line with the comment character, |%|, used by
% MATLAB.
tw = py.textwrap.TextWrapper(pyargs(...
'initial_indent', '% ', ...
'subsequent_indent', '% ', ...
'width', int32(30)));
wrapped = wrap(tw,T);
%%
% Convert to a MATLAB argument and display the results.
wrapped = cellfun(@char, cell(wrapped), 'UniformOutput', false);
fprintf('%s\n', wrapped{:})
%% Use Beautiful Soup, a Third-Party Python Module
% This example shows how to use a third-party
% module, <http://www.crummy.com/software/BeautifulSoup/ Beautiful Soup>,
% a tool for parsing HTML. If you want to run the example, you need
% to install this module using |apt-get|, |pip|, |easy_install|, or other
% tool you use to install Python modules.
%
% First, find a Web page that includes a table of data. This example uses a
% table of the population of the world from the following
% English-language Wikipedia site.
% This example assumes the first table contains the population data,
% and assumes the country name is in the second column
% and the third column contains the population.
html = webread('http://en.wikipedia.org/wiki/List_of_countries_by_population');
soup = py.bs4.BeautifulSoup(html,'html.parser');
%%
% Next, extract all of the table data from the HTML, creating a cell
% array. If you want a deeper understanding of
% what is happening, refer to the
% <http://www.crummy.com/software/BeautifulSoup/bs4/doc/
% documentation for Beautiful Soup>.
tables = soup.find_all('table');
t = cell(tables);
%%
% The first table is the one of interest; extract its rows.
c = cell(t{1}.find_all('tr'));
c = cell(c)';
%%
% Now loop over the cell array, extracting the country name and population
% from each row, found in the second and third columns respectively.
countries = cell(size(c));
populations = nan(size(c));
for i = 1:numel(c)
row = c{i};
row = cell(row.find_all('td'));
if ~isempty(row)
countries{i} = char(row{2}.get_text());
populations(i) = str2double(char(row{3}.get_text()));
end
end
%%
% Finally, create a MATLAB table from the data, and eliminate any
% lingering |nan| values; these NaNs represented invalid rows when
% importing the HTML.
data = table(countries, populations, ...
'VariableNames', {'Country', 'Population'});
data = data(~isnan(data.Population), :);
%%
% Trim the tail end of the table and make a pie chart
restofWorldPopulation = sum(data.Population(11:end));
data = data(1:10, :);
data = [data;table({' Rest of World'}, restofWorldPopulation, ...
'VariableNames', {'Country', 'Population'})]
pie(data.Population)
legend(data.Country, 'Location', 'EastOutside');
title('Distribution of World Population')
%% Learn More
%
% It is sufficient to remember that
% Python is yet another potential source of libraries for the MATLAB
% user. If you want to learn about moving data between MATLAB and
% Python, including Python data types such as tuples and dictionaries,
% see <docid:matlab_doccenter.buik_wp-1>.
%