matplotlib Code

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\language english
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\begin_layout Section
Dictionaries for counting words
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\begin_layout Standard
A common task in text processing is to produce a count of word frequencies.
 While NumPy has a builtin histogram function for doing numerical histograms,
 it won't work out of the box for couting discrete items, since it is a
 binning histogram for a range of real values.
\end_layout

\begin_layout Standard
But the Python language provides very powerful string manipulation capabilities,
 as well as a very flexible and efficiently implemented builtin data type,
 the 
\emph on
dictionary
\emph default
, that makes this task a very simple one.
\end_layout

\begin_layout Standard
In this problem, you will need to count the frequencies of all the words
 contained in a compressed text file supplied as input.
 
\end_layout

\begin_layout Standard
The listing\InsetSpace ~

\begin_inset LatexCommand \ref{code:wordfreqs_skel}

\end_inset

 contains a skeleton for this problem, with 
\family typewriter
XXX
\family default
 marking various places that are incomplete.
 
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\begin_layout Standard
\begin_inset ERT
status open

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\backslash
lstinputlisting[label=code:wordfreqs_skel,caption={IGNORED}]{skel/wordfreqs_skel.
py}
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\end_inset


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\begin_layout Subsection*
Hints
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\begin_layout Itemize
The 
\family typewriter
print_vk 
\family default
function is already provided for you as a simple way to summarize your results.
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\begin_layout Itemize
You will need to read the compressed file 
\family typewriter
HISTORY.gz
\family default
.
 Python has facilities to do this without having to manually uncompress
 it.
\end_layout

\begin_layout Itemize
Consider `words' simply the result of splitting the input text into a list,
 using any form of whitespace as a separator.
 This is obviously a very na´ve definition of `word', but it shall suffice
 for the purposes of this exercise.
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\begin_layout Itemize
Python strings have a 
\family typewriter
.split()
\family default
 method that allows for very flexible splitting.
 You can easily get more details on it in IPython:
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status open

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\backslash
begin{lstlisting}
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In [2]: a = 'somestring'
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In [3]: a.split?
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Type:           builtin_function_or_method
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Base Class:     <type 'builtin_function_or_method'>
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Namespace:      Interactive
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Docstring:
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    S.split([sep [,maxsplit]]) -> list of strings
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\begin_layout Standard

\end_layout

\begin_layout Standard

    Return a list of the words in the string S, using sep as the
\end_layout

\begin_layout Standard

    delimiter string.
  If maxsplit is given, at most maxsplit
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    splits are done.
 If sep is not specified or is None, any
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    whitespace string is a separator.
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\backslash
end{lstlisting}
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\end_inset


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\begin_layout Standard
The complete set of methods of Python strings can be viewed by hitting the
 TAB key in IPython after typing `
\family typewriter
a.
\family default
', and each of them can be similarly queried with the `
\family typewriter
?
\family default
' operator as above.
 For more details on Python strings and their companion sequence types,
 see 
\begin_inset LatexCommand \htmlurl{http://docs.python.org/lib/typesseq.html}

\end_inset

.
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