%% Author: Fred L. Drake, Jr. \section{Standard Module \module{pprint}} \declaremodule{standard}{pprint} \modulesynopsis{Data pretty printer.} The \module{pprint} module provides a capability to ``pretty-print'' arbitrary Python data structures in a form which can be used as input to the interpreter. If the formatted structures include objects which are not fundamental Python types, the representation may not be loadable. This may be the case if objects such as files, sockets, classes, or instances are included, as well as many other builtin objects which are not representable as Python constants. The formatted representation keeps objects on a single line if it can, and breaks them onto multiple lines if they don't fit within the allowed width. Construct \class{PrettyPrinter} objects explicitly if you need to adjust the width constraint. The \module{pprint} module defines one class: % First the implementation class: \begin{classdesc}{PrettyPrinter}{...} Construct a \class{PrettyPrinter} instance. This constructor understands several keyword parameters. An output stream may be set using the \var{stream} keyword; the only method used on the stream object is the file protocol's \method{write()} method. If not specified, the \class{PrettyPrinter} adopts \code{sys.stdout}. Three additional parameters may be used to control the formatted representation. The keywords are \var{indent}, \var{depth}, and \var{width}. The amount of indentation added for each recursive level is specified by \var{indent}; the default is one. Other values can cause output to look a little odd, but can make nesting easier to spot. The number of levels which may be printed is controlled by \var{depth}; if the data structure being printed is too deep, the next contained level is replaced by \samp{...}. By default, there is no constraint on the depth of the objects being formatted. The desired output width is constrained using the \var{width} parameter; the default is eighty characters. If a structure cannot be formatted within the constrained width, a best effort will be made. \begin{verbatim} >>> import pprint, sys >>> stuff = sys.path[:] >>> stuff.insert(0, stuff[:]) >>> pp = pprint.PrettyPrinter(indent=4) >>> pp.pprint(stuff) [ [ '', '/usr/local/lib/python1.5', '/usr/local/lib/python1.5/test', '/usr/local/lib/python1.5/sunos5', '/usr/local/lib/python1.5/sharedmodules', '/usr/local/lib/python1.5/tkinter'], '', '/usr/local/lib/python1.5', '/usr/local/lib/python1.5/test', '/usr/local/lib/python1.5/sunos5', '/usr/local/lib/python1.5/sharedmodules', '/usr/local/lib/python1.5/tkinter'] >>> >>> import parser >>> tup = parser.ast2tuple( ... parser.suite(open('pprint.py').read()))[1][1][1] >>> pp = pprint.PrettyPrinter(depth=6) >>> pp.pprint(tup) (266, (267, (307, (287, (288, (...)))))) \end{verbatim} \end{classdesc} % Now the derivative functions: The \class{PrettyPrinter} class supports several derivative functions: \begin{funcdesc}{pformat}{object} Return the formatted representation of \var{object} as a string. The default parameters for formatting are used. \end{funcdesc} \begin{funcdesc}{pprint}{object\optional{, stream}} Prints the formatted representation of \var{object} on \var{stream}, followed by a newline. If \var{stream} is omitted, \code{sys.stdout} is used. This may be used in the interactive interpreter instead of a \keyword{print} statement for inspecting values. The default parameters for formatting are used. \begin{verbatim} >>> stuff = sys.path[:] >>> stuff.insert(0, stuff) >>> pprint.pprint(stuff) [, '', '/usr/local/lib/python1.5', '/usr/local/lib/python1.5/test', '/usr/local/lib/python1.5/sunos5', '/usr/local/lib/python1.5/sharedmodules', '/usr/local/lib/python1.5/tkinter'] \end{verbatim} \end{funcdesc} \begin{funcdesc}{isreadable}{object} Determine if the formatted representation of \var{object} is ``readable,'' or can be used to reconstruct the value using \function{eval()}\bifuncindex{eval}. This always returns false for recursive objects. \begin{verbatim} >>> pprint.isreadable(stuff) 0 \end{verbatim} \end{funcdesc} \begin{funcdesc}{isrecursive}{object} Determine if \var{object} requires a recursive representation. \end{funcdesc} One more support function is also defined: \begin{funcdesc}{saferepr}{object} Return a string representation of \var{object}, protected against recursive data structures. If the representation of \var{object} exposes a recursive entry, the recursive reference will be represented as \samp{}. The representation is not otherwise formatted. \end{funcdesc} % This example is outside the {funcdesc} to keep it from running over % the right margin. \begin{verbatim} >>> pprint.saferepr(stuff) "[, '', '/usr/local/lib/python1.5', '/usr/loca l/lib/python1.5/test', '/usr/local/lib/python1.5/sunos5', '/usr/local/lib/python 1.5/sharedmodules', '/usr/local/lib/python1.5/tkinter']" \end{verbatim} \subsection{PrettyPrinter Objects} \label{PrettyPrinter Objects} \class{PrettyPrinter} instances have the following methods: \begin{methoddesc}{pformat}{object} Return the formatted representation of \var{object}. This takes into Account the options passed to the \class{PrettyPrinter} constructor. \end{methoddesc} \begin{methoddesc}{pprint}{object} Print the formatted representation of \var{object} on the configured stream, followed by a newline. \end{methoddesc} The following methods provide the implementations for the corresponding functions of the same names. Using these methods on an instance is slightly more efficient since new \class{PrettyPrinter} objects don't need to be created. \begin{methoddesc}{isreadable}{object} Determine if the formatted representation of the object is ``readable,'' or can be used to reconstruct the value using \function{eval()}\bifuncindex{eval}. Note that this returns false for recursive objects. If the \var{depth} parameter of the \class{PrettyPrinter} is set and the object is deeper than allowed, this returns false. \end{methoddesc} \begin{methoddesc}{isrecursive}{object} Determine if the object requires a recursive representation. \end{methoddesc}