\section{\module{pprint} ---         Data pretty printer} \declaremodule{standard}{pprint}\modulesynopsis{Data pretty printer.}\moduleauthor{Fred L. Drake, Jr.}{fdrake@acm.org}\sectionauthor{Fred L. Drake, Jr.}{fdrake@acm.org}  The \module{pprint} module provides a capability to ``pretty-print''arbitrary Python data structures in a form which can be used as inputto the interpreter.  If the formatted structures include objects whichare not fundamental Python types, the representation may not beloadable.  This may be the case if objects such as files, sockets,classes, or instances are included, as well as many other builtinobjects 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 theallowed width.  Construct \class{PrettyPrinter} objects explicitly ifyou need to adjust the width constraint. \versionchanged[Dictionaries are sorted by key before the display iscomputed; before 2.5, a dictionary was sorted only if its displayrequired more than one line, although that wasn't documented]{2.5} The \module{pprint} module defines one class:  % First the implementation class: \begin{classdesc}{PrettyPrinter}{...}Construct a \class{PrettyPrinter} instance.  This constructorunderstands several keyword parameters.  An output stream may be setusing the \var{stream} keyword; the only method used on the streamobject is the file protocol's \method{write()} method.  If notspecified, the \class{PrettyPrinter} adopts \code{sys.stdout}.  Threeadditional parameters may be used to control the formattedrepresentation.  The keywords are \var{indent}, \var{depth}, and\var{width}.  The amount of indentation added for each recursive levelis specified by \var{indent}; the default is one.  Other values cancause output to look a little odd, but can make nesting easier tospot.  The number of levels which may be printed is controlled by\var{depth}; if the data structure being printed is too deep, the nextcontained level is replaced by \samp{...}.  By default, there is noconstraint on the depth of the objects being formatted.  The desiredoutput width is constrained using the \var{width} parameter; thedefault is eighty characters.  If a structure cannot be formattedwithin 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\optional{, indent\optional{,width\optional{, depth}}}}Return the formatted representation of \var{object} as a string.  \var{indent},\var{width} and \var{depth} will be passed to the \class{PrettyPrinter}constructor as formatting parameters.\versionchanged[The parameters \var{indent}, \var{width} and \var{depth}were added]{2.4}\end{funcdesc} \begin{funcdesc}{pprint}{object\optional{, stream\optional{,indent\optional{, width\optional{, depth}}}}}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.    \var{indent},\var{width} and \var{depth} will be passed to the \class{PrettyPrinter}constructor as formatting parameters. \begin{verbatim}>>> stuff = sys.path[:]>>> stuff.insert(0, stuff)>>> pprint.pprint(stuff)[<Recursion on list with id=869440>, '', '/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}\versionchanged[The parameters \var{indent}, \var{width} and \var{depth}were added]{2.4}\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 forrecursive objects. \begin{verbatim}>>> pprint.isreadable(stuff)False\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 againstrecursive data structures.  If the representation of \var{object}exposes a recursive entry, the recursive reference will be representedas \samp{<Recursion on \var{typename} with id=\var{number}>}.  Therepresentation 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)"[<Recursion on list with id=682968>, '', '/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}  \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 intoaccount the options passed to the \class{PrettyPrinter} constructor.\end{methoddesc} \begin{methoddesc}{pprint}{object}Print the formatted representation of \var{object} on the configuredstream, followed by a newline.\end{methoddesc} The following methods provide the implementations for thecorresponding functions of the same names.  Using these methods on aninstance 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 forrecursive 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} This method is provided as a hook to allow subclasses to modify theway objects are converted to strings.  The default implementation usesthe internals of the \function{saferepr()} implementation. \begin{methoddesc}{format}{object, context, maxlevels, level}Returns three values: the formatted version of \var{object} as astring, a flag indicating whether the result is readable, and a flagindicating whether recursion was detected.  The first argument is theobject to be presented.  The second is a dictionary which contains the\function{id()} of objects that are part of the current presentationcontext (direct and indirect containers for \var{object} that areaffecting the presentation) as the keys; if an object needs to bepresented which is already represented in \var{context}, the thirdreturn value should be true.  Recursive calls to the \method{format()}method should add additional entries for containers to thisdictionary.  The third argument, \var{maxlevels}, gives the requestedlimit to recursion; this will be \code{0} if there is no requestedlimit.  This argument should be passed unmodified to recursive calls.The fourth argument, \var{level}, gives the current level; recursivecalls should be passed a value less than that of the current call.\versionadded{2.3}\end{methoddesc}