#  Author:      Fred L. Drake, Jr.

#               fdrake@acm.org

#

#  This is a simple little module I wrote to make life easier.  I didn't

#  see anything quite like it in the library, though I may have overlooked

#  something.  I wrote this when I was trying to read some heavily nested

#  tuples with fairly non-descriptive content.  This is modeled very much

#  after Lisp/Scheme - style pretty-printing of lists.  If you find it

#  useful, thank small children who sleep at night.

"""Support to pretty-print lists, tuples, & dictionaries recursively.

Very simple, but useful, especially in debugging data structures.

Classes

-------

PrettyPrinter()

    Handle pretty-printing operations onto a stream using a configured

    set of formatting parameters.

Functions

---------

pformat()

    Format a Python object into a pretty-printed representation.

pprint()

    Pretty-print a Python object to a stream [default is sys.stdout].

saferepr()

    Generate a 'standard' repr()-like value, but protect against recursive

    data structures.

"""

import sys as _sys

from cStringIO import StringIO as _StringIO

__all__ = ["pprint","pformat","isreadable","isrecursive","saferepr",

           "PrettyPrinter"]

# cache these for faster access:

_commajoin = ", ".join

_id = id

_len = len

_type = type

def pprint(object, stream=None, indent=1, width=80, depth=None):

    """Pretty-print a Python object to a stream [default is sys.stdout]."""

    printer = PrettyPrinter(

        stream=stream, indent=indent, width=width, depth=depth)

    printer.pprint(object)

def pformat(object, indent=1, width=80, depth=None):

    """Format a Python object into a pretty-printed representation."""

    return PrettyPrinter(indent=indent, width=width, depth=depth).pformat(object)

def saferepr(object):

    """Version of repr() which can handle recursive data structures."""

    return _safe_repr(object, {}, None, 0)[0]

def isreadable(object):

    """Determine if saferepr(object) is readable by eval()."""

    return _safe_repr(object, {}, None, 0)[1]

def isrecursive(object):

    """Determine if object requires a recursive representation."""

    return _safe_repr(object, {}, None, 0)[2]

class PrettyPrinter:

    def __init__(self, indent=1, width=80, depth=None, stream=None):

        """Handle pretty printing operations onto a stream using a set of

        configured parameters.

        indent

            Number of spaces to indent for each level of nesting.

        width

            Attempted maximum number of columns in the output.

        depth

            The maximum depth to print out nested structures.

        stream

            The desired output stream.  If omitted (or false), the standard

            output stream available at construction will be used.

        """

        indent = int(indent)

        width = int(width)

        assert indent >= 0, "indent must be >= 0"

        assert depth is None or depth > 0, "depth must be > 0"

        assert width, "width must be != 0"

        self._depth = depth

        self._indent_per_level = indent

        self._width = width

        if stream is not None:

            self._stream = stream

        else:

            self._stream = _sys.stdout

    def pprint(self, object):

        self._format(object, self._stream, 0, 0, {}, 0)

        self._stream.write("\n")

    def pformat(self, object):

        sio = _StringIO()

        self._format(object, sio, 0, 0, {}, 0)

        return sio.getvalue()

    def isrecursive(self, object):

        return self.format(object, {}, 0, 0)[2]

    def isreadable(self, object):

        s, readable, recursive = self.format(object, {}, 0, 0)

        return readable and not recursive

    def _format(self, object, stream, indent, allowance, context, level):

        level = level + 1

        objid = _id(object)

        if objid in context:

            stream.write(_recursion(object))

            self._recursive = True

            self._readable = False

            return

        rep = self._repr(object, context, level - 1)

        typ = _type(object)

        sepLines = _len(rep) > (self._width - 1 - indent - allowance)

        write = stream.write

        if sepLines:

            r = getattr(typ, "__repr__", None)

            if issubclass(typ, dict) and r is dict.__repr__:

                write('{')

                if self._indent_per_level > 1:

                    write((self._indent_per_level - 1) * ' ')

                length = _len(object)

                if length:

                    context[objid] = 1

                    indent = indent + self._indent_per_level

                    items  = object.items()

                    items.sort()

                    key, ent = items[0]

                    rep = self._repr(key, context, level)

                    write(rep)

                    write(': ')

                    self._format(ent, stream, indent + _len(rep) + 2,

                                  allowance + 1, context, level)

                    if length > 1:

                        for key, ent in items[1:]:

                            rep = self._repr(key, context, level)

                            write(',\n%s%s: ' % (' '*indent, rep))

                            self._format(ent, stream, indent + _len(rep) + 2,

                                          allowance + 1, context, level)

                    indent = indent - self._indent_per_level

                    del context[objid]

                write('}')

                return

            if (issubclass(typ, list) and r is list.__repr__) or \

               (issubclass(typ, tuple) and r is tuple.__repr__):

                if issubclass(typ, list):

                    write('[')

                    endchar = ']'

                else:

                    write('(')

                    endchar = ')'

                if self._indent_per_level > 1:

                    write((self._indent_per_level - 1) * ' ')

                length = _len(object)

                if length:

                    context[objid] = 1

                    indent = indent + self._indent_per_level

                    self._format(object[0], stream, indent, allowance + 1,

                                 context, level)

                    if length > 1:

                        for ent in object[1:]:

                            write(',\n' + ' '*indent)

                            self._format(ent, stream, indent,

                                          allowance + 1, context, level)

                    indent = indent - self._indent_per_level

                    del context[objid]

                if issubclass(typ, tuple) and length == 1:

                    write(',')

                write(endchar)

                return

        write(rep)

    def _repr(self, object, context, level):

        repr, readable, recursive = self.format(object, context.copy(),

                                                self._depth, level)

        if not readable:

            self._readable = False

        if recursive:

            self._recursive = True

        return repr

    def format(self, object, context, maxlevels, level):

        """Format object for a specific context, returning a string

        and flags indicating whether the representation is 'readable'

        and whether the object represents a recursive construct.

        """

        return _safe_repr(object, context, maxlevels, level)

# Return triple (repr_string, isreadable, isrecursive).

def _safe_repr(object, context, maxlevels, level):

    typ = _type(object)

    if typ is str:

        if 'locale' not in _sys.modules:

            return repr(object), True, False

        if "'" in object and '"' not in object:

            closure = '"'

            quotes = {'"': '\\"'}

        else:

            closure = "'"

            quotes = {"'": "\\'"}

        qget = quotes.get

        sio = _StringIO()

        write = sio.write

        for char in object:

            if char.isalpha():

                write(char)

            else:

                write(qget(char, repr(char)[1:-1]))

        return ("%s%s%s" % (closure, sio.getvalue(), closure)), True, False

    r = getattr(typ, "__repr__", None)

    if issubclass(typ, dict) and r is dict.__repr__:

        if not object:

            return "{}", True, False

        objid = _id(object)

        if maxlevels and level > maxlevels:

            return "{...}", False, objid in context

        if objid in context:

            return _recursion(object), False, True

        context[objid] = 1

        readable = True

        recursive = False

        components = []

        append = components.append

        level += 1

        saferepr = _safe_repr

        for k, v in sorted(object.items()):

            krepr, kreadable, krecur = saferepr(k, context, maxlevels, level)

            vrepr, vreadable, vrecur = saferepr(v, context, maxlevels, level)

            append("%s: %s" % (krepr, vrepr))

            readable = readable and kreadable and vreadable

            if krecur or vrecur:

                recursive = True

        del context[objid]

        return "{%s}" % _commajoin(components), readable, recursive

    if (issubclass(typ, list) and r is list.__repr__) or \

       (issubclass(typ, tuple) and r is tuple.__repr__):

        if issubclass(typ, list):

            if not object:

                return "[]", True, False

            format = "[%s]"

        elif _len(object) == 1:

            format = "(%s,)"

        else:

            if not object:

                return "()", True, False

            format = "(%s)"

        objid = _id(object)

        if maxlevels and level > maxlevels:

            return format % "...", False, objid in context

        if objid in context:

            return _recursion(object), False, True

        context[objid] = 1

        readable = True

        recursive = False

        components = []

        append = components.append

        level += 1

        for o in object:

            orepr, oreadable, orecur = _safe_repr(o, context, maxlevels, level)

            append(orepr)

            if not oreadable:

                readable = False

            if orecur:

                recursive = True

        del context[objid]

        return format % _commajoin(components), readable, recursive

    rep = repr(object)

    return rep, (rep and not rep.startswith('<')), False

def _recursion(object):

    return ("<Recursion on %s with id=%s>"

            % (_type(object).__name__, _id(object)))

def _perfcheck(object=None):

    import time

    if object is None:

        object = [("string", (1, 2), [3, 4], {5: 6, 7: 8})] * 100000

    p = PrettyPrinter()

    t1 = time.time()

    _safe_repr(object, {}, None, 0)

    t2 = time.time()

    p.pformat(object)

    t3 = time.time()

    print "_safe_repr:", t2 - t1

    print "pformat:", t3 - t2

if __name__ == "__main__":

    _perfcheck()