# 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 self._depth and level > self._depth:
 write(rep)
 return

 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)
 if sepLines:
 write(',\n%s%s: ' % (' '*indent, rep))
 else:
 write(', %s: ' % 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__) or
 (issubclass(typ, set) and r is set.__repr__) or
 (issubclass(typ, frozenset) and r is frozenset.__repr__)
 ):
 length = _len(object)
 if issubclass(typ, list):
 write('[')
 endchar = ']'
 elif issubclass(typ, set):
 if not length:
 write('set()')
 return
 write('set([')
 endchar = '])'
 object = sorted(object)
 indent += 4
 elif issubclass(typ, frozenset):
 if not length:
 write('frozenset()')
 return
 write('frozenset([')
 endchar = '])'
 object = sorted(object)
 indent += 10
 else:
 write('(')
 endchar = ')'
 if self._indent_per_level > 1 and sepLines:
 write((self._indent_per_level - 1) * ' ')
 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:]:
 if sepLines:
 write(',\n' + ' '*indent)
 else:
 write(', ')
 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()