254 lines
8.3 KiB
Python
254 lines
8.3 KiB
Python
# Author: Fred L. Drake, Jr.
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# fdrake@cnri.reston.va.us, fdrake@acm.org
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#
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# This is a simple little module I wrote to make life easier. I didn't
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# see anything quite like it in the library, though I may have overlooked
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# something. I wrote this when I was trying to read some heavily nested
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# tuples with fairly non-descriptive content. This is modelled very much
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# after Lisp/Scheme - style pretty-printing of lists. If you find it
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# useful, thank small children who sleep at night.
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"""Support to pretty-print lists, tuples, & dictionaries recursively.
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Very simple, but useful, especially in debugging data structures.
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Classes
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-------
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PrettyPrinter()
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Handle pretty-printing operations onto a stream using a configured
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set of formatting parameters.
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Functions
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---------
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pformat()
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Format a Python object into a pretty-printed representation.
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pprint()
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Pretty-print a Python object to a stream [default is sys.sydout].
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saferepr()
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Generate a 'standard' repr()-like value, but protect against recursive
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data structures.
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"""
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from types import DictType, ListType, TupleType
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try:
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from cStringIO import StringIO
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except ImportError:
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from StringIO import StringIO
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def pprint(object, stream=None):
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"""Pretty-print a Python object to a stream [default is sys.sydout]."""
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printer = PrettyPrinter(stream=stream)
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printer.pprint(object)
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def pformat(object):
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"""Format a Python object into a pretty-printed representation."""
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return PrettyPrinter().pformat(object)
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def isreadable(object):
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"""Determine if saferepr(object) is readable by eval()."""
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return PrettyPrinter().isreadable(object)
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def isrecursive(object):
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"""Determine if object requires a recursive representation."""
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return PrettyPrinter().isrecursive(object)
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def saferepr(object):
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"""Version of repr() which can handle recursive data structures."""
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return _safe_repr(object, {})[0]
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class PrettyPrinter:
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def __init__(self, indent=1, width=80, depth=None, stream=None):
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"""Handle pretty printing operations onto a stream using a set of
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configured parameters.
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indent
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Number of spaces to indent for each level of nesting.
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width
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Attempted maximum number of columns in the output.
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depth
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The maximum depth to print out nested structures.
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stream
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The desired output stream. If omitted (or false), the standard
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output stream available at construction will be used.
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"""
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indent = int(indent)
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width = int(width)
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assert indent >= 0
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assert (not depth) or depth > 0, "depth may not be negative"
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assert width
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self.__depth = depth
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self.__indent_per_level = indent
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self.__width = width
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if stream:
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self.__stream = stream
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else:
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import sys
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self.__stream = sys.stdout
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def pprint(self, object):
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self.__stream.write(self.pformat(object) + "\n")
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def pformat(self, object):
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sio = StringIO()
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self.__format(object, sio, 0, 0, {}, 0)
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return sio.getvalue()
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def isrecursive(self, object):
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self.__recursive = 0
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self.pformat(object)
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return self.__recursive
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def isreadable(self, object):
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self.__recursive = 0
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self.__readable = 1
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self.pformat(object)
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return self.__readable and not self.__recursive
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def __format(self, object, stream, indent, allowance, context, level):
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level = level + 1
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if context.has_key(id(object)):
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object = _Recursion(object)
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self.__recursive = 1
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rep = self.__repr(object, context, level - 1)
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objid = id(object)
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context[objid] = 1
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typ = type(object)
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sepLines = len(rep) > (self.__width - 1 - indent - allowance)
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if sepLines and typ in (ListType, TupleType):
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# Pretty-print the sequence.
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stream.write((typ is ListType) and '[' or '(')
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if self.__indent_per_level > 1:
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stream.write((self.__indent_per_level - 1) * ' ')
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length = len(object)
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if length:
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indent = indent + self.__indent_per_level
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self.__format(object[0], stream, indent, allowance + 1,
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context, level)
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if len(object) > 1:
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for ent in object[1:]:
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stream.write(',\n' + ' '*indent)
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self.__format(ent, stream, indent,
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allowance + 1, context, level)
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indent = indent - self.__indent_per_level
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if typ is TupleType and length == 1:
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stream.write(',')
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stream.write(((typ is ListType) and ']') or ')')
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elif sepLines and typ is DictType:
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stream.write('{')
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if self.__indent_per_level > 1:
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stream.write((self.__indent_per_level - 1) * ' ')
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length = len(object)
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if length:
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indent = indent + self.__indent_per_level
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items = object.items()
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items.sort()
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key, ent = items[0]
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rep = self.__repr(key, context, level) + ': '
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stream.write(rep)
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self.__format(ent, stream, indent + len(rep),
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allowance + 1, context, level)
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if len(items) > 1:
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for key, ent in items[1:]:
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rep = self.__repr(key, context, level) + ': '
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stream.write(',\n' + ' '*indent + rep)
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self.__format(ent, stream, indent + len(rep),
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allowance + 1, context, level)
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indent = indent - self.__indent_per_level
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stream.write('}')
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else:
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stream.write(rep)
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del context[objid]
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def __repr(self, object, context, level):
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repr, readable = _safe_repr(object, context, self.__depth, level)
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if not readable:
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self.__readable = 0
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return repr
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def _safe_repr(object, context, maxlevels=None, level=0):
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level = level + 1
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readable = 1
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typ = type(object)
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if not (typ in (DictType, ListType, TupleType) and object):
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rep = `object`
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if rep:
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if rep[0] == '<':
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readable = 0
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else:
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readable = 0
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return `object`, readable
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if context.has_key(id(object)):
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return `_Recursion(object)`, 0
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objid = id(object)
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context[objid] = 1
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if typ is DictType:
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if maxlevels and level >= maxlevels:
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s = "{...}"
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readable = 0
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else:
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items = object.items()
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k, v = items[0]
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krepr, kreadable = _safe_repr(k, context, maxlevels, level)
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vrepr, vreadable = _safe_repr(v, context, maxlevels, level)
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readable = readable and kreadable and vreadable
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s = "{%s: %s" % (krepr, vrepr)
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for k, v in items[1:]:
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krepr, kreadable = _safe_repr(k, context, maxlevels, level)
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vrepr, vreadable = _safe_repr(v, context, maxlevels, level)
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readable = readable and kreadable and vreadable
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s = "%s, %s: %s" % (s, krepr, vrepr)
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s = s + "}"
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else:
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s, term = (typ is ListType) and ('[', ']') or ('(', ')')
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if maxlevels and level >= maxlevels:
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s = s + "..."
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readable = 0
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else:
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subrepr, subreadable = _safe_repr(
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object[0], context, maxlevels, level)
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readable = readable and subreadable
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s = s + subrepr
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tail = object[1:]
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if not tail:
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if typ is TupleType:
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s = s + ','
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for ent in tail:
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subrepr, subreadable = _safe_repr(
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ent, context, maxlevels, level)
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readable = readable and subreadable
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s = "%s, %s" % (s, subrepr)
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s = s + term
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del context[objid]
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return s, readable
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class _Recursion:
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# represent a recursive relationship; really only used for the __repr__()
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# method...
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def __init__(self, object):
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self.__repr = "<Recursion on %s with id=%s>" \
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% (type(object).__name__, id(object))
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def __repr__(self):
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return self.__repr
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