# Author: Fred L. Drake, Jr. # fdrake@cnri.reston.va.us, 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.sydout]. saferepr() Generate a 'standard' repr()-like value, but protect against recursive data structures. """ from types import DictType, ListType, TupleType try: from cStringIO import StringIO except ImportError: from StringIO import StringIO __all__ = ["pprint","pformat","isreadable","isrecursive","saferepr", "PrettyPrinter"] def pprint(object, stream=None): """Pretty-print a Python object to a stream [default is sys.sydout].""" printer = PrettyPrinter(stream=stream) printer.pprint(object) def pformat(object): """Format a Python object into a pretty-printed representation.""" return PrettyPrinter().pformat(object) def saferepr(object): """Version of repr() which can handle recursive data structures.""" return _safe_repr(object, {})[0] def isreadable(object): """Determine if saferepr(object) is readable by eval().""" return _safe_repr(object, {})[1] def isrecursive(object): """Determine if object requires a recursive representation.""" return _safe_repr(object, {})[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 assert depth is None or depth > 0, "depth must be > 0" assert width self.__depth = depth self.__indent_per_level = indent self.__width = width if stream: self.__stream = stream else: import sys self.__stream = sys.stdout def pprint(self, object): self.__stream.write(self.pformat(object) + "\n") def pformat(self, object): sio = StringIO() self.__format(object, sio, 0, 0, {}, 0) return sio.getvalue() def isrecursive(self, object): self.__recursive = 0 self.pformat(object) return self.__recursive def isreadable(self, object): self.__recursive = 0 self.__readable = 1 self.pformat(object) return self.__readable and not self.__recursive def __format(self, object, stream, indent, allowance, context, level): level = level + 1 if context.has_key(id(object)): object = _Recursion(object) self.__recursive = 1 rep = self.__repr(object, context, level - 1) objid = id(object) context[objid] = 1 typ = type(object) sepLines = len(rep) > (self.__width - 1 - indent - allowance) if sepLines and typ in (ListType, TupleType): # Pretty-print the sequence. stream.write((typ is ListType) and '[' or '(') if self.__indent_per_level > 1: stream.write((self.__indent_per_level - 1) * ' ') length = len(object) if length: indent = indent + self.__indent_per_level self.__format(object[0], stream, indent, allowance + 1, context, level) if length > 1: for ent in object[1:]: stream.write(',\n' + ' '*indent) self.__format(ent, stream, indent, allowance + 1, context, level) indent = indent - self.__indent_per_level if typ is TupleType and length == 1: stream.write(',') stream.write(((typ is ListType) and ']') or ')') elif sepLines and typ is DictType: stream.write('{') if self.__indent_per_level > 1: stream.write((self.__indent_per_level - 1) * ' ') length = len(object) if length: indent = indent + self.__indent_per_level items = object.items() items.sort() key, ent = items[0] rep = self.__repr(key, context, level) + ': ' stream.write(rep) self.__format(ent, stream, indent + len(rep), allowance + 1, context, level) if len(items) > 1: for key, ent in items[1:]: rep = self.__repr(key, context, level) + ': ' stream.write(',\n' + ' '*indent + rep) self.__format(ent, stream, indent + len(rep), allowance + 1, context, level) indent = indent - self.__indent_per_level stream.write('}') else: stream.write(rep) del context[objid] def __repr(self, object, context, level): repr, readable, recursive = _safe_repr(object, context, self.__depth, level) if not readable: self.__readable = 0 if recursive: self.__recursive = 1 return repr # Return triple (repr_string, isreadable, isrecursive). def _safe_repr(object, context, maxlevels=None, level=0): level = level + 1 typ = type(object) if not (typ in (DictType, ListType, TupleType) and object): rep = `object` return rep, (rep and (rep[0] != '<')), 0 if context.has_key(id(object)): return `_Recursion(object)`, 0, 1 objid = id(object) context[objid] = 1 readable = 1 recursive = 0 if typ is DictType: if maxlevels and level >= maxlevels: s = "{...}" readable = 0 else: items = object.items() k, v = items[0] krepr, kreadable, krecur = _safe_repr(k, context, maxlevels, level) vrepr, vreadable, vrecur = _safe_repr(v, context, maxlevels, level) readable = readable and kreadable and vreadable recursive = recursive or krecur or vrecur s = "{%s: %s" % (krepr, vrepr) for k, v in items[1:]: krepr, kreadable, krecur = _safe_repr(k, context, maxlevels, level) vrepr, vreadable, vrecur = _safe_repr(v, context, maxlevels, level) readable = readable and kreadable and vreadable recursive = recursive or krecur or vrecur s = "%s, %s: %s" % (s, krepr, vrepr) s = s + "}" else: s, term = (typ is ListType) and ('[', ']') or ('(', ')') if maxlevels and level >= maxlevels: s = s + "..." readable = 0 else: subrepr, subreadable, subrecur = _safe_repr( object[0], context, maxlevels, level) readable = readable and subreadable recursive = recursive or subrecur s = s + subrepr tail = object[1:] if not tail: if typ is TupleType: s = s + ',' for ent in tail: subrepr, subreadable, subrecur = _safe_repr( ent, context, maxlevels, level) readable = readable and subreadable recursive = recursive or subrecur s = "%s, %s" % (s, subrepr) s = s + term del context[objid] return s, readable and not recursive, recursive class _Recursion: # represent a recursive relationship; really only used for the __repr__() # method... def __init__(self, object): self.__repr = "" \ % (type(object).__name__, id(object)) def __repr__(self): return self.__repr