# 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 collections as _collections import re import sys as _sys import types as _types from io import StringIO as _StringIO __all__ = ["pprint","pformat","isreadable","isrecursive","saferepr", "PrettyPrinter"] def pprint(object, stream=None, indent=1, width=80, depth=None, *, compact=False): """Pretty-print a Python object to a stream [default is sys.stdout].""" printer = PrettyPrinter( stream=stream, indent=indent, width=width, depth=depth, compact=compact) printer.pprint(object) def pformat(object, indent=1, width=80, depth=None, *, compact=False): """Format a Python object into a pretty-printed representation.""" return PrettyPrinter(indent=indent, width=width, depth=depth, compact=compact).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 _safe_key: """Helper function for key functions when sorting unorderable objects. The wrapped-object will fallback to a Py2.x style comparison for unorderable types (sorting first comparing the type name and then by the obj ids). Does not work recursively, so dict.items() must have _safe_key applied to both the key and the value. """ __slots__ = ['obj'] def __init__(self, obj): self.obj = obj def __lt__(self, other): try: return self.obj < other.obj except TypeError: return ((str(type(self.obj)), id(self.obj)) < \ (str(type(other.obj)), id(other.obj))) def _safe_tuple(t): "Helper function for comparing 2-tuples" return _safe_key(t[0]), _safe_key(t[1]) class PrettyPrinter: def __init__(self, indent=1, width=80, depth=None, stream=None, *, compact=False): """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. compact If true, several items will be combined in one line. """ indent = int(indent) width = int(width) if indent < 0: raise ValueError('indent must be >= 0') if depth is not None and depth <= 0: raise ValueError('depth must be > 0') if not width: raise ValueError('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 self._compact = bool(compact) 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): objid = id(object) if objid in context: stream.write(_recursion(object)) self._recursive = True self._readable = False return rep = self._repr(object, context, level) max_width = self._width - indent - allowance if len(rep) > max_width: p = self._dispatch.get(type(object).__repr__, None) if p is not None: context[objid] = 1 p(self, object, stream, indent, allowance, context, level + 1) del context[objid] return elif isinstance(object, dict): context[objid] = 1 self._pprint_dict(object, stream, indent, allowance, context, level + 1) del context[objid] return stream.write(rep) _dispatch = {} def _pprint_dict(self, object, stream, indent, allowance, context, level): write = stream.write write('{') if self._indent_per_level > 1: write((self._indent_per_level - 1) * ' ') length = len(object) if length: items = sorted(object.items(), key=_safe_tuple) self._format_dict_items(items, stream, indent, allowance + 1, context, level) write('}') _dispatch[dict.__repr__] = _pprint_dict def _pprint_ordered_dict(self, object, stream, indent, allowance, context, level): if not len(object): stream.write(repr(object)) return cls = object.__class__ stream.write(cls.__name__ + '(') self._format(list(object.items()), stream, indent + len(cls.__name__) + 1, allowance + 1, context, level) stream.write(')') _dispatch[_collections.OrderedDict.__repr__] = _pprint_ordered_dict def _pprint_list(self, object, stream, indent, allowance, context, level): stream.write('[') self._format_items(object, stream, indent, allowance + 1, context, level) stream.write(']') _dispatch[list.__repr__] = _pprint_list def _pprint_tuple(self, object, stream, indent, allowance, context, level): stream.write('(') endchar = ',)' if len(object) == 1 else ')' self._format_items(object, stream, indent, allowance + len(endchar), context, level) stream.write(endchar) _dispatch[tuple.__repr__] = _pprint_tuple def _pprint_set(self, object, stream, indent, allowance, context, level): if not len(object): stream.write(repr(object)) return typ = object.__class__ if typ is set: stream.write('{') endchar = '}' else: stream.write(typ.__name__ + '({') endchar = '})' indent += len(typ.__name__) + 1 object = sorted(object, key=_safe_key) self._format_items(object, stream, indent, allowance + len(endchar), context, level) stream.write(endchar) _dispatch[set.__repr__] = _pprint_set _dispatch[frozenset.__repr__] = _pprint_set def _pprint_str(self, object, stream, indent, allowance, context, level): write = stream.write if not len(object): write(repr(object)) return chunks = [] lines = object.splitlines(True) if level == 1: indent += 1 allowance += 1 max_width1 = max_width = self._width - indent for i, line in enumerate(lines): rep = repr(line) if i == len(lines) - 1: max_width1 -= allowance if len(rep) <= max_width1: chunks.append(rep) else: # A list of alternating (non-space, space) strings parts = re.findall(r'\S*\s*', line) assert parts assert not parts[-1] parts.pop() # drop empty last part max_width2 = max_width current = '' for j, part in enumerate(parts): candidate = current + part if j == len(parts) - 1 and i == len(lines) - 1: max_width2 -= allowance if len(repr(candidate)) > max_width2: if current: chunks.append(repr(current)) current = part else: current = candidate if current: chunks.append(repr(current)) if len(chunks) == 1: write(rep) return if level == 1: write('(') for i, rep in enumerate(chunks): if i > 0: write('\n' + ' '*indent) write(rep) if level == 1: write(')') _dispatch[str.__repr__] = _pprint_str def _pprint_bytes(self, object, stream, indent, allowance, context, level): write = stream.write if len(object) <= 4: write(repr(object)) return parens = level == 1 if parens: indent += 1 allowance += 1 write('(') delim = '' for rep in _wrap_bytes_repr(object, self._width - indent, allowance): write(delim) write(rep) if not delim: delim = '\n' + ' '*indent if parens: write(')') _dispatch[bytes.__repr__] = _pprint_bytes def _pprint_bytearray(self, object, stream, indent, allowance, context, level): write = stream.write write('bytearray(') self._pprint_bytes(bytes(object), stream, indent + 10, allowance + 1, context, level + 1) write(')') _dispatch[bytearray.__repr__] = _pprint_bytearray def _pprint_mappingproxy(self, object, stream, indent, allowance, context, level): stream.write('mappingproxy(') self._format(object.copy(), stream, indent + 13, allowance + 1, context, level) stream.write(')') _dispatch[_types.MappingProxyType.__repr__] = _pprint_mappingproxy def _format_dict_items(self, items, stream, indent, allowance, context, level): write = stream.write indent += self._indent_per_level delimnl = ',\n' + ' ' * indent last_index = len(items) - 1 for i, (key, ent) in enumerate(items): last = i == last_index rep = self._repr(key, context, level) write(rep) write(': ') self._format(ent, stream, indent + len(rep) + 2, allowance if last else 1, context, level) if not last: write(delimnl) def _format_items(self, items, stream, indent, allowance, context, level): write = stream.write indent += self._indent_per_level if self._indent_per_level > 1: write((self._indent_per_level - 1) * ' ') delimnl = ',\n' + ' ' * indent delim = '' width = max_width = self._width - indent + 1 it = iter(items) try: next_ent = next(it) except StopIteration: return last = False while not last: ent = next_ent try: next_ent = next(it) except StopIteration: last = True max_width -= allowance width -= allowance if self._compact: rep = self._repr(ent, context, level) w = len(rep) + 2 if width < w: width = max_width if delim: delim = delimnl if width >= w: width -= w write(delim) delim = ', ' write(rep) continue write(delim) delim = delimnl self._format(ent, stream, indent, allowance if last else 1, context, level) 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) def _pprint_default_dict(self, object, stream, indent, allowance, context, level): if not len(object): stream.write(repr(object)) return rdf = self._repr(object.default_factory, context, level) cls = object.__class__ indent += len(cls.__name__) + 1 stream.write('%s(%s,\n%s' % (cls.__name__, rdf, ' ' * indent)) self._pprint_dict(object, stream, indent, allowance + 1, context, level) stream.write(')') _dispatch[_collections.defaultdict.__repr__] = _pprint_default_dict def _pprint_counter(self, object, stream, indent, allowance, context, level): if not len(object): stream.write(repr(object)) return cls = object.__class__ stream.write(cls.__name__ + '({') if self._indent_per_level > 1: stream.write((self._indent_per_level - 1) * ' ') items = object.most_common() self._format_dict_items(items, stream, indent + len(cls.__name__) + 1, allowance + 2, context, level) stream.write('})') _dispatch[_collections.Counter.__repr__] = _pprint_counter def _pprint_chain_map(self, object, stream, indent, allowance, context, level): if not len(object.maps): stream.write(repr(object)) return cls = object.__class__ stream.write(cls.__name__ + '(') indent += len(cls.__name__) + 1 for i, m in enumerate(object.maps): if i == len(object.maps) - 1: self._format(m, stream, indent, allowance + 1, context, level) stream.write(')') else: self._format(m, stream, indent, 1, context, level) stream.write(',\n' + ' ' * indent) _dispatch[_collections.ChainMap.__repr__] = _pprint_chain_map def _pprint_deque(self, object, stream, indent, allowance, context, level): if not len(object): stream.write(repr(object)) return cls = object.__class__ stream.write(cls.__name__ + '(') indent += len(cls.__name__) + 1 stream.write('[') if object.maxlen is None: self._format_items(object, stream, indent, allowance + 2, context, level) stream.write('])') else: self._format_items(object, stream, indent, 2, context, level) rml = self._repr(object.maxlen, context, level) stream.write('],\n%smaxlen=%s)' % (' ' * indent, rml)) _dispatch[_collections.deque.__repr__] = _pprint_deque def _pprint_user_dict(self, object, stream, indent, allowance, context, level): self._format(object.data, stream, indent, allowance, context, level - 1) _dispatch[_collections.UserDict.__repr__] = _pprint_user_dict def _pprint_user_list(self, object, stream, indent, allowance, context, level): self._format(object.data, stream, indent, allowance, context, level - 1) _dispatch[_collections.UserList.__repr__] = _pprint_user_list def _pprint_user_string(self, object, stream, indent, allowance, context, level): self._format(object.data, stream, indent, allowance, context, level - 1) _dispatch[_collections.UserString.__repr__] = _pprint_user_string # Return triple (repr_string, isreadable, isrecursive). def _safe_repr(object, context, maxlevels, level): typ = type(object) if typ in _builtin_scalars: return repr(object), 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 items = sorted(object.items(), key=_safe_tuple) for k, v in 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}" % ", ".join(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 % ", ".join(components), readable, recursive rep = repr(object) return rep, (rep and not rep.startswith('<')), False _builtin_scalars = frozenset({str, bytes, bytearray, int, float, complex, bool, type(None)}) 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.perf_counter() _safe_repr(object, {}, None, 0) t2 = time.perf_counter() p.pformat(object) t3 = time.perf_counter() print("_safe_repr:", t2 - t1) print("pformat:", t3 - t2) def _wrap_bytes_repr(object, width, allowance): current = b'' last = len(object) // 4 * 4 for i in range(0, len(object), 4): part = object[i: i+4] candidate = current + part if i == last: width -= allowance if len(repr(candidate)) > width: if current: yield repr(current) current = part else: current = candidate if current: yield repr(current) if __name__ == "__main__": _perfcheck()