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pprint.py
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# 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 re import sys as _sys from collections import OrderedDict as _OrderedDict 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 an 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: rv = self.obj.__lt__(other.obj) except TypeError: rv = NotImplemented if rv is NotImplemented: rv = (str(type(self.obj)), id(self.obj)) < \ (str(type(other.obj)), id(other.obj)) return rv 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) 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 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): 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) max_width = self._width - 1 - indent - allowance sepLines = len(rep) > max_width write = stream.write if sepLines: r = getattr(typ, "__repr__", None) if issubclass(typ, dict): 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 if issubclass(typ, _OrderedDict): items = list(object.items()) else: items = sorted(object.items(), key=_safe_tuple) 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__) 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, tuple): write('(') endchar = ')' else: if not length: write(rep) return if typ is set: write('{') endchar = '}' else: write(typ.__name__) write('({') endchar = '})' indent += len(typ.__name__) + 1 object = sorted(object, key=_safe_key) if self._indent_per_level > 1: write((self._indent_per_level - 1) * ' ') if length: context[objid] = 1 self._format_items(object, stream, indent + self._indent_per_level, allowance + 1, context, level) del context[objid] if issubclass(typ, tuple) and length == 1: write(',') write(endchar) return if issubclass(typ, str) and len(object) > 0 and r is str.__repr__: chunks = [] lines = object.splitlines(True) if level == 1: indent += 1 max_width -= 2 for i, line in enumerate(lines): rep = repr(line) if len(rep) <= max_width: chunks.append(rep) else: # A list of alternating (non-space, space) strings parts = re.split(r'(\s+)', line) + [''] current = '' for i in range(0, len(parts), 2): part = parts[i] + parts[i+1] candidate = current + part if len(repr(candidate)) > max_width: 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(')') return write(rep) def _format_items(self, items, stream, indent, allowance, context, level): write = stream.write delimnl = ',\n' + ' ' * indent delim = '' width = max_width = self._width - indent - allowance + 2 for ent in items: 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, 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) # 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 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 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()