# 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.time()
_safe_repr(object, {}, None, 0)
t2 = time.time()
p.pformat(object)
t3 = time.time()
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()
