# 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 sys as _sys

import types as _types

from io import StringIO as _StringIO

__all__ = ["pprint","pformat","isreadable","isrecursive","saferepr",

"PrettyPrinter", "pp"]

def pprint(object, stream=None, indent=1, width=80, depth=None, *,

compact=False, sort_dicts=True, underscore_numbers=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, sort_dicts=sort_dicts,

underscore_numbers=underscore_numbers)

printer.pprint(object)

def pformat(object, indent=1, width=80, depth=None, *,

compact=False, sort_dicts=True, underscore_numbers=False):

"""Format a Python object into a pretty-printed representation."""

return PrettyPrinter(indent=indent, width=width, depth=depth,

compact=compact, sort_dicts=sort_dicts,

underscore_numbers=underscore_numbers).pformat(object)

def pp(object, *args, sort_dicts=False, **kwargs):

"""Pretty-print a Python object"""

pprint(object, *args, sort_dicts=sort_dicts, **kwargs)

def saferepr(object):

"""Version of repr() which can handle recursive data structures."""

return PrettyPrinter()._safe_repr(object, {}, None, 0)[0]

def isreadable(object):

"""Determine if saferepr(object) is readable by eval()."""

return PrettyPrinter()._safe_repr(object, {}, None, 0)[1]

def isrecursive(object):

"""Determine if object requires a recursive representation."""

return PrettyPrinter()._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, sort_dicts=True, underscore_numbers=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.

sort_dicts

If true, dict keys are sorted.

underscore_numbers

If true, digit groups are separated with underscores.

"""

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)

self._sort_dicts = sort_dicts

self._underscore_numbers = underscore_numbers

def pprint(self, object):

if self._stream is not None:

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)

# Lazy import to improve module import time

from dataclasses import is_dataclass

if p is not None:

context[objid] = 1

p(self, object, stream, indent, allowance, context, level + 1)

del context[objid]

return

elif (is_dataclass(object) and

not isinstance(object, type) and

object.__dataclass_params__.repr and

# Check dataclass has generated repr method.

hasattr(object.__repr__, "__wrapped__") and

"__create_fn__" in object.__repr__.__wrapped__.__qualname__):

context[objid] = 1

self._pprint_dataclass(object, stream, indent, allowance, context, level + 1)

del context[objid]

return

stream.write(rep)

def _pprint_dataclass(self, object, stream, indent, allowance, context, level):

# Lazy import to improve module import time

from dataclasses import fields as dataclass_fields

cls_name = object.__class__.__name__

indent += len(cls_name) + 1

items = [(f.name, getattr(object, f.name)) for f in dataclass_fields(object) if f.repr]

stream.write(cls_name + '(')

self._format_namespace_items(items, stream, indent, allowance, context, level)

stream.write(')')

_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:

if self._sort_dicts:

items = sorted(object.items(), key=_safe_tuple)

else:

items = object.items()

self._format_dict_items(items, stream, indent, allowance + 1,

context, level)

write('}')

_dispatch[dict.__repr__] = _pprint_dict

def _pprint_frozendict(self, object, stream, indent, allowance, context, level):

write = stream.write

cls = object.__class__

write(cls.__name__ + '(')

length = len(object)

if length:

self._pprint_dict(object, stream,

indent + len(cls.__name__) + 1,

allowance + 1,

context, level)

write(')')

_dispatch[frozendict.__repr__] = _pprint_frozendict

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_dict_view(self, object, stream, indent, allowance, context, level):

"""Pretty print dict views (keys, values, items)."""

if isinstance(object, self._dict_items_view):

key = _safe_tuple

else:

key = _safe_key

write = stream.write

write(object.__class__.__name__ + '([')

if self._indent_per_level > 1:

write((self._indent_per_level - 1) * ' ')

length = len(object)

if length:

if self._sort_dicts:

entries = sorted(object, key=key)

else:

entries = object

self._format_items(entries, stream, indent, allowance + 1,

context, level)

write('])')

def _pprint_mapping_abc_view(self, object, stream, indent, allowance, context, level):

"""Pretty print mapping views from collections.abc."""

write = stream.write

write(object.__class__.__name__ + '(')

# Dispatch formatting to the view's _mapping

self._format(object._mapping, stream, indent, allowance, context, level)

write(')')

_dict_keys_view = type({}.keys())

_dispatch[_dict_keys_view.__repr__] = _pprint_dict_view

_dict_values_view = type({}.values())

_dispatch[_dict_values_view.__repr__] = _pprint_dict_view

_dict_items_view = type({}.items())

_dispatch[_dict_items_view.__repr__] = _pprint_dict_view

_dispatch[_collections.abc.MappingView.__repr__] = _pprint_mapping_abc_view

_view_reprs = {cls.__repr__ for cls in

(_dict_keys_view, _dict_values_view, _dict_items_view,

_collections.abc.MappingView)}

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:

# Lazy import to improve module import time

import re

# 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 _pprint_simplenamespace(self, object, stream, indent, allowance, context, level):

if type(object) is _types.SimpleNamespace:

# The SimpleNamespace repr is "namespace" instead of the class

# name, so we do the same here. For subclasses; use the class name.

cls_name = 'namespace'

else:

cls_name = object.__class__.__name__

indent += len(cls_name) + 1

items = object.__dict__.items()

stream.write(cls_name + '(')

self._format_namespace_items(items, stream, indent, allowance, context, level)

stream.write(')')

_dispatch[_types.SimpleNamespace.__repr__] = _pprint_simplenamespace

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_namespace_items(self, items, stream, indent, allowance, context, level):

write = stream.write

delimnl = ',\n' + ' ' * indent

last_index = len(items) - 1

for i, (key, ent) in enumerate(items):

last = i == last_index

write(key)

write('=')

if id(ent) in context:

# Special-case representation of recursion to match standard

# recursive dataclass repr.

write("...")

else:

self._format(ent, stream, indent + len(key) + 1,

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 self._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

def _safe_repr(self, object, context, maxlevels, level):

# Return triple (repr_string, isreadable, isrecursive).

typ = type(object)

if typ in _builtin_scalars:

return repr(object), True, False

r = getattr(typ, "__repr__", None)

if issubclass(typ, int) and r is int.__repr__:

if self._underscore_numbers:

return f"{object:_d}", True, False

else:

return repr(object), True, False

if ((issubclass(typ, dict) and r is dict.__repr__)

or (issubclass(typ, frozendict) and r is frozendict.__repr__)):

is_frozendict = issubclass(typ, frozendict)

if not object:

if is_frozendict:

rep = f"{object.__class__.__name__}()"

else:

rep = "{}"

return rep, True, False

objid = id(object)

if maxlevels and level >= maxlevels:

rep = "{...}"

if is_frozendict:

rep = f"{object.__class__.__name__}({rep})"

return rep, 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

if self._sort_dicts:

items = sorted(object.items(), key=_safe_tuple)

else:

items = object.items()

for k, v in items:

krepr, kreadable, krecur = self.format(

k, context, maxlevels, level)

vrepr, vreadable, vrecur = self.format(

v, context, maxlevels, level)

append("%s: %s" % (krepr, vrepr))

readable = readable and kreadable and vreadable

if krecur or vrecur:

recursive = True

del context[objid]

rep = "{%s}" % ", ".join(components)

if is_frozendict:

rep = f"{object.__class__.__name__}({rep})"

return rep, 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 = self.format(

o, context, maxlevels, level)

append(orepr)

if not oreadable:

readable = False

if orecur:

recursive = True

del context[objid]

return format % ", ".join(components), readable, recursive

if issubclass(typ, _collections.abc.MappingView) and r in self._view_reprs:

objid = id(object)

if maxlevels and level >= maxlevels:

return "{...}", False, objid in context

if objid in context:

return _recursion(object), False, True

key = _safe_key

if issubclass(typ, (self._dict_items_view, _collections.abc.ItemsView)):

key = _safe_tuple

if hasattr(object, "_mapping"):

# Dispatch formatting to the view's _mapping

mapping_repr, readable, recursive = self.format(

object._mapping, context, maxlevels, level)

return (typ.__name__ + '(%s)' % mapping_repr), readable, recursive

elif hasattr(typ, "_mapping"):

# We have a view that somehow has lost its type's _mapping, raise

# an error by calling repr() instead of failing cryptically later

return repr(object), True, False

if self._sort_dicts:

object = sorted(object, key=key)

context[objid] = 1

readable = True

recursive = False

components = []

append = components.append

level += 1

for val in object:

vrepr, vreadable, vrecur = self.format(

val, context, maxlevels, level)

append(vrepr)

readable = readable and vreadable

if vrecur:

recursive = True

del context[objid]

return typ.__name__ + '([%s])' % ", ".join(components), readable, recursive

rep = repr(object)

return rep, (rep and not rep.startswith('<')), False

_builtin_scalars = frozenset({str, bytes, bytearray, float, complex,

bool, type(None)})

def _recursion(object):

return ("<Recursion on %s with id=%s>"

% (type(object).__name__, id(object)))

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)