cpython/Lib/pprint.py at a7da1663ecf9a881970b096a6dd0494584d0f795 · python/cpython · GitHub

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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 sys as _sys

from io import StringIO as _StringIO

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

"PrettyPrinter"]

# cache these for faster access:

_commajoin = ", ".join

_id = id

_len = len

_type = type

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

"""Pretty-print a Python object to a stream [default is sys.stdout]."""

printer = PrettyPrinter(

stream=stream, indent=indent, width=width, depth=depth)

printer.pprint(object)

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

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

return PrettyPrinter(indent=indent, width=width, depth=depth).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):

rv = self.obj.__lt__(other.obj)

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):

"""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, "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

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)

sepLines = _len(rep) > (self._width - 1 - indent - allowance)

write = stream.write

if self._depth and level > self._depth:

write(rep)

return

if sepLines:

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

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

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

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, set):

if not length:

write('set()')

return

write('{')

endchar = '}'

object = sorted(object, key=_safe_key)

elif issubclass(typ, frozenset):

if not length:

write('frozenset()')

return

write('frozenset({')

endchar = '})'

object = sorted(object, key=_safe_key)

indent += 10

else:

write('(')

endchar = ')'

if self._indent_per_level > 1:

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

if length:

context[objid] = 1

indent = indent + self._indent_per_level

self._format(object[0], stream, indent, allowance + 1,

context, level)

if length > 1:

for ent in object[1:]:

write(',\n' + ' '*indent)

self._format(ent, stream, indent,

allowance + 1, context, level)

indent = indent - self._indent_per_level

del context[objid]

if issubclass(typ, tuple) and length == 1:

write(',')

write(endchar)

return

write(rep)

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}" % _commajoin(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 % _commajoin(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()

cpython/Lib/pprint.py at a7da1663ecf9a881970b096a6dd0494584d0f795 · python/cpython · GitHub

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