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468 lines
15 KiB
Python
468 lines
15 KiB
Python
# Author: Fred L. Drake, Jr.
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# fdrake@acm.org
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#
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# This is a simple little module I wrote to make life easier. I didn't
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# see anything quite like it in the library, though I may have overlooked
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# something. I wrote this when I was trying to read some heavily nested
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# tuples with fairly non-descriptive content. This is modeled very much
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# after Lisp/Scheme - style pretty-printing of lists. If you find it
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# useful, thank small children who sleep at night.
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"""Support to pretty-print lists, tuples, & dictionaries recursively.
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Very simple, but useful, especially in debugging data structures.
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Classes
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-------
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PrettyPrinter()
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Handle pretty-printing operations onto a stream using a configured
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set of formatting parameters.
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Functions
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---------
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pformat()
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Format a Python object into a pretty-printed representation.
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pprint()
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Pretty-print a Python object to a stream [default is sys.stdout].
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saferepr()
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Generate a 'standard' repr()-like value, but protect against recursive
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data structures.
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"""
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import re
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import sys as _sys
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from collections import OrderedDict as _OrderedDict
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from io import StringIO as _StringIO
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__all__ = ["pprint","pformat","isreadable","isrecursive","saferepr",
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"PrettyPrinter"]
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def pprint(object, stream=None, indent=1, width=80, depth=None, *,
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compact=False):
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"""Pretty-print a Python object to a stream [default is sys.stdout]."""
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printer = PrettyPrinter(
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stream=stream, indent=indent, width=width, depth=depth,
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compact=compact)
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printer.pprint(object)
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def pformat(object, indent=1, width=80, depth=None, *, compact=False):
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"""Format a Python object into a pretty-printed representation."""
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return PrettyPrinter(indent=indent, width=width, depth=depth,
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compact=compact).pformat(object)
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def saferepr(object):
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"""Version of repr() which can handle recursive data structures."""
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return _safe_repr(object, {}, None, 0)[0]
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def isreadable(object):
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"""Determine if saferepr(object) is readable by eval()."""
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return _safe_repr(object, {}, None, 0)[1]
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def isrecursive(object):
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"""Determine if object requires a recursive representation."""
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return _safe_repr(object, {}, None, 0)[2]
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class _safe_key:
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"""Helper function for key functions when sorting unorderable objects.
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The wrapped-object will fallback to an Py2.x style comparison for
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unorderable types (sorting first comparing the type name and then by
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the obj ids). Does not work recursively, so dict.items() must have
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_safe_key applied to both the key and the value.
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"""
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__slots__ = ['obj']
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def __init__(self, obj):
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self.obj = obj
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def __lt__(self, other):
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try:
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rv = self.obj.__lt__(other.obj)
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except TypeError:
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rv = NotImplemented
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if rv is NotImplemented:
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rv = (str(type(self.obj)), id(self.obj)) < \
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(str(type(other.obj)), id(other.obj))
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return rv
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def _safe_tuple(t):
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"Helper function for comparing 2-tuples"
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return _safe_key(t[0]), _safe_key(t[1])
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class PrettyPrinter:
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def __init__(self, indent=1, width=80, depth=None, stream=None, *,
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compact=False):
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"""Handle pretty printing operations onto a stream using a set of
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configured parameters.
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indent
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Number of spaces to indent for each level of nesting.
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width
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Attempted maximum number of columns in the output.
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depth
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The maximum depth to print out nested structures.
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stream
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The desired output stream. If omitted (or false), the standard
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output stream available at construction will be used.
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compact
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If true, several items will be combined in one line.
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"""
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indent = int(indent)
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width = int(width)
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assert indent >= 0, "indent must be >= 0"
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assert depth is None or depth > 0, "depth must be > 0"
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assert width, "width must be != 0"
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self._depth = depth
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self._indent_per_level = indent
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self._width = width
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if stream is not None:
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self._stream = stream
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else:
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self._stream = _sys.stdout
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self._compact = bool(compact)
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def pprint(self, object):
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self._format(object, self._stream, 0, 0, {}, 0)
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self._stream.write("\n")
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def pformat(self, object):
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sio = _StringIO()
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self._format(object, sio, 0, 0, {}, 0)
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return sio.getvalue()
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def isrecursive(self, object):
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return self.format(object, {}, 0, 0)[2]
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def isreadable(self, object):
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s, readable, recursive = self.format(object, {}, 0, 0)
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return readable and not recursive
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def _format(self, object, stream, indent, allowance, context, level):
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objid = id(object)
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if objid in context:
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stream.write(_recursion(object))
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self._recursive = True
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self._readable = False
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return
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rep = self._repr(object, context, level)
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max_width = self._width - indent - allowance
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if len(rep) > max_width:
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p = self._dispatch.get(type(object).__repr__, None)
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if p is not None:
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context[objid] = 1
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p(self, object, stream, indent, allowance, context, level + 1)
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del context[objid]
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return
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elif isinstance(object, dict):
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context[objid] = 1
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self._pprint_dict(object, stream, indent, allowance,
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context, level + 1)
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del context[objid]
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return
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stream.write(rep)
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_dispatch = {}
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def _pprint_dict(self, object, stream, indent, allowance, context, level):
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write = stream.write
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write('{')
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if self._indent_per_level > 1:
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write((self._indent_per_level - 1) * ' ')
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length = len(object)
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if length:
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if isinstance(object, _OrderedDict):
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items = list(object.items())
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else:
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items = sorted(object.items(), key=_safe_tuple)
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self._format_dict_items(items, stream, indent, allowance + 1,
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context, level)
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write('}')
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_dispatch[dict.__repr__] = _pprint_dict
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_dispatch[_OrderedDict.__repr__] = _pprint_dict
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def _pprint_list(self, object, stream, indent, allowance, context, level):
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stream.write('[')
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self._format_items(object, stream, indent, allowance + 1,
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context, level)
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stream.write(']')
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_dispatch[list.__repr__] = _pprint_list
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def _pprint_tuple(self, object, stream, indent, allowance, context, level):
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stream.write('(')
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endchar = ',)' if len(object) == 1 else ')'
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self._format_items(object, stream, indent, allowance + len(endchar),
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context, level)
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stream.write(endchar)
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_dispatch[tuple.__repr__] = _pprint_tuple
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def _pprint_set(self, object, stream, indent, allowance, context, level):
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if not len(object):
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stream.write(repr(object))
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return
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typ = object.__class__
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if typ is set:
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stream.write('{')
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endchar = '}'
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else:
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stream.write(typ.__name__ + '({')
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endchar = '})'
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indent += len(typ.__name__) + 1
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object = sorted(object, key=_safe_key)
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self._format_items(object, stream, indent, allowance + len(endchar),
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context, level)
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stream.write(endchar)
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_dispatch[set.__repr__] = _pprint_set
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_dispatch[frozenset.__repr__] = _pprint_set
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def _pprint_str(self, object, stream, indent, allowance, context, level):
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write = stream.write
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if not len(object):
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write(repr(object))
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return
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chunks = []
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lines = object.splitlines(True)
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if level == 1:
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indent += 1
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allowance += 1
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max_width1 = max_width = self._width - indent
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for i, line in enumerate(lines):
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rep = repr(line)
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if i == len(lines) - 1:
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max_width1 -= allowance
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if len(rep) <= max_width1:
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chunks.append(rep)
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else:
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# A list of alternating (non-space, space) strings
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parts = re.findall(r'\S*\s*', line)
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assert parts
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assert not parts[-1]
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parts.pop() # drop empty last part
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max_width2 = max_width
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current = ''
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for j, part in enumerate(parts):
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candidate = current + part
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if j == len(parts) - 1 and i == len(lines) - 1:
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max_width2 -= allowance
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if len(repr(candidate)) > max_width2:
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if current:
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chunks.append(repr(current))
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current = part
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else:
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current = candidate
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if current:
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chunks.append(repr(current))
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if len(chunks) == 1:
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write(rep)
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return
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if level == 1:
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write('(')
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for i, rep in enumerate(chunks):
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if i > 0:
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write('\n' + ' '*indent)
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write(rep)
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if level == 1:
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write(')')
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_dispatch[str.__repr__] = _pprint_str
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def _format_dict_items(self, items, stream, indent, allowance, context,
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level):
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write = stream.write
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indent += self._indent_per_level
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delimnl = ',\n' + ' ' * indent
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last_index = len(items) - 1
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for i, (key, ent) in enumerate(items):
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last = i == last_index
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rep = self._repr(key, context, level)
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write(rep)
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write(': ')
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self._format(ent, stream, indent + len(rep) + 2,
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allowance if last else 1,
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context, level)
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if not last:
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write(delimnl)
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def _format_items(self, items, stream, indent, allowance, context, level):
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write = stream.write
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indent += self._indent_per_level
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if self._indent_per_level > 1:
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write((self._indent_per_level - 1) * ' ')
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delimnl = ',\n' + ' ' * indent
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delim = ''
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width = max_width = self._width - indent + 1
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it = iter(items)
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try:
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next_ent = next(it)
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except StopIteration:
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return
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last = False
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while not last:
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ent = next_ent
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try:
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next_ent = next(it)
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except StopIteration:
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last = True
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max_width -= allowance
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width -= allowance
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if self._compact:
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rep = self._repr(ent, context, level)
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w = len(rep) + 2
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if width < w:
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width = max_width
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if delim:
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delim = delimnl
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if width >= w:
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width -= w
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write(delim)
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delim = ', '
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write(rep)
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continue
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write(delim)
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delim = delimnl
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self._format(ent, stream, indent,
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allowance if last else 1,
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context, level)
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def _repr(self, object, context, level):
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repr, readable, recursive = self.format(object, context.copy(),
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self._depth, level)
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if not readable:
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self._readable = False
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if recursive:
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self._recursive = True
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return repr
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def format(self, object, context, maxlevels, level):
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"""Format object for a specific context, returning a string
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and flags indicating whether the representation is 'readable'
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and whether the object represents a recursive construct.
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"""
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return _safe_repr(object, context, maxlevels, level)
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# Return triple (repr_string, isreadable, isrecursive).
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def _safe_repr(object, context, maxlevels, level):
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typ = type(object)
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if typ is str:
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if 'locale' not in _sys.modules:
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return repr(object), True, False
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if "'" in object and '"' not in object:
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closure = '"'
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quotes = {'"': '\\"'}
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else:
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closure = "'"
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quotes = {"'": "\\'"}
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qget = quotes.get
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sio = _StringIO()
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write = sio.write
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for char in object:
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if char.isalpha():
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write(char)
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else:
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write(qget(char, repr(char)[1:-1]))
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return ("%s%s%s" % (closure, sio.getvalue(), closure)), True, False
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r = getattr(typ, "__repr__", None)
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if issubclass(typ, dict) and r is dict.__repr__:
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if not object:
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return "{}", True, False
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objid = id(object)
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if maxlevels and level >= maxlevels:
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return "{...}", False, objid in context
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if objid in context:
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return _recursion(object), False, True
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context[objid] = 1
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readable = True
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recursive = False
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components = []
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append = components.append
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level += 1
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saferepr = _safe_repr
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items = sorted(object.items(), key=_safe_tuple)
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for k, v in items:
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krepr, kreadable, krecur = saferepr(k, context, maxlevels, level)
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vrepr, vreadable, vrecur = saferepr(v, context, maxlevels, level)
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append("%s: %s" % (krepr, vrepr))
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readable = readable and kreadable and vreadable
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if krecur or vrecur:
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recursive = True
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del context[objid]
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return "{%s}" % ", ".join(components), readable, recursive
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if (issubclass(typ, list) and r is list.__repr__) or \
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(issubclass(typ, tuple) and r is tuple.__repr__):
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if issubclass(typ, list):
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if not object:
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return "[]", True, False
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format = "[%s]"
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elif len(object) == 1:
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format = "(%s,)"
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else:
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if not object:
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return "()", True, False
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format = "(%s)"
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objid = id(object)
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if maxlevels and level >= maxlevels:
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return format % "...", False, objid in context
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if objid in context:
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return _recursion(object), False, True
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context[objid] = 1
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readable = True
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recursive = False
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components = []
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append = components.append
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level += 1
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for o in object:
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orepr, oreadable, orecur = _safe_repr(o, context, maxlevels, level)
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append(orepr)
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if not oreadable:
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readable = False
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if orecur:
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recursive = True
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del context[objid]
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return format % ", ".join(components), readable, recursive
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rep = repr(object)
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return rep, (rep and not rep.startswith('<')), False
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def _recursion(object):
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return ("<Recursion on %s with id=%s>"
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% (type(object).__name__, id(object)))
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def _perfcheck(object=None):
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import time
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if object is None:
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object = [("string", (1, 2), [3, 4], {5: 6, 7: 8})] * 100000
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p = PrettyPrinter()
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t1 = time.time()
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_safe_repr(object, {}, None, 0)
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t2 = time.time()
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p.pformat(object)
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t3 = time.time()
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print("_safe_repr:", t2 - t1)
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print("pformat:", t3 - t2)
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if __name__ == "__main__":
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_perfcheck()
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