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310 lines
10 KiB
Python
310 lines
10 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.sydout].
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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 sys as _sys
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from cStringIO import StringIO as _StringIO
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__all__ = ["pprint","pformat","isreadable","isrecursive","saferepr",
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"PrettyPrinter"]
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# cache these for faster access:
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_commajoin = ", ".join
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_id = id
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_len = len
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_type = type
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def pprint(object, stream=None):
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"""Pretty-print a Python object to a stream [default is sys.sydout]."""
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printer = PrettyPrinter(stream=stream)
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printer.pprint(object)
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def pformat(object):
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"""Format a Python object into a pretty-printed representation."""
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return PrettyPrinter().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 PrettyPrinter:
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def __init__(self, indent=1, width=80, depth=None, stream=None):
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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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"""
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indent = int(indent)
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width = int(width)
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assert indent >= 0
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assert depth is None or depth > 0, "depth must be > 0"
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assert width
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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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def pprint(self, object):
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self._stream.write(self.pformat(object) + "\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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level = level + 1
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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 - 1)
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typ = _type(object)
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sepLines = _len(rep) > (self._width - 1 - indent - allowance)
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write = stream.write
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if sepLines:
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if typ is dict:
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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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context[objid] = 1
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indent = indent + self._indent_per_level
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items = object.items()
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items.sort()
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key, ent = items[0]
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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 + 1, context, level)
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if length > 1:
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for key, ent in items[1:]:
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rep = self._repr(key, context, level)
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write(',\n%s%s: ' % (' '*indent, rep))
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self._format(ent, stream, indent + _len(rep) + 2,
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allowance + 1, context, level)
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indent = indent - self._indent_per_level
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del context[objid]
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write('}')
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return
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if typ is list or typ is tuple:
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if typ is list:
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write('[')
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endchar = ']'
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else:
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write('(')
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endchar = ')'
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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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context[objid] = 1
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indent = indent + self._indent_per_level
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self._format(object[0], stream, indent, allowance + 1,
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context, level)
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if length > 1:
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for ent in object[1:]:
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write(',\n' + ' '*indent)
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self._format(ent, stream, indent,
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allowance + 1, context, level)
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indent = indent - self._indent_per_level
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del context[objid]
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if typ is tuple and length == 1:
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write(',')
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write(endchar)
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return
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write(rep)
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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 `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, `char`[1:-1]))
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return ("%s%s%s" % (closure, sio.getvalue(), closure)), True, False
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if typ is dict:
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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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for k, v in object.iteritems():
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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}" % _commajoin(components), readable, recursive
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if typ is list or typ is tuple:
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if typ is 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 % _commajoin(components), readable, recursive
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rep = `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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