mirror of https://github.com/python/cpython
pprint's workhorse _safe_repr() function took time quadratic in the # of
elements when crunching a list, dict or tuple. Now takes linear time instead -- huge speedup for even moderately large containers, and the code is notably simpler too. Added some basic "is the output correct?" tests to test_pprint.
This commit is contained in:
Tim Peters
parent
43913dd27c
commit
95b3f78622
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@ -188,66 +188,55 @@ class PrettyPrinter:
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# Return triple (repr_string, isreadable, isrecursive).
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def _safe_repr(object, context, maxlevels=None, level=0):
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level = level + 1
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level += 1
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typ = type(object)
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if not (typ in (DictType, ListType, TupleType) and object):
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rep = `object`
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return rep, (rep and (rep[0] != '<')), 0
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if context.has_key(id(object)):
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return `_Recursion(object)`, 0, 1
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objid = id(object)
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context[objid] = 1
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readable = 1
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recursive = 0
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if typ is DictType:
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if maxlevels and level >= maxlevels:
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s = "{...}"
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readable = 0
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else:
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items = object.items()
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k, v = items[0]
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startchar, endchar = {ListType: "[]",
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TupleType: "()",
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DictType: "{}"}[typ]
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if maxlevels and level > maxlevels:
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with_commas = "..."
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readable = 0
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elif typ is DictType:
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components = []
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for k, v in object.iteritems():
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krepr, kreadable, krecur = _safe_repr(k, context, maxlevels,
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level)
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vrepr, vreadable, vrecur = _safe_repr(v, context, maxlevels,
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level)
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components.append("%s: %s" % (krepr, vrepr))
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readable = readable and kreadable and vreadable
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recursive = recursive or krecur or vrecur
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s = "{%s: %s" % (krepr, vrepr)
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for k, v in items[1:]:
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krepr, kreadable, krecur = _safe_repr(k, context, maxlevels,
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level)
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vrepr, vreadable, vrecur = _safe_repr(v, context, maxlevels,
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level)
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readable = readable and kreadable and vreadable
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recursive = recursive or krecur or vrecur
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s = "%s, %s: %s" % (s, krepr, vrepr)
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s = s + "}"
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else:
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s, term = (typ is ListType) and ('[', ']') or ('(', ')')
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if maxlevels and level >= maxlevels:
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s = s + "..."
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readable = 0
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else:
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with_commas = ", ".join(components)
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else: # list or tuple
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assert typ in (ListType, TupleType)
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components = []
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for element in object:
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subrepr, subreadable, subrecur = _safe_repr(
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object[0], context, maxlevels, level)
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element, context, maxlevels, level)
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components.append(subrepr)
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readable = readable and subreadable
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recursive = recursive or subrecur
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s = s + subrepr
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tail = object[1:]
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if not tail:
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if typ is TupleType:
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s = s + ','
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for ent in tail:
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subrepr, subreadable, subrecur = _safe_repr(
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ent, context, maxlevels, level)
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readable = readable and subreadable
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recursive = recursive or subrecur
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s = "%s, %s" % (s, subrepr)
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s = s + term
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if len(components) == 1 and typ is TupleType:
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components[0] += ","
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with_commas = ", ".join(components)
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s = "%s%s%s" % (startchar, with_commas, endchar)
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del context[objid]
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return s, readable and not recursive, recursive
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class _Recursion:
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# represent a recursive relationship; really only used for the __repr__()
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# method...
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@ -12,7 +12,7 @@ class QueryTestCase(unittest.TestCase):
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self.a[-12] = self.b
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def test_basic(self):
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# Verify that .isrecursive() and .isreadable() work.
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# Verify that .isrecursive() and .isreadable() work w/o recursion.
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verify = self.assert_
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for safe in (2, 2.0, 2j, "abc", [3], (2,2), {3: 3}, u"yaddayadda",
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self.a, self.b):
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@ -22,6 +22,7 @@ class QueryTestCase(unittest.TestCase):
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"expected isreadable for " + `safe`)
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def test_knotted(self):
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# Verify that .isrecursive() and .isreadable() work w/ recursion.
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# Tie a knot.
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self.b[67] = self.a
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# Messy dict.
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@ -54,5 +55,20 @@ class QueryTestCase(unittest.TestCase):
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verify(not pprint.isreadable(unreadable),
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"expected not isreadable for " + `unreadable`)
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def test_same_as_repr(self):
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"Simple objects and small containers that should be same as repr()."
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verify = self.assert_
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for simple in (0, 0L, 0+0j, 0.0, "", u"", (), [], {}, verify, pprint,
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-6, -6L, -6-6j, -1.5, "x", u"x", (3,), [3], {3: 6},
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(1,2), [3,4], {5: 6, 7: 8},
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{"xy\tab\n": (3,), 5: [[]], (): {}},
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range(10, -11, -1)
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):
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native = repr(simple)
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for function in "pformat", "saferepr":
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f = getattr(pprint, function)
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got = f(simple)
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verify(native == got, "expected %s got %s from pprint.%s" %
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(native, got, function))
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test_support.run_unittest(QueryTestCase)
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@ -92,6 +92,8 @@ Library
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- pprint.isrecursive(object) didn't correctly identify recursive objects.
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Now it does.
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- pprint functions now much faster for large containers (tuple, list, dict).
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Tests
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- New test_mutants.py runs dict comparisons where the key and value
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@ -100,7 +102,8 @@ Tests
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of heart: it can also cause Win9x to freeze or reboot!).
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- New test_pprint.py verfies that pprint.isrecursive() and
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pprint.isreadable() return sensible results.
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pprint.isreadable() return sensible results. Also verifies that simple
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cases produce correct output.
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What's New in Python 2.1 (final)?
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