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#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
"""A fast but lossy, totally generic object formatter."""
import types
EASY_TYPES = (type(None), int, long, float, bool)
META_TYPES = (type, types.ClassType)
STRING_TYPES = (str, unicode)
CONTAINER_TYPES = {tuple: ('(', ')'),
list: ('[', ']'),
dict: ('{', '}'),
}
BUILTIN_TYPES = EASY_TYPES + STRING_TYPES + tuple(CONTAINER_TYPES)
INSTANCE_TYPE = types.InstanceType
def format_value(val, limit=100, level=10):
"""Wrapper around _format_value()."""
return _format_value(val, limit, level)
def _format_value(val, limit, level, len=len, repr=repr):
"""Format an arbitrary value as a compact string.
This is a variant on Python's built-in repr() function, also
borrowing some ideas from the repr.py standard library module, but
tuned for speed even in extreme cases (like very large longs or very
long strings) and safety (it never invokes user code).
For structured data types like lists and objects it calls itself
recursively; recursion is strictly limited by level.
Python's basic types (numbers, strings, lists, tuples, dicts, bool,
and None) are represented using their familiar Python notations.
Objects are represented as ClassName<attr1=val1, attr2=val2, ...>.
Portions omitted due to the various limits are represented using
three dots ('...').
Args:
val: An arbitrary value.
limit: Limit on the output length.
level: Recursion level countdown.
len, repr: Not arguments; for optimization.
Returns:
A str instance.
"""
if level <= 0:
return '...'
typ = type(val)
if typ in EASY_TYPES:
if typ is float:
rep = str(val)
elif typ is long:
if val >= 10L**99:
return '...L'
elif val <= -10L**98:
return '-...L'
else:
rep = repr(val)
else:
rep = repr(val)
if typ is long and len(rep) > limit:
n1 = (limit - 3) // 2
n2 = (limit - 3) - n1
rep = rep[:n1] + '...' + rep[-n2:]
return rep
if typ in META_TYPES:
return val.__name__
if typ in STRING_TYPES:
n1 = (limit - 3) // 2
n2 = (limit - 3) - n1
if len(val) > limit:
head = repr(val[:n1])
tail = repr(val[-n2:])
return head[:n1] + '...' + tail[-n2:]
rep = repr(val)
if len(rep) <= limit:
return rep
return rep[:n1] + '...' + rep[-n2:]
if typ is types.MethodType:
if val.im_self is None:
fmt = '<unbound method %s of %s>'
else:
fmt = '<method %s of %s<>>'
return fmt % (val.__name__, val.im_class.__name__)
if typ is types.FunctionType:
nam = val.__name__
if nam == '<lambda>':
return nam
else:
return '<function %s>' % val.__name__
if typ is types.BuiltinFunctionType:
if val.__self__ is not None:
return '<built-in method %s of %s<>>' % (val.__name__,
val.__self__.__class__.__name__)
else:
return '<built-in function %s>' % val.__name__
if typ is types.ModuleType:
if hasattr(val, '__file__'):
return '<module %s>' % val.__name__
else:
return '<built-in module %s>' % val.__name__
if typ is types.CodeType:
return '<code object %s>' % val.co_name
dct = getattr(val, '__dict__', None)
if type(dct) is dict:
if typ is INSTANCE_TYPE:
typ = val.__class__
typnam = typ.__name__
priv = '_' + typnam + '__'
buffer = [typnam, '<']
limit -= len(buffer[0]) + 2
if len(dct) <= limit//4:
names = sorted(dct)
else:
names = list(dct)
append = buffer.append
first = True
if issubclass(typ, BUILTIN_TYPES):
for builtin_typ in BUILTIN_TYPES:
if issubclass(typ, builtin_typ):
try:
val = builtin_typ(val)
assert type(val) is builtin_typ
except Exception:
break
else:
append(_format_value(val, limit, level-1))
first = False
break
for nam in names:
if not isinstance(nam, basestring):
continue
if first:
first = False
else:
append(', ')
pnam = nam
if pnam.startswith(priv):
pnam = pnam[len(priv)-2:]
limit -= len(pnam) + 2
if limit <= 0:
append('...')
break
append(pnam)
append('=')
rep = _format_value(dct[nam], limit, level-1)
limit -= len(rep)
append(rep)
append('>')
return ''.join(buffer)
how = CONTAINER_TYPES.get(typ)
if how:
head, tail = how
buffer = [head]
append = buffer.append
limit -= 2
series = val
isdict = typ is dict
if isdict and len(val) <= limit//4:
series = sorted(val)
for elem in series:
if limit <= 0:
append('...')
break
rep = _format_value(elem, limit, level-1)
limit -= len(rep) + 2
append(rep)
if isdict:
rep = _format_value(val[elem], limit, level-1)
limit -= len(rep)
append(':')
append(rep)
append(', ')
if buffer[-1] == ', ':
if tail == ')' and len(val) == 1:
buffer[-1] = ',)'
else:
buffer[-1] = tail
else:
append(tail)
return ''.join(buffer)
if issubclass(typ, BUILTIN_TYPES):
for builtin_typ in BUILTIN_TYPES:
if issubclass(typ, builtin_typ):
try:
val = builtin_typ(val)
assert type(val) is builtin_typ
except Exception:
break
else:
typnam = typ.__name__
limit -= len(typnam) + 2
return '%s<%s>' % (typnam, _format_value(val, limit, level-1))
return typ.__name__ + '<>'
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