traverseda
/
cpython
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Cleaner method naming convention

This commit is contained in:
Raymond Hettinger 2007-12-14 02:49:47 +00:00
parent 90e10e79ea
commit 42da874cdd
3 changed files with 30 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
Doc/library/collections.rst
View File

@ -368,8 +368,8 @@ they add the ability to access fields by name instead of position index.
can be specified as a list of strings (such as ['x', 'y']).
Any valid Python identifier may be used for a fieldname except for names
starting and ending with double underscores. Valid identifiers consist of
letters, digits, and underscores but do not start with a digit and cannot be
starting with an underscore. Valid identifiers consist of letters, digits,
and underscores but do not start with a digit or underscore and cannot be
a :mod:`keyword` such as *class*, *for*, *return*, *global*, *pass*, *print*,
or *raise*.
@ -386,15 +386,15 @@ Example::
class Point(tuple):
'Point(x, y)'
__slots__ = ()
__fields__ = ('x', 'y')
_fields = ('x', 'y')
def __new__(cls, x, y):
return tuple.__new__(cls, (x, y))
def __repr__(self):
return 'Point(x=%r, y=%r)' % self
def __asdict__(self):
def _asdict(self):
'Return a new dict mapping field names to their values'
return dict(zip(('x', 'y'), self))
def __replace__(self, **kwds):
def _replace(self, **kwds):
'Return a new Point object replacing specified fields with new values'
return Point(**dict(zip(('x', 'y'), self), **kwds))
x = property(itemgetter(0))
@ -444,40 +444,40 @@ When casting a dictionary to a named tuple, use the double-star-operator::
In addition to the methods inherited from tuples, named tuples support
two additonal methods and a read-only attribute.
.. method:: somenamedtuple.__asdict__()
.. method:: somenamedtuple._asdict()
Return a new dict which maps field names to their corresponding values:
::
>>> p.__asdict__()
>>> p._asdict()
{'x': 11, 'y': 22}
.. method:: somenamedtuple.__replace__(kwargs)
.. method:: somenamedtuple._replace(kwargs)
Return a new instance of the named tuple replacing specified fields with new values:
::
>>> p = Point(x=11, y=22)
>>> p.__replace__(x=33)
>>> p._replace(x=33)
Point(x=33, y=22)
>>> for partnum, record in inventory.items():
... inventory[partnum] = record.__replace__(price=newprices[partnum], updated=time.now())
... inventory[partnum] = record._replace(price=newprices[partnum], updated=time.now())
.. attribute:: somenamedtuple.__fields__
.. attribute:: somenamedtuple._fields
Return a tuple of strings listing the field names. This is useful for introspection
and for creating new named tuple types from existing named tuples.
::
>>> p.__fields__ # view the field names
>>> p._fields # view the field names
('x', 'y')
>>> Color = namedtuple('Color', 'red green blue')
>>> Pixel = namedtuple('Pixel', Point.__fields__ + Color.__fields__)
>>> Pixel = namedtuple('Pixel', Point._fields + Color._fields)
>>> Pixel(11, 22, 128, 255, 0)
Pixel(x=11, y=22, red=128, green=255, blue=0)'
@ -493,13 +493,13 @@ the :meth:`__repr__` method:
Point(10.000, 20.000)
Default values can be implemented by starting with a prototype instance
and customizing it with :meth:`__replace__`:
and customizing it with :meth:`_replace`:
::
>>> Account = namedtuple('Account', 'owner balance transaction_count')
>>> model_account = Account('<owner name>', 0.0, 0)
>>> johns_account = model_account.__replace__(owner='John')
>>> johns_account = model_account._replace(owner='John')
.. rubric:: Footnotes

14
Lib/collections.py
View File

@ -26,12 +26,12 @@ def namedtuple(typename, field_names, verbose=False):
(11, 22)
>>> p.x + p.y # fields also accessable by name
33
>>> d = p.__asdict__() # convert to a dictionary
>>> d = p._asdict() # convert to a dictionary
>>> d['x']
11
>>> Point(**d) # convert from a dictionary
Point(x=11, y=22)
>>> p.__replace__(x=100) # __replace__() is like str.replace() but targets named fields
>>> p._replace(x=100) # _replace() is like str.replace() but targets named fields
Point(x=100, y=22)
"""
@ -49,8 +49,8 @@ def namedtuple(typename, field_names, verbose=False):
raise ValueError('Type names and field names cannot start with a number: %r' % name)
seen_names = set()
for name in field_names:
if name.startswith('__') and name.endswith('__') and len(name) > 3:
raise ValueError('Field names cannot start and end with double underscores: %r' % name)
if name.startswith('_'):
raise ValueError('Field names cannot start with an underscore: %r' % name)
if name in seen_names:
raise ValueError('Encountered duplicate field name: %r' % name)
seen_names.add(name)
@ -61,15 +61,15 @@ def namedtuple(typename, field_names, verbose=False):
template = '''class %(typename)s(tuple):
'%(typename)s(%(argtxt)s)'
__slots__ = ()
__fields__ = property(lambda self: %(field_names)r)
_fields = property(lambda self: %(field_names)r)
def __new__(cls, %(argtxt)s):
return tuple.__new__(cls, (%(argtxt)s))
def __repr__(self):
return '%(typename)s(%(reprtxt)s)' %% self
def __asdict__(self, dict=dict, zip=zip):
def _asdict(self, dict=dict, zip=zip):
'Return a new dict mapping field names to their values'
return dict(zip(%(field_names)r, self))
def __replace__(self, **kwds):
def _replace(self, **kwds):
'Return a new %(typename)s object replacing specified fields with new values'
return %(typename)s(**dict(zip(%(field_names)r, self), **kwds)) \n''' % locals()
for i, name in enumerate(field_names):

16
Lib/test/test_collections.py
View File

@ -25,11 +25,11 @@ class TestNamedTuple(unittest.TestCase):
self.assertRaises(ValueError, namedtuple, 'abc', 'efg g%hi') # field with non-alpha char
self.assertRaises(ValueError, namedtuple, 'abc', 'abc class') # field has keyword
self.assertRaises(ValueError, namedtuple, 'abc', '8efg 9ghi') # field starts with digit
self.assertRaises(ValueError, namedtuple, 'abc', '__efg__ ghi') # field with double underscores
self.assertRaises(ValueError, namedtuple, 'abc', '_efg ghi') # field with leading underscore
self.assertRaises(ValueError, namedtuple, 'abc', 'efg efg ghi') # duplicate field
namedtuple('Point0', 'x1 y2') # Verify that numbers are allowed in names
namedtuple('_', '_ __ ___') # Verify that underscores are allowed
namedtuple('_', 'a b c') # Test leading underscores in a typename
def test_instance(self):
Point = namedtuple('Point', 'x y')
@ -46,17 +46,17 @@ class TestNamedTuple(unittest.TestCase):
self.assertEqual(repr(p), 'Point(x=11, y=22)')
self.assert_('__dict__' not in dir(p)) # verify instance has no dict
self.assert_('__weakref__' not in dir(p))
self.assertEqual(p.__fields__, ('x', 'y')) # test __fields__ attribute
self.assertEqual(p.__replace__(x=1), (1, 22)) # test __replace__ method
self.assertEqual(p.__asdict__(), dict(x=11, y=22)) # test __dict__ method
self.assertEqual(p._fields, ('x', 'y')) # test _fields attribute
self.assertEqual(p._replace(x=1), (1, 22)) # test _replace method
self.assertEqual(p._asdict(), dict(x=11, y=22)) # test _asdict method
# Verify that __fields__ is read-only
# Verify that _fields is read-only
try:
p.__fields__ = ('F1' ,'F2')
p._fields = ('F1' ,'F2')
except AttributeError:
pass
else:
self.fail('The __fields__ attribute needs to be read-only')
self.fail('The _fields attribute needs to be read-only')
# verify that field string can have commas
Point = namedtuple('Point', 'x, y')