mirror of
https://github.com/kennethreitz/dive-into-python3.git
synced 2026-06-05 23:10:17 +00:00
some work on special method names
This commit is contained in:
Mark Pilgrim
+327
-96
@@ -5,105 +5,44 @@
|
||||
<!--[if IE]><script src=html5.js></script><![endif]-->
|
||||
<link rel=stylesheet type=text/css href=dip3.css>
|
||||
<style>
|
||||
body{counter-reset:h1 11}
|
||||
h1:before{counter-increment:h1;content:"Appendix B. "}
|
||||
h2:before{counter-increment:h2;content:"B." counter(h2) ". "}
|
||||
h3:before{counter-increment:h3;content:"B." counter(h2) "." counter(h3) ". "}
|
||||
tr + tr th:first-child{font:medium 'Arial Unicode MS',FreeSerif,OpenSymbol,'DejaVu Sans',sans-serif}
|
||||
table{width:100%;border-collapse:collapse}
|
||||
th,td{width:30%;padding:0 0.5em;border:1px solid #bbb}
|
||||
th{text-align:left;vertical-align:baseline}
|
||||
td{vertical-align:top}
|
||||
th:first-child{width:10%;text-align:center}
|
||||
th,td,td pre{margin:0}
|
||||
td pre{padding:0;border:0}
|
||||
</style>
|
||||
<link rel=stylesheet type=text/css media='only screen and (max-device-width: 480px)' href=mobile.css>
|
||||
</head>
|
||||
<form action=http://www.google.com/cse><div><input type=hidden name=cx value=014021643941856155761:l5eihuescdw><input type=hidden name=ie value=UTF-8> <input name=q size=25> <input type=submit name=sa value=Search></div></form>
|
||||
<p>You are here: <a href=index.html>Home</a> <span>‣</span> <a href=table-of-contents.html#special-method-names>Dive Into Python 3</a> <span>‣</span>
|
||||
<p id=level>Difficulty level: <span title=advanced>♦♦♦♦♢</span>
|
||||
<p id=level>Difficulty level: <span title=advanced>♦♦♦♦♦</span>
|
||||
<h1>Special Method Names</h1>
|
||||
<blockquote class=q>
|
||||
<p><span>❝</span> FIXME <span>❞</span><br>— FIXME
|
||||
</blockquote>
|
||||
<p id=toc>
|
||||
<h2 id=divingin>Diving In</h2>
|
||||
<h2 id=divingin>Diving in</h2>
|
||||
<p class=f>FIXME
|
||||
|
||||
<p class=d>[<a href=examples/ordereddict.py>download <code>ordereddict.py</code></a>]
|
||||
<pre><code>import collections
|
||||
import itertools
|
||||
|
||||
class OrderedDict(dict, collections.MutableMapping):
|
||||
|
||||
def __init__(self, *args, **kwds):
|
||||
if len(args) > 1:
|
||||
raise TypeError('expected at most 1 arguments')
|
||||
if not hasattr(self, '_keys'):
|
||||
self._keys = []
|
||||
self.update(*args, **kwds)
|
||||
|
||||
def clear(self):
|
||||
del self._keys[:]
|
||||
dict.clear(self)
|
||||
|
||||
def __setitem__(self, key, value):
|
||||
if key not in self:
|
||||
self._keys.append(key)
|
||||
dict.__setitem__(self, key, value)
|
||||
|
||||
def __delitem__(self, key):
|
||||
dict.__delitem__(self, key)
|
||||
self._keys.remove(key)
|
||||
|
||||
def __iter__(self):
|
||||
return iter(self._keys)
|
||||
|
||||
def __reversed__(self):
|
||||
return reversed(self._keys)
|
||||
|
||||
def popitem(self):
|
||||
if not self:
|
||||
raise KeyError('dictionary is empty')
|
||||
key = self._keys.pop()
|
||||
value = dict.pop(self, key)
|
||||
return key, value
|
||||
|
||||
def __reduce__(self):
|
||||
items = [[k, self[k]] for k in self]
|
||||
inst_dict = vars(self).copy()
|
||||
inst_dict.pop('_keys', None)
|
||||
return (self.__class__, (items,), inst_dict)
|
||||
|
||||
setdefault = MutableMapping.setdefault
|
||||
update = MutableMapping.update
|
||||
pop = MutableMapping.pop
|
||||
keys = MutableMapping.keys
|
||||
values = MutableMapping.values
|
||||
items = MutableMapping.items
|
||||
|
||||
def __repr__(self):
|
||||
if not self:
|
||||
return '%s()' % (self.__class__.__name__,)
|
||||
return '%s(%r)' % (self.__class__.__name__, list(self.items()))
|
||||
|
||||
def copy(self):
|
||||
return self.__class__(self)
|
||||
|
||||
@classmethod
|
||||
def fromkeys(cls, iterable, value=None):
|
||||
d = cls()
|
||||
for key in iterable:
|
||||
d[key] = value
|
||||
return d
|
||||
|
||||
def __eq__(self, other):
|
||||
if isinstance(other, OrderedDict):
|
||||
return all(p==q for p, q in itertools.zip_longest(self.items(), other.items()))
|
||||
return dict.__eq__(self, other)</code></pre>
|
||||
|
||||
<!--
|
||||
|
||||
Basics:
|
||||
<h2 id=basics>Basics</h2>
|
||||
|
||||
<pre>
|
||||
__init__ - covered in iterators.html
|
||||
__repr__ - covered in ordereddict.py
|
||||
__str__ - covered in fractions.py
|
||||
__bytes__ (*)
|
||||
__format__
|
||||
</pre>
|
||||
|
||||
Rich comparisons:
|
||||
<h2 id=rich-comparisons>Rich Comparisons</h2>
|
||||
|
||||
<pre>
|
||||
__lt__ - covered in fractions.py
|
||||
__le__ - covered in fractions.py
|
||||
__eq__ - covered in ordereddict.py, fractions.py
|
||||
@@ -112,41 +51,135 @@ __gt__ - covered in fractions.py
|
||||
__ge__ - covered in fractions.py
|
||||
__bool__ - covered in fractions.py
|
||||
__cmp__ (*)
|
||||
</pre>
|
||||
|
||||
Custom attributes:
|
||||
<h2 id=custom-attributes>Custom Attributes</h2>
|
||||
|
||||
<pre>
|
||||
__getattr__
|
||||
__getattribute__
|
||||
__setattr__
|
||||
__delattr__
|
||||
__dir__
|
||||
</pre>
|
||||
|
||||
Acts like a function:
|
||||
<h2 id=acts-like-function>Classes That Act Like Functions</h2>
|
||||
|
||||
<pre>
|
||||
__call__
|
||||
</pre>
|
||||
|
||||
Acts like a list:
|
||||
<h2 id=acts-like-list>Classes That Act Like Sequences</h2>
|
||||
|
||||
<p>FIXME sequence intro
|
||||
|
||||
<table>
|
||||
<tr><th>Notes
|
||||
<th>You Want…
|
||||
<th>So You Write…
|
||||
<th>And Python Calls…
|
||||
<tr><th>
|
||||
<td>length of a sequence
|
||||
<td><code>len(seq)</code>
|
||||
<td><code>seq.__len__()</code>
|
||||
<tr><th>
|
||||
<td>whether a sequence contains a specific value
|
||||
<td><code>x in seq</code>
|
||||
<td><code>seq.__contains__(<var>x</var>)</code>
|
||||
</table>
|
||||
|
||||
<!--
|
||||
__len__
|
||||
__reversed__ - covered in ordereddict.py
|
||||
__contains__
|
||||
__index__
|
||||
__getslice__ (*)
|
||||
-->
|
||||
|
||||
Acts like a dictionary:
|
||||
<h2 id=acts-like-dict>Classes That Act Like Dictionaries</h2>
|
||||
|
||||
<pre>
|
||||
__getitem__
|
||||
__setitem__ - covered in ordereddict.py
|
||||
__delitem__ - covered in ordereddict.py
|
||||
__missing__ (*)
|
||||
</pre>
|
||||
|
||||
Acts like an iterator:
|
||||
<h2 id=acts-like-iterator>Classes That Act Like Iterators</h2>
|
||||
|
||||
<!--
|
||||
<tr><th>
|
||||
<td>reversed sequence
|
||||
<td><code>reversed(seq)</code>
|
||||
<td><code>x.__reversed__()</code>
|
||||
-->
|
||||
<pre>
|
||||
__iter__ (*) - covered in iterators.html
|
||||
__next__ (*) - covered in iterators.html
|
||||
__reversed__ - covered in ordereddict.py
|
||||
</pre>
|
||||
|
||||
Acts like a number:
|
||||
<h2 id=acts-like-number>Classes That Act Like Numbers</h2>
|
||||
|
||||
<p>FIXME binary operator intro
|
||||
|
||||
<table>
|
||||
<tr><th>Notes
|
||||
<th>You Want…
|
||||
<th>So You Write…
|
||||
<th>And Python Calls…
|
||||
<tr><th>
|
||||
<td>addition
|
||||
<td><code>x + y</code>
|
||||
<td><code>x.__add__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>subtraction
|
||||
<td><code>x - y</code>
|
||||
<td><code>x.__sub__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>multiplication
|
||||
<td><code>x * y</code>
|
||||
<td><code>x.__mul__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>division
|
||||
<td><code>x / y</code>
|
||||
<td><code>x.__truediv__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>floor division
|
||||
<td><code>x // y</code>
|
||||
<td><code>x.__floordiv__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>modulo (remainder)
|
||||
<td><code>x % y</code>
|
||||
<td><code>x.__mod__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>floor division <i class=baa>&</i> modulo
|
||||
<td><code>divmod(x, y)</code>
|
||||
<td><code>x.__divmod__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>raise to power
|
||||
<td><code>x ** y</code>
|
||||
<td><code>x.__pow__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>left bit-shift
|
||||
<td><code>x << y</code>
|
||||
<td><code>x.__lshift__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>right bit-shift
|
||||
<td><code>x >> y</code>
|
||||
<td><code>x.__rshift__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>bitwise <code>and</code>
|
||||
<td><code>x & y</code>
|
||||
<td><code>x.__and__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>bitwise <code>xor</code>
|
||||
<td><code>x ^ y</code>
|
||||
<td><code>x.__xor__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>bitwise <code>or</code>
|
||||
<td><code>x | y</code>
|
||||
<td><code>x.__or__(<var>y</var>)</code>
|
||||
</table>
|
||||
|
||||
<!--
|
||||
__add__ - covered in fractions.py
|
||||
__sub__
|
||||
__mul__
|
||||
@@ -160,6 +193,70 @@ __rshift__
|
||||
__and__
|
||||
__xor__
|
||||
__or__
|
||||
-->
|
||||
|
||||
<p>FIXME explain circumstances under which reflected methods will be called. <!-- If <var>x</var> doesn't implement a given special method, or if it implements it but return <code>NotImplemented</code>, the Python interpreter will try a different approach — calling a special method on <var>y</var> instead of <var>x</var>.-->
|
||||
|
||||
<table>
|
||||
<tr><th>Notes
|
||||
<th>You Want…
|
||||
<th>So You Write…
|
||||
<th>And Python Calls…
|
||||
<tr><th>
|
||||
<td>addition
|
||||
<td><code>x + y</code>
|
||||
<td><code>y.__radd__(<var>x</var>)</code>
|
||||
<tr><th>
|
||||
<td>subtraction
|
||||
<td><code>x - y</code>
|
||||
<td><code>y.__rsub__(<var>x</var>)</code>
|
||||
<tr><th>
|
||||
<td>multiplication
|
||||
<td><code>x * y</code>
|
||||
<td><code>y.__rmul__(<var>x</var>)</code>
|
||||
<tr><th>
|
||||
<td>division
|
||||
<td><code>x / y</code>
|
||||
<td><code>y.__rtruediv__(<var>x</var>)</code>
|
||||
<tr><th>
|
||||
<td>floor division
|
||||
<td><code>x // y</code>
|
||||
<td><code>y.__rfloordiv__(<var>x</var>)</code>
|
||||
<tr><th>
|
||||
<td>modulo (remainder)
|
||||
<td><code>x % y</code>
|
||||
<td><code>y.__rmod__(<var>x</var>)</code>
|
||||
<tr><th>
|
||||
<td>floor division <i class=baa>&</i> modulo
|
||||
<td><code>divmod(x, y)</code>
|
||||
<td><code>y.__rdivmod__(<var>x</var>)</code>
|
||||
<tr><th>
|
||||
<td>raise to power
|
||||
<td><code>x ** y</code>
|
||||
<td><code>y.__rpow__(<var>x</var>)</code>
|
||||
<tr><th>
|
||||
<td>left bit-shift
|
||||
<td><code>x << y</code>
|
||||
<td><code>y.__rlshift__(<var>x</var>)</code>
|
||||
<tr><th>
|
||||
<td>right bit-shift
|
||||
<td><code>x >> y</code>
|
||||
<td><code>y.__rrshift__(<var>x</var>)</code>
|
||||
<tr><th>
|
||||
<td>bitwise <code>and</code>
|
||||
<td><code>x & y</code>
|
||||
<td><code>y.__rand__(<var>x</var>)</code>
|
||||
<tr><th>
|
||||
<td>bitwise <code>xor</code>
|
||||
<td><code>x ^ y</code>
|
||||
<td><code>y.__rxor__(<var>x</var>)</code>
|
||||
<tr><th>
|
||||
<td>bitwise <code>or</code>
|
||||
<td><code>x | y</code>
|
||||
<td><code>y.__ror__(<var>x</var>)</code>
|
||||
</table>
|
||||
|
||||
<!--
|
||||
__radd__ - covered in fractions.py
|
||||
__rsub__
|
||||
__rmul__
|
||||
@@ -172,6 +269,66 @@ __rrshift__
|
||||
__rand__
|
||||
__rxor__
|
||||
__ror__
|
||||
-->
|
||||
|
||||
<p>FIXME explain in-place augmented assignments
|
||||
|
||||
<table>
|
||||
<tr><th>Notes
|
||||
<th>You Want…
|
||||
<th>So You Write…
|
||||
<th>And Python Calls…
|
||||
<tr><th>
|
||||
<td>in-place addition
|
||||
<td><code>x += y</code>
|
||||
<td><code>x.__iadd__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>in-place subtraction
|
||||
<td><code>x -= y</code>
|
||||
<td><code>x.__isub__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>in-place multiplication
|
||||
<td><code>x *= y</code>
|
||||
<td><code>x.__imul__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>in-place division
|
||||
<td><code>x /= y</code>
|
||||
<td><code>x.__itruediv__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>in-place floor division
|
||||
<td><code>x //= y</code>
|
||||
<td><code>x.__ifloordiv__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>in-place modulo
|
||||
<td><code>x %= y</code>
|
||||
<td><code>x.__imod__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>in-place raise to power
|
||||
<td><code>x **= y</code>
|
||||
<td><code>x.__ipow__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>in-place left bit-shift
|
||||
<td><code>x <<= y</code>
|
||||
<td><code>x.__ilshift__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>in-place right bit-shift
|
||||
<td><code>x >>= y</code>
|
||||
<td><code>x.__irshift__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>in-place bitwise <code>and</code>
|
||||
<td><code>x &= y</code>
|
||||
<td><code>x.__iand__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>in-place bitwise <code>xor</code>
|
||||
<td><code>x ^= y</code>
|
||||
<td><code>x.__ixor__(<var>y</var>)</code>
|
||||
<tr><th>
|
||||
<td>in-place bitwise <code>or</code>
|
||||
<td><code>x |= y</code>
|
||||
<td><code>x.__ior__(<var>y</var>)</code>
|
||||
</table>
|
||||
|
||||
<!--
|
||||
__iadd__
|
||||
__isub__
|
||||
__imul__
|
||||
@@ -184,6 +341,70 @@ __irshift__
|
||||
__iand__
|
||||
__ixor__
|
||||
__ior__
|
||||
-->
|
||||
|
||||
<p>FIXME unary operator intro
|
||||
|
||||
<table>
|
||||
<tr><th>Notes
|
||||
<th>You Want…
|
||||
<th>So You Write…
|
||||
<th>And Python Calls…
|
||||
<tr><th>
|
||||
<td>negative number
|
||||
<td><code>-x</code>
|
||||
<td><code>x.__neg__()</code>
|
||||
<tr><th>
|
||||
<td>positive number
|
||||
<td><code>+x</code>
|
||||
<td><code>x.__pos__()</code>
|
||||
<tr><th>
|
||||
<td>absolute value
|
||||
<td><code>abs(x)</code>
|
||||
<td><code>x.__abs__()</code>
|
||||
<tr><th>
|
||||
<td>inverse
|
||||
<td><code>~x</code>
|
||||
<td><code>x.__invert__()</code>
|
||||
<tr><th>
|
||||
<td>complex number
|
||||
<td><code>complex(x)</code>
|
||||
<td><code>x.__complex__()</code>
|
||||
<tr><th>
|
||||
<td>integer
|
||||
<td><code>int(x)</code>
|
||||
<td><code>x.__int__()</code>
|
||||
<tr><th>
|
||||
<td>floating point number
|
||||
<td><code>float(x)</code>
|
||||
<td><code>x.__float__()</code>
|
||||
<tr><th>
|
||||
<td>number rounded to nearest integer
|
||||
<td><code>round(x)</code>
|
||||
<td><code>x.__round__()</code>
|
||||
<tr><th>
|
||||
<td>number rounded to nearest <var>n</var> digits
|
||||
<td><code>round(x, n)</code>
|
||||
<td><code>x.__round__(n)</code>
|
||||
<tr><th>
|
||||
<td>smallest integer <code>>= x</code>
|
||||
<td><code>math.ceil(x)</code>
|
||||
<td><code>x.__ceil__()</code>
|
||||
<tr><th>
|
||||
<td>largest integer <code><= x</code>
|
||||
<td><code>math.floor(x)</code>
|
||||
<td><code>x.__floor__()</code>
|
||||
<tr><th>
|
||||
<td>truncate <code>x</code> to nearest integer toward <code>0</code>
|
||||
<td><code>math.trunc(x)</code>
|
||||
<td><code>x.__trunc__()</code>
|
||||
<tr><th>
|
||||
<td>???
|
||||
<td><code>???</code>
|
||||
<td><code>x.__index__()</code>
|
||||
</table>
|
||||
|
||||
<!--
|
||||
__neg__ - covered in fractions.py
|
||||
__pos__ - covered in fractions.py
|
||||
__abs__ - covered in fractions.py
|
||||
@@ -191,13 +412,17 @@ __invert__
|
||||
__complex__
|
||||
__int__
|
||||
__float__
|
||||
__long__ (*)
|
||||
__round__ - covered in fractions.py
|
||||
__ceil__ (*) - covered in fractions.py
|
||||
__floor__ (*) - covered in fractions.py
|
||||
__trunc__ (*) - covered in fractions.py
|
||||
__index__
|
||||
-->
|
||||
|
||||
Support for pickling, see http://docs.python.org/3.0/library/pickle.html:
|
||||
<h2 id=pickle>Support For Pickling</h2>
|
||||
|
||||
<pre>
|
||||
see http://docs.python.org/3.0/library/pickle.html:
|
||||
|
||||
__copy__ (*) - covered in fractions.py
|
||||
__deepcopy__ (*) - covered in fractions.py
|
||||
@@ -207,9 +432,18 @@ __getstate__ (*)
|
||||
__setstate__ (*)
|
||||
__reduce__ (*) - covered in ordereddict.py, fractions.py
|
||||
__reduce_ex__ (*)
|
||||
</pre>
|
||||
|
||||
Really weird stuff:
|
||||
<h2 id=context-managers>Classes That Can Be Used in a <code>with</code> Block</h2>
|
||||
|
||||
<pre>
|
||||
__enter__ see http://docs.python.org/3.0/library/stdtypes.html#typecontextmanager
|
||||
__exit__
|
||||
</pre>
|
||||
|
||||
<h2 id=esoterica>Really Esoteric Stuff</h2>
|
||||
|
||||
<pre>
|
||||
__new__ - covered in fractions.py
|
||||
__del__
|
||||
__slots__
|
||||
@@ -217,15 +451,12 @@ __hash__ - covered in fractions.py
|
||||
__get__
|
||||
__set__
|
||||
__delete__
|
||||
__enter__ see http://docs.python.org/3.0/library/stdtypes.html#typecontextmanager
|
||||
__exit__
|
||||
__subclasshook__ (*) see http://docs.python.org/3.0/library/abc.html
|
||||
__instancecheck__ (*) see http://www.ibm.com/developerworks/linux/library/l-python3-2/
|
||||
__subclasscheck__ (*)
|
||||
</pre>
|
||||
|
||||
-->
|
||||
|
||||
<p class=nav><a rel=prev class=todo><span>☜</a> <a rel=next class=todo><span>☞</span></a>
|
||||
<p class=nav><a rel=prev href=porting-code-to-python-3-with-2to3.html title="back to “Porting code to Python 3 with 2to3”"><span>☜</span></a> <a rel=next class=todo><span>☞</span></a>
|
||||
<p class=c>© 2001–9 <a href=about.html>Mark Pilgrim</a>
|
||||
<script src=jquery.js></script>
|
||||
<script src=dip3.js></script>
|
||||
|
||||
Reference in New Issue
Block a user