Magic methods are implicitly invoked by a programming language when some event or language construct is used.
Questions tagged [magic-methods]
616 questions
59
votes
10 answers
Where is the Python documentation for the special methods? (__init__, __new__, __len__, ...)
Where is a complete list of the special double-underscore/dunder methods that can be used in classes? (e.g., __init__, __new__, __len__, __add__)
mk12
- 25,873
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52
votes
1 answer
How to overload Python's __bool__ method in 2.x?
I thought this should print "False", why is it printing "True"?
>>> class Foo(object):
... def __bool__(self):
... return False
...
>>> f = Foo()
>>> if f:
... print "True"
... else:
... print "False"
...
True
>>>
dividebyzero
- 1,243
- 2
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47
votes
5 answers
Use of PHP Magic Methods __sleep and __wakeup
What is the use of the __sleep and __wakeup magic methods in PHP? I read the PHP documentation but it's still not clear:
class sleepWakeup {
public function __construct() {
// constructor //
}
public function __sleep() {
…
Madan Sapkota
- 25,047
- 11
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40
votes
7 answers
PHP 5.3 Magic Method __invoke
This topic expands on When do/should I use __construct(), __get(), __set(), and __call() in PHP? which talks about the __construct, __get and __set magic methods.
As of PHP 5.3 there is a new Magic Method called __invoke. The __invoke method is…
user83632
37
votes
4 answers
Are Magic Methods Best practice in PHP?
Are Magic Methods Best practice in PHP?
OM The Eternity
- 15,694
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- 182
35
votes
2 answers
Is it possible, using PHPUnit mock objects, to expect a call to a magic __call() method?
I've got a mock object in a test. The real object, PageRepository, implements a magic method using __call(), so if you call $pageRepository->findOneByXXXX($value_of_field_XXXX), it will search the database for records matching that parameter.
Is…
Jeremy Warne
- 3,437
- 2
- 30
- 28
31
votes
2 answers
Why does calling Python's 'magic method' not do type conversion like it would for the corresponding operator?
When I subtract a float from an integer (e.g. 1-2.0), Python does implicit type conversion (I think). But when I call what I thought was the same operation using the magic method __sub__, it suddenly does not anymore.
What am I missing here? When I…
doppler
- 997
- 5
- 17
30
votes
6 answers
Why does print(t) error if t.__str__() returns a non-string, but not print(t.__str__())?
I am trying to understand the __str__ method in Python.
class Test:
def __str__(self):
return 5
t = Test()
print(t.__str__())
In this method it returns an integer value but the print method is able to print it.
But, when I tried…
Manoj Ariyarathna
- 417
- 4
- 8
30
votes
6 answers
__new__ method giving error object.__new__() takes exactly one argument (the type to instantiate)
why the following code is giving error?
class Foo:
def __new__(cls, *args, **kwargs):
print("Creating Instance")
instance = super(Foo, cls).__new__(cls,*args, **kwargs)
return instance
def __init__(self, a, b):
…
Danish Mahmood
- 487
- 1
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- 9
27
votes
1 answer
Which Python dunder/magic methods do you need to implement to correctly proxy an object?
I'm trying to create an object proxy.
Attribute/property lookup can be done by simply implementing the __getattribute__, __setattr__ and __delattr__ methods.
However, other functionalities like len(x), x[], bool(x) require other dunder methods like…
Pragy Agarwal
- 578
- 1
- 8
- 22
26
votes
3 answers
Is there a way to return a custom value for min and max in Python?
I have a custom class,
class A:
def __init__(self, a, b):
self.a = a
self.b = b
The class is not iterable or indexable or anything like that. If at all possible, I would like to keep it that way. Is it possible to have something…
Mad Physicist
- 107,652
- 25
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25
votes
3 answers
Python __index__ special method
>>> class Thing(object):
... def __index__(self):
... return 1
...
>>> thing = Thing()
>>> list_ = ['abc', 'def', 'ghi']
>>> list_[thing]
'def'
>>> dict_ = {1: 'potato'}
>>> dict_[thing]
# KeyError
How does thing know to represent…
wim
- 338,267
- 99
- 616
- 750
25
votes
2 answers
PHP Child class Magic __isset works but __get doesn't
I have an abstract parent class Mongo_Document (from mongodb-php-odm) and an inherited class Model_ActionPlan. Mongo_Document has magic __isset and __get methods that interact with an array inside the Mongo_Document class.
I am trying to use the…
Moshe Katz
- 15,992
- 7
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- 116
24
votes
4 answers
Assigning vs. Defining Python Magic Methods
Consider the following abhorrent class:
class MapInt:
__call__ = int
def __sub__(self, other):
return map(self, other)
__add__ = map
One can then call map(int, lst) via MapInt() - lst, i.e.
assert list(MapInt() -…
kg583
- 408
- 2
- 8
21
votes
2 answers
How to write a static python getitem method?
What do I need to change to make this work?
class A:
@staticmethod
def __getitem__(val):
return "It works"
print A[0]
Note that I am calling the __getitem__ method on the type A.
Woltan
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