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Checking if an instance's class implements an interface?
...
As therefromhere points out, you can use class_implements(). Just as with Reflection, this allows you to specify the class name as a string and doesn't require an instance of the class:
interface IInterface
{
}
class TheClass implements IInterface
{
}
$interfaces = cl...
How do I implement __getattribute__ without an infinite recursion error?
...n a class, but return all others normally. How do I accomplish this with __getattribute__ ?
6 Answers
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Can modules have properties the same way that objects can?
...ance. So, for example, your m.py module file could be:
import sys
class _M(object):
def __init__(self):
self.c = 0
def afunction(self):
self.c += 1
return self.c
y = property(afunction)
sys.modules[__name__] = _M()
...
Difference between __str__ and __repr__?
What is the difference between __str__ and __repr__ in Python?
23 Answers
23
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How to find all the subclasses of a class given its name?
...ses (i.e. subclassed from object, which is the default in Python 3) have a __subclasses__ method which returns the subclasses:
class Foo(object): pass
class Bar(Foo): pass
class Baz(Foo): pass
class Bing(Bar): pass
Here are the names of the subclasses:
print([cls.__name__ for cls in Foo.__subcla...
Difference between len() and .__len__()?
Is there any difference between calling len([1,2,3]) or [1,2,3].__len__() ?
4 Answers
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What is a “callable”?
...allable is anything that can be called.
The built-in callable (PyCallable_Check in objects.c) checks if the argument is either:
an instance of a class with a __call__ method or
is of a type that has a non null tp_call (c struct) member which indicates callability otherwise (such as in functions,...
what does the __file__ variable mean/do?
...
When a module is loaded from a file in Python, __file__ is set to its path. You can then use that with other functions to find the directory that the file is located in.
Taking your examples one at a time:
A = os.path.join(os.path.dirname(__file__), '..')
# A is the par...
How to create a custom string representation for a class object?
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Implement __str__() or __repr__() in the class's metaclass.
class MC(type):
def __repr__(self):
return 'Wahaha!'
class C(object):
__metaclass__ = MC
print C
Use __str__ if you mean a readable stringification, use __repr__ fo...
What does __FILE__ mean in Ruby?
...
It is a reference to the current file name. In the file foo.rb, __FILE__ would be interpreted as "foo.rb".
Edit: Ruby 1.9.2 and 1.9.3 appear to behave a little differently from what Luke Bayes said in his comment. With these files:
# test.rb
puts __FILE__
require './dir2/test.rb'
# di...