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Using property() on classmethods
...te the property on the metaclass.
>>> class foo(object):
... _var = 5
... class __metaclass__(type): # Python 2 syntax for metaclasses
... pass
... @classmethod
... def getvar(cls):
... return cls._var
... @classmethod
... def setvar(cls, value):
.....
When is “i += x” different from “i = i + x” in Python?
...
This depends entirely on the object i.
+= calls the __iadd__ method (if it exists -- falling back on __add__ if it doesn't exist) whereas + calls the __add__ method1 or the __radd__ method in a few cases2.
From an API perspective, __iadd__ is supposed to be used for modifyi...
编译失败！ Error: Your build failed due to an error in the AAPT stage,...
...tivity> attribute name has invalid character
[java] /tmp/1685410160630_0.39828964915976717-0/youngandroidproject/../build/AndroidManifest.xml:5: Tag <activity> attribute name has invalid character '�'.
[java] May 30, 2023 9:29:27 AM com.google.appinventor.build...
How do I create a namespace package in Python?
...
TL;DR:
On Python 3.3 you don't have to do anything, just don't put any __init__.py in your namespace package directories and it will just work. On pre-3.3, choose the pkgutil.extend_path() solution over the pkg_resources.declare_namespace() one, because it's future-proof and already compatible w...
How to use a dot “.” to access members of dictionary?
...ope to help you:
class Map(dict):
"""
Example:
m = Map({'first_name': 'Eduardo'}, last_name='Pool', age=24, sports=['Soccer'])
"""
def __init__(self, *args, **kwargs):
super(Map, self).__init__(*args, **kwargs)
for arg in args:
if isinstance(arg, dict...
Ignore python multiple return value
...
One common convention is to use a "_" as a variable name for the elements of the tuple you wish to ignore. For instance:
def f():
return 1, 2, 3
_, _, x = f()
share
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What is __future__ in Python used for and how/when to use it, and how it works
__future__ frequently appears in Python modules. I do not understand what __future__ is for and how/when to use it even after reading the Python's __future__ doc .
...
How to return a value from __init__ in Python?
I have a class with an __init__ function.
10 Answers
10
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What are some (concrete) use-cases for metaclasses?
...ate methods, than to do something like:
class PlottingInteractive:
add_slice = wrap_pylab_newplot(add_slice)
This method doesn't keep up with API changes and so on, but one that iterates over the class attributes in __init__ before re-setting the class attributes is more efficient and keeps t...
Understanding the main method of python [duplicate]
...is almost unique to the language(*).
The semantics are a bit subtle. The __name__ identifier is bound to the name of any module as it's being imported. However, when a file is being executed then __name__ is set to "__main__" (the literal string: __main__).
This is almost always used to separate...