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Why do some functions have underscores “__” before and after the function name?
...gnized (these can generally be combined with any case convention):
_single_leading_underscore: weak "internal use" indicator. E.g. from M import * does not import objects whose name starts with an underscore.
single_trailing_underscore_: used by convention to avoid conflicts with Python ke...
How to add property to a class dynamically?
...ibute, on a given class. Kinda like a way to factor a huge if tree out of __getattribute__.
When I ask for foo.b in the example above, Python sees that the b defined on the class implements the descriptor protocol—which just means it's an object with a __get__, __set__, or __delete__ method. Th...
python NameError: global name '__file__' is not defined
...
This error comes when you append this line os.path.join(os.path.dirname(__file__)) in python interactive shell.
Python Shell doesn't detect current file path in __file__ and it's related to your filepath in which you added this line
So you should write this line os.path.join(os.path.dirname(__...
布局列表框循序渐进：从商品清单到购物车和网络分页 · App Inventor 2 中文网
...滚动。
第 1–6、9 关使用同一个列表实例：布局列表框_商品，宽、高均为填充父级，方向纵向，列数 1，空提示文本为“没有匹配的商品”。搜索和操作条放在列表外面。
在列表里面直接拖入 竖直布局_商品行，宽填充父级...
How to decorate a class?
...r specific scenario, YMMV :-)
What you're thinking of is a metaclass. The __new__ function in a metaclass is passed the full proposed definition of the class, which it can then rewrite before the class is created. You can, at that time, sub out the constructor for a new one.
Example:
def substitu...
What exactly are iterator, iterable, and iteration?
...and iterator have specific meanings.
An iterable is an object that has an __iter__ method which returns an iterator, or which defines a __getitem__ method that can take sequential indexes starting from zero (and raises an IndexError when the indexes are no longer valid). So an iterable is an object...
Standard way to embed version into python package?
...Not directly an answer to your question, but you should consider naming it __version__, not version.
This is almost a quasi-standard. Many modules in the standard library use __version__, and this is also used in lots of 3rd-party modules, so it's the quasi-standard.
Usually, __version__ is a stri...
Get name of current script in Python
...
You can use __file__ to get the name of the current file. When used in the main module, this is the name of the script that was originally invoked.
If you want to omit the directory part (which might be present), you can use os.path.bas...
Bidirectional 1 to 1 Dictionary in C#
...gt;, IDictionary
{
private readonly IDictionary<TFirst, TSecond> _firstToSecond = new Dictionary<TFirst, TSecond>();
[NonSerialized]
private readonly IDictionary<TSecond, TFirst> _secondToFirst = new Dictionary<TSecond, TFirst>();
[NonSerialized]
private r...
How can you set class attributes from variable arguments (kwargs) in python
...
You could update the __dict__ attribute (which represents the class attributes in the form of a dictionary) with the keyword arguments:
class Bar(object):
def __init__(self, **kwargs):
self.__dict__.update(kwargs)
then you can:
&g...