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What is the difference between __init__ and __call__?
I want to know the difference between __init__ and __call__ methods.
13 Answers
...
List attributes of an object
...
>>> class new_class():
... def __init__(self, number):
... self.multi = int(number) * 2
... self.str = str(number)
...
>>> a = new_class(2)
>>> a.__dict__
{'multi': 4, 'str': '2'}
>>> a.__dict__.keys(...
Get exception description and stack trace which caused an exception, all as a string
...
See the traceback module, specifically the format_exc() function. Here.
import traceback
try:
raise ValueError
except ValueError:
tb = traceback.format_exc()
else:
tb = "No error"
finally:
print tb
...
How to make an immutable object in Python?
...utable object in Python could be slightly tricky. You can't just override __setattr__ , because then you can't even set attributes in the __init__ . Subclassing a tuple is a trick that works:
...
Inverse dictionary lookup in Python
...s slow as yours, because it creates a list from the dict twice.
key = dict_obj.keys()[dict_obj.values().index(value)]
Or if you prefer brevity over readability you can save one more character with
key = list(dict_obj)[dict_obj.values().index(value)]
And if you prefer efficiency, @PaulMcGuire's...
KIO4_Gradient 拓展：布局中的颜色渐变 - App Inventor 2 中文网 - 清泛IT...
http://kio4.com/appinventor/287_extension_gradiente_color.htm
- 让我们看一下在布局中制作颜色渐变的扩展。- 我们放置一个布局，然后在该扩展的块中插入该布局的名称，放置一个包含所需颜色的列表，以及一个从 1 到 8 的数字，用于表示...
What is the fastest way to get the value of π?
...ically, I'm using ways that don't involve using #define constants like M_PI , or hard-coding the number in.
22 Answers
...
Is there a Python caching library?
...
From Python 3.2 you can use the decorator @lru_cache from the functools library.
It's a Last Recently Used cache, so there is no expiration time for the items in it, but as a fast hack it's very useful.
from functools import lru_cache
@lru_cache(maxsize=256)
def f(x):
...
Getting the class name of an instance?
...
Have you tried the __name__ attribute of the class? ie type(x).__name__ will give you the name of the class, which I think is what you want.
>>> import itertools
>>> x = itertools.count(0)
>>> type(x).__name__
'count...
Explaining Python's '__enter__' and '__exit__'
...
Using these magic methods (__enter__, __exit__) allows you to implement objects which can be used easily with the with statement.
The idea is that it makes it easy to build code which needs some 'cleandown' code executed (think of it as a try-finally...