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In Python, how do I determine if an object is iterable?
...'ve lately started to get more and more annoyed by objects which only have __getitem__ being considered iterable. There are valid reasons to have __getitem__ in a non-iterable object and with them the above code doesn't work well. As a real life example we can use Faker. The above code reports it be...
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...