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Is it possible to make a decorator that makes attributes lazy that do not eval when you try to access it with hasattr() ? I worked out how to make it lazy, but hasattr() makes it evaluate prematurely. E.g.,
class lazyattribute: # Magic. class A: @lazyattribute...
Started by Tim Dumol on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
If you post the code for your lazyattribute magic hopefully someone can suggest an alternative way of testing the presence ... .
The problem is that hasattr uses getattr so your attribute is always going to be evaluated when you use hasattr .
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For code:
class a(object): a='aaa' b=a() print hasattr(a,'a') print hasattr(b,'a')
who can be called by hasattr except 'class somebody'?
Thanks!
Started by zjm1126 on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
Accordingly....
You can call hasattr with any object as the first argument (and any string as the second argument of course includes possibly inheriting or synthesizing it; hasattr(x,'y') is True if and only and catches the exception if any).
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If hasattr(obj, 'attribute'): # do somthing
vs
try: # access obj.attribute except AttributeError, e: # deal with AttributeError
Which should be preferred and why?
Started by Imran on
, 9 posts
by 9 people.
Answer Snippets (Read the full thread at stackoverflow):
hasattr internally and rapidly attribute you're testing, I'd say....
Exceptions should be exceptional.
Shorter is better.
Loop $ python -mtimeit -s 'class C(object): a = 4 c = C()' 'hasattr(c, "a")' 1 loops, best of 3: 0.446The first.
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Ask your Facebook Friends
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Is there a nicer way of doing the following:
try: a.method1() except AttributeError: try: a.method2() except AttributeError: try: a.method3() except AttributeError: raise
It looks pretty nasty and I'd rather not do:
if hasattr(a, 'method1'): a.method1...
Started by Dan on
, 5 posts
by 5 people.
Answer Snippets (Read the full thread at stackoverflow):
Args): for attr in attrs_list: if hasattr(obj, attr): bound_method = getattr(obj, attr) return bound.
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I'm trying to understand if the following Python function:
def factorial(i): if not hasattr(factorial, 'lstFactorial'): factorial.lstFactorial = [None] * 1000 if factorial.lstFactorial[i] is None: iProduct = 1 for iFactor in xrange(1, i+1): iProduct *...
Started by Guy on
, 7 posts
by 7 people.
Answer Snippets (Read the full thread at stackoverflow):
It will return the same results, but the Python version will probably have better performance, because it memoizes the results
Even without knowing Python, it must be clear recursion, whereas the Python ....
Is for caching results.
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I'm trying to do this in scons
ignorefiles = {'EvilFile.c' : 1}; sourcefiles_raw = env.Glob('*.c'); sourcefiles = [x for x in sourcefiles_raw if (hasattr(x, 'name') and x.name not in ignorefiles)];
For some reason the scons Glob() function returns an ...
Started by Jason S on
, 5 posts
by 5 people.
Answer Snippets (Read the full thread at stackoverflow):
Not in ignorefiles]
At least in Python 2.X:
>>> hasattr(None, "name") False
None correctly does not have in sourcefiles_raw if hasattr(x, 'name')] sourcefiles = [x for x in sourcefiles_tmp if x.name.
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I regularly want to check if an object has a member or not. An example is the creation of a singleton in a function. For that purpose, you can use hasattr like this:
class Foo(object): @classmethod def singleton(self): if not hasattr(self, 'instance')...
Started by PierreBdR on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
): @classmethod def singleton(self): if not hasattr(self, 'instance'): self.instance = Foo() return" method is as effective, and mostly, very clean in python, for example:
class Borg: __shared_state.
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Hello,
I am trying to verify the that target exposes a https web service. I have code to connect via HTTP but I am not sure how to connect via HTTPS. I have read you use SSL but I have also read that it did not support certificate errors. The code I have...
Started by chrissygormley on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
#!/usr/bin/env python import httplib c = httplib.HTTPSConnection("ccc.de')
To check for ssl support in Python 2.6+ :
try: import ssl except ImportError: print "error: no ssl IOError, e: if hasattr(....
Was compiled with SSL support.
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I have an object of class 'D' in python, and I want to sequentially execute the 'run' method as defined by 'D' and each of it's ancestors ('A', 'B' and 'C').
I'm able to accomplish this like this
class A(object): def run_all(self): # I prefer to execute...
Started by russell_h on
, 4 posts
by 4 people.
Answer Snippets (Read the full thread at stackoverflow):
Unfortunately, in Python check on hasattr is quite....
From Python documentation" there's no further superclass to go up to ( object does not define a run method).
This kind of scenario in mind, and I would use it without any hesitation .
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I wrote code like this
>>> class a(object): def __init__(self): self.__call__ = lambda x:x >>> b = a()
I expected that object of class a should be callable object but eventually it is not.
>>> b() Traceback (most recent call...
Started by kjshim on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
In this, which is why we're all better off with the new-style ones -- which are the only ones left in Python.
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