A more direct analogue to `dict.get(key, default)` than `hasattr` is `getattr`.

    val = getattr(obj, &#39;attr_to_check&#39;, default_value)

(Where `default_value` is optional, raising an exception on no attribute if not found.)

For your example, you would pass `False`.

Do you mean `hasattr()` perhaps?

    hasattr(object, &quot;attribute name&quot;) #Returns True or False

[Python.org doc - Built in functions - hasattr()][1]


  [1]: http://docs.python.org/library/functions.html#hasattr


You can also do this, which is a bit more cluttered and doesn&#39;t work for methods.

    &quot;attribute&quot; in obj.__dict__

For checking if a key is in a dictionary you can use `in`: `&#39;key&#39; in dictionary`.

For checking for attributes in object use the `hasattr()` function: `hasattr(obj, &#39;attribute&#39;)`

As Knuth said,

&gt;We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil.

This is something which often comes up in Stack Overflow answers to questions like &quot;which is the most efficient loop mechanism&quot;, &quot;SQL optimisation techniques?&quot; ([and so on](http://www.google.com/search?q=site%3Astackoverflow.com+%22premature+optimization%22)). The standard answer to these optimisation-tips questions is to profile your code and see if it&#39;s a problem first, and if it&#39;s not, then therefore your new technique is unneeded.

My question is, if a particular technique is different but not particularly obscure or obfuscated, can that really be considered a premature optimisation?

Here&#39;s a related article by Randall Hyde called *[The Fallacy of Premature Optimization](http://ubiquity.acm.org/article.cfm?id=1513451)*.

When is optimisation premature?

I&#39;m looking for an algorithm to generate permutations of a set in such a way that I could make a lazy list of them in Clojure.  i.e. I&#39;d like to iterate over a list of permutations where each permutation is not calculated until I request it, and all of the permutations don&#39;t have to be stored in memory at once.

Alternatively I&#39;m looking for an algorithm where given a certain set, it will return the &quot;next&quot; permutation of that set, in such a way that repeatedly calling the function on its own output will cycle through all permutations of the original set, in some order (what the order is doesn&#39;t matter).

Is there such an algorithm?  Most of the permutation-generating algorithms I&#39;ve seen tend to generate them all at once (usually recursively), which doesn&#39;t scale to very large sets.  An implementation in Clojure (or another functional language) would be helpful but I can figure it out from pseudocode.

Generating permutations lazily

If I had a dictionary `dict` and I wanted to check for `dict[&#39;key&#39;]` I could either do so in a `try` block (bleh!) or use the `get()` method, with `False` as a default value.

I&#39;d like to do the same thing for `object.attribute`. That is, I already have object to return `False` if it hasn&#39;t been set, but then that gives me errors like

&gt; AttributeError: &#39;bool&#39; object has no attribute &#39;attribute&#39;

A get() like method for checking for Python attributes

If I had a dictionary <code>dict</code> and I wanted to check for <code>dict['key']</code> I could either do so in a <code>try</code> block (bleh!) or use the <code>get()</code> method, with <code>False</code> as a default value.
I'd like to do the same thing for <code>object.attribute</code>. That is, I already have object to return <code>False</code> if it hasn't been set, but then that gives me errors like
> AttributeError: 'bool' object has no attribute 'attribute'


  In python do you generally use [PEP 8 -- Style Guide for Python Code][1] as your coding standards/guidelines?  Are there any other formalized standards that you prefer?

  [1]: http://www.python.org/dev/peps/pep-0008/

Python coding standards/best practices

I am interested in enabling code folding in Vim for Python code. I have noticed multiple ways to do so.

Does anyone have a preferred way to do Python code folding in Vim? I.e, 

  - Do you have a particular Vim plugin that you use and like?
  - Do you use manual folding or do you place markers in comments?
  - Any other recommended ways to do code folding for Python in Vim?





What is the recommended way to use Vim folding for Python code

this is my log output

    INFO main digestemails - process inbox
    INFO main digestemails - checking for emails in c:\development\DCMail\email\KN-Source
    INFO main digestemails - digesting 003d01c95a7b_3446880_0202fea9@xxxx.com.eml
    INFO main digestemails - extracting attachments
    INFO main digestemails - no attachments or no attachments supported
    INFO main digestemails - updating database
    INFO main digestemails - email -&gt; COMPLETED folder
    INFO main digestemails -  

I would like a time stamp per log message ie

    INFO 2008-12-25 13:14:00 digestemails - email -&gt; COMPLETED folder

here is my log4j config file


    log4j.rootLogger=debug, stdout, R

    log4j.appender.stdout=org.apache.log4j.ConsoleAppender
    log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

    # Pattern to output the caller&#39;s file name and line number.
    log4j.appender.stdout.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n

    log4j.appender.R=org.apache.log4j.RollingFileAppender
    log4j.appender.R.File=c:\\development\\DCMail\\logs\\digestlogfolder\\digest-logfile.log

    log4j.appender.R.MaxFileSize=100KB
    # Keep one backup file
    log4j.appender.R.MaxBackupIndex=1

    log4j.appender.R.layout=org.apache.log4j.PatternLayout
    log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n 

How do I do it?

log4j with timestamp per log entry

I&#39;m trying to get started with unit testing in Python and I was wondering if someone could explain the advantages and disadvantages of doctest and unittest.  

What conditions would you use each for?

Python - doctest vs. unittest

I&#39;m calling a bunch of methods that return a list.  The list may be empty.  If the list is non-empty, I want to return the first item; otherwise, I want to return `None`.  This code works:

```py
def main():
    my_list = get_list()
    if len(my_list) &gt; 0:
        return my_list[0]
    return None
```

but it seems to me that there should be a simple one-line idiom for doing this. Is there?

Python idiom to return first item or None

I am looking for a way to localize properties names displayed in a PropertyGrid. The property&#39;s name may be &quot;overriden&quot; using the DisplayNameAttribute attribute. Unfortunately attributes can not have non constant expressions. So I can not use strongly typed resources such as: 

    class Foo
    {
       [DisplayAttribute(Resources.MyPropertyNameLocalized)]  // do not compile
       string MyProperty {get; set;}
    }

I had a look around and found some suggestion to inherit from DisplayNameAttribute to be able to use resource. I would end up up with code like: 

    class Foo
    {
       [MyLocalizedDisplayAttribute(&quot;MyPropertyNameLocalized&quot;)] // not strongly typed
       string MyProperty {get; set;}
    }

However I lose strongly typed resource benefits which is definitely not a good thing. Then I came across [DisplayNameResourceAttribute][1] which may be what I&#39;m looking for. But it&#39;s supposed to be in Microsoft.VisualStudio.Modeling.Design namespace and I can&#39;t find what reference I am supposed to add for this namespace.

Anybody know if there&#39;s a easier way to achieve DisplayName localization in a good way ? or if there is as way to use what Microsoft seems to be using for Visual Studio ?


  [1]: http://msdn.microsoft.com/en-us/library/microsoft.visualstudio.modeling.design.displaynameresourceattribute.aspx

Localization of DisplayNameAttribute

Is there an attribute I can use on a method so that when stepping through some code in Debug mode the Debugger stays on the outside of the method?


Attribute to Skip over a Method while Stepping in Debug Mode

I&#39;ve been trying to use decimal values as params for a field attribute but I get a compiler error.

I found this blog post [link][1] saying it wasn&#39;t possible in .NET to use then, does anybody know why they choose this or how can I use decimal params?


  [1]: http://salamakha.com/blog/2007/09/21/decimal-in-c-attributes/

use decimal values as attribute params in c#?

This would appear to imply &quot;no&quot;. Which is unfortunate.

    [AttributeUsage(AttributeTargets.Interface | AttributeTargets.Class,
     AllowMultiple = true, Inherited = true)]
    public class CustomDescriptionAttribute : Attribute
    {
        public string Description { get; private set; }

        public CustomDescriptionAttribute(string description)
        {
            Description = description;
        }
    }

    [CustomDescription(&quot;IProjectController&quot;)]
    public interface IProjectController
    {
        void Create(string projectName);
    }

    internal class ProjectController : IProjectController
    {
        public void Create(string projectName)
        {
        }
    }

    [TestFixture]
    public class CustomDescriptionAttributeTests
    {
        [Test]
        public void ProjectController_ShouldHaveCustomDescriptionAttribute()
        {
            Type type = typeof(ProjectController);
            object[] attributes = type.GetCustomAttributes(
                typeof(CustomDescriptionAttribute),
                true);

            // NUnit.Framework.AssertionException:   Expected: 1   But was:  0
            Assert.AreEqual(1, attributes.Length);
        }
    }

Can a class inherit attributes from an interface? Or am I barking up the wrong tree here?


Can a C# class inherit attributes from its interface?

I&#39;m using a custom attribute inherited from an attribute class. I&#39;m using it like this:

    [MyCustomAttribute(&quot;CONTROL&quot;)]
    [MyCustomAttribute(&quot;ALT&quot;)]
    [MyCustomAttribute(&quot;SHIFT&quot;)]
    [MyCustomAttribute(&quot;D&quot;)]
    public void setColor()
    {
    
    }

But the &quot;Duplicate &#39;MyCustomAttribute&#39; attribute&quot; error is shown.  
How can I create a duplicate allowed attribute?

Content Type	Original Author	Original Content on Stackoverflow
Question	jamtoday	View Question on Stackoverflow
Solution 1 - Python	Brian	View Answer on Stackoverflow
Solution 2 - Python	Zoomulator	View Answer on Stackoverflow
Solution 3 - Python	unbeknown	View Answer on Stackoverflow

A get() like method for checking for Python attributes

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

Solution 3 - Python

Generating permutations lazily

When is optimisation premature?

Attributions