&gt; This PEP introduces changes intended to help eliminate ambiguities in Python&#39;s grammar, simplify exception classes, simplify garbage collection for exceptions and reduce the size of the language in Python 3.0.

&lt;a href=&quot;http://www.python.org/dev/peps/pep-3110/&quot;&gt;PEP 3110: &quot;Catching Exceptions in Python 3000&quot;&lt;/a&gt;

Short answer for the why: `Exception, e` and `Exception, TypeError` are hard to tell apart. Long answer: what Ignacio said.

The first proposal for using the &quot;as&quot; is here: http://mail.python.org/pipermail/python-dev/2006-March/062449.html.
They thought it would be more intuitive to read the code

I&#39;m printing text to a canvas in a pretty straight forward way:

    var ctx = canvas.getContext(&#39;2d&#39;);
    ctx.font = &quot;10pt Courier&quot;;
    ctx.fillText(&quot;Hello World&quot;, 100, 100);

But how can I change the text to bold, italic or both? Any suggestions to fix that simple example?

How do I style HTML5 canvas text to be bold and/or italic?

How would I determine whether the element returned by an :input filter in jQuery is a textbox or select list?

I want to have a different behavior for each ( textbox returns text value, select returns both key and text)


Example setup:

    &lt;div id=&quot;InputBody&quot;&gt;
	&lt;div class=&quot;box&quot;&gt;
		&lt;span id=&quot;StartDate&quot;&gt;
			&lt;input type=&quot;text&quot; id=&quot;control1&quot;&gt;
		&lt;/span&gt;
		&lt;span id=&quot;Result&quot;&gt;
			&lt;input type=&quot;text&quot; id=&quot;control2&quot;&gt;
		&lt;/span&gt;
		&lt;span id=&quot;SelectList&quot;&gt;
			&lt;select&gt;
				&lt;option value=&quot;1&quot;&gt;Option 1&lt;/option&gt;
				&lt;option value=&quot;2&quot;&gt;Option 2&lt;/option&gt;
				&lt;option value=&quot;3&quot;&gt;Option 3&lt;/option&gt;
			&lt;/select&gt;
		&lt;/span&gt;
	&lt;/div&gt;
	&lt;div class=&quot;box&quot;&gt;
		&lt;span id=&quot;StartDate&quot;&gt;
			&lt;input type=&quot;text&quot; id=&quot;control1&quot;&gt;
		&lt;/span&gt;
		&lt;span id=&quot;Result&quot;&gt;
			&lt;input type=&quot;text&quot; id=&quot;control2&quot;&gt;
		&lt;/span&gt;
		&lt;span id=&quot;SelectList&quot;&gt;
			&lt;select&gt;
				&lt;option value=&quot;1&quot;&gt;Option 1&lt;/option&gt;
				&lt;option value=&quot;2&quot;&gt;Option 2&lt;/option&gt;
				&lt;option value=&quot;3&quot;&gt;Option 3&lt;/option&gt;
			&lt;/select&gt;
		&lt;/span&gt;
	&lt;/div&gt;
&lt;/div&gt;

and then the script:

    $(&#39;#InputBody&#39;)
        // find all div containers with class = &quot;box&quot;
        .find(&#39;.box&#39;)
        .each(function () {
            console.log(&quot;child: &quot; + this.id);

            // find all spans within the div who have an id attribute set (represents controls we want to capture)
            $(this).find(&#39;span[id]&#39;)
            .each(function () {
                console.log(&quot;span: &quot; + this.id);

                var ctrl = $(this).find(&#39;:input:visible:first&#39;);

                console.log(this.id + &quot; = &quot; + ctrl.val());
                console.log(this.id + &quot; SelectedText = &quot; + ctrl.find(&#39;:selected&#39;).text());

            });

 

jQuery - determine if input element is textbox or select list

In python, there are two ways to catch an exception 


    except Exception, e:

    except Exception as e:

It seems like &#39;as e&#39; is the one to use going forward.  In what version of python did this change?  Any idea why?






In Python, what&#39;s the difference between &#39;except Exception as e&#39; and &#39;except Exception, e&#39;

In python, there are two ways to catch an exception
<pre><code class="hljs language-php">except Exception, e:

except Exception as e:
</code></pre>
It seems like 'as e' is the one to use going forward. In what version of python did this change? Any idea why?

I&#39;d like to get [PyYAML](http://pyyaml.org/)&#39;s loader to load mappings (and ordered mappings) into the Python 2.7+ [OrderedDict](http://docs.python.org/library/collections.html#collections.OrderedDict) type, instead of the vanilla `dict` and the list of pairs it currently uses.

What&#39;s the best way to do that?

In Python, how can you load YAML mappings as OrderedDicts?

Often I find myself wanting to get the first object from a queryset in Django, or return `None` if there aren&#39;t any.  There are lots of ways to do this which all work.  But I&#39;m wondering which is the most performant.

    qs = MyModel.objects.filter(blah = blah)
    if qs.count() &gt; 0:
        return qs[0]
    else:
        return None

Does this result in two database calls?  That seems wasteful.  Is this any faster? 

    qs = MyModel.objects.filter(blah = blah)
    if len(qs) &gt; 0:
        return qs[0]
    else:
        return None

Another option would be:

    qs = MyModel.objects.filter(blah = blah)
    try:
        return qs[0]
    except IndexError:
        return None

This generates a single database call, which is good.  But requires creating an exception object a lot of the time, which is a very memory-intensive thing to do when all you really need is a trivial if-test.

How can I do this with just a single database call and without churning memory with exception objects?


Fastest way to get the first object from a queryset in django?

I have a 2D numpy array. Some of the values in this array are `NaN`. I want to perform certain operations using this array. For example consider the array:

    [[   0.   43.   67.    0.   38.]
     [ 100.   86.   96.  100.   94.]
     [  76.   79.   83.   89.   56.]
     [  88.   NaN   67.   89.   81.]
     [  94.   79.   67.   89.   69.]
     [  88.   79.   58.   72.   63.]
     [  76.   79.   71.   67.   56.]
     [  71.   71.   NaN   56.  100.]]

I am trying to take each row, one at a time, sort it in reversed order to get max 3 values from the row and take their average. The code I tried is:

    # nparr is a 2D numpy array
    for entry in nparr:
        sortedentry = sorted(entry, reverse=True)
        highest_3_values = sortedentry[:3]
        avg_highest_3 = float(sum(highest_3_values)) / 3

This does not work for rows containing `NaN`. My question is, is there a quick way to convert all `NaN` values to zero in the 2D numpy array so that I have no problems with sorting and other things I am trying to do.


convert nan value to zero

I&#39;m curious if there&#39;s a reasonable way to use the (amazing) django-debug-toolbar with AJAX queries. 

For example, I use a jQuery $.get with a bunch of parameters to hit a Django URL and load it inline. If I have an error with that, it isn&#39;t registered on the toolbar. I also can&#39;t use it by copying the AJAX URL because DDT attaches to the body tag of the response, and it wouldn&#39;t make any sense to be including body tags with AJAX responses.

Any direction would be helpful! Thanks!

How to use django-debug-toolbar on AJAX calls?

Why doesn&#39;t list have a safe &quot;get&quot; method like dictionary?

    &gt;&gt;&gt; d = {&#39;a&#39;:&#39;b&#39;}
    &gt;&gt;&gt; d[&#39;a&#39;]
    &#39;b&#39;
    &gt;&gt;&gt; d[&#39;c&#39;]
    KeyError: &#39;c&#39;
    &gt;&gt;&gt; d.get(&#39;c&#39;, &#39;fail&#39;)
    &#39;fail&#39;

    &gt;&gt;&gt; l = [1]
    &gt;&gt;&gt; l[10]
    IndexError: list index out of range

Why doesn&#39;t list have safe &quot;get&quot; method like dictionary?

Google&#39;s [C++ style guide](https://google.github.io/styleguide/cppguide.html#Exceptions) says &quot;We do not use exceptions&quot;. The style does not mention STL with respect to usage of exception. Since STL allocators can fail, how do they handle exceptions thrown by containers?

 1. If they use STL, how is the caller informed of allocation failures? STL methods like `push_back()` or map `operator[]` do not return any status codes.
 2. If they do not use STL, what container implementation do they use?



Google C++ style guide&#39;s No-exceptions rule; STL?

I am printing Python exception messages to a log file with `logging.error`:

    import logging
    try:
        1/0
    except ZeroDivisionError as e:
        logging.error(e)  # ERROR:root:division by zero

Is it possible to print more detailed information about the exception and the code that generated it than just the exception string? Things like line numbers or stack traces would be great.

How do I log a Python error with debug information?

These days, I have been reading a lot the [C++ F.A.Q][1] and especially [this page][2].

Reading through the section I discovered a &quot;technique&quot; that the author calls &quot;exception dispatcher&quot; that allows someone to group all his exception handling in one handy function:

    void handleException()
    {
      try {
        throw; // ?!
      }
      catch (MyException&amp; e) {
        //...code to handle MyException...
      }
      catch (YourException&amp; e) {
        //...code to handle YourException...
      }
    }
     
    void f()
    {
      try {
        //...something that might throw...
      }
      catch (...) {
        handleException();
      }
    }

What bothers me is the single `throw;` statement: if you consider the given example then sure, it is obvious what it does: it rethrows the exception first caught in `f()` and deals with it again.

But what if I call `handleException()` on its own, directly, without doing it from a `catch()` clause ? Is there any specified behavior ?

Additionally for bonus points, is there any other &quot;weird&quot; (probably not the good word) use of `throw` that you know of ?

Thank you.


  [1]: http://www.parashift.com/c++-faq-lite/
  [2]: http://www.parashift.com/c++-faq-lite/exceptions.html

What does a single &quot;throw;&quot; statement do?

I wish to throw an exception and have the following:

    (throw &quot;Some text&quot;)

However it seems to be ignored.

Content Type	Original Author	Original Content on Stackoverflow
Question	Nathan	View Question on Stackoverflow
Solution 1 - Python	Ignacio Vazquez-Abrams	View Answer on Stackoverflow
Solution 2 - Python	nmichaels	View Answer on Stackoverflow
Solution 3 - Python	Fábio Diniz	View Answer on Stackoverflow

In Python, what's the difference between 'except Exception as e' and 'except Exception, e'

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

Solution 3 - Python

jQuery - determine if input element is textbox or select list

How do I style HTML5 canvas text to be bold and/or italic?

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