    sorted(range(len(a)), key=lambda i: a[i])[-2:]

or

    sorted(range(len(a)), key=lambda i: a[i], reverse=True)[:2]

or

    import operator

    zip(*sorted(enumerate(a), key=operator.itemgetter(1)))[0][-2:]

or (for long lists), consider using [`heapq.nlargest`](https://docs.python.org/library/heapq.html#heapq.nlargest)

    zip(*heapq.nlargest(2, enumerate(a), key=operator.itemgetter(1)))[0]

Just a NumPy alternative:

    import numpy as np

    top_2_idx = np.argsort(a)[-2:]
    top_2_values = [a[i] for i in top_2_idx]



Under what conditions does [ContentResolver.query][1]() return null instead of a cursor object?  I&#39;ve gotten empty cursors before but just realized that the method can also return null.  I haven&#39;t been able to trace the circumstances that this happens in, though.


  [1]: http://developer.android.com/reference/android/content/ContentResolver.html

What causes Android&#39;s ContentResolver.query() to return null?

In the Activity I have :

    public class tabsmain extends Activity{
    	public static Context appContext;
    	
    	public boolean lf_ch=false;
    		
    	public void onCreate(Bundle savedInstanceState){

I would like to access and possibly change lf_ch from a fragment inside tabsmain;

    public class tabquests extends Fragment{ 
    	public CheckBox lc;
    @Override
    	public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)//onCreateView
    	{ 
    lc.setChecked(//set it to lf_ch);



However, I can&#39;t seem to access the value of lf_ch.



How to access Activity Variables from a fragment Android

I have a list say `a = [5,3,1,4,10]`. I need to get indices of the top two values of the list, that is for `5` and `10` I would get `[0, 4]`. Is there a one-liner that Python offers for such a case?

Get indices of the top N values of a list

<p>I have a list say <code>a = [5,3,1,4,10]</code>. I need to get indices of the top two values of the list, that is for <code>5</code> and <code>10</code> I would get <code>[0, 4]</code>. Is there a one-liner that Python offers for such a case?</p>


I&#39;m trying to write tests for a class that has methods like:

    import datetime
    import pytz
    
    class MyClass:
        def get_now(self, timezone):
            return datetime.datetime.now(timezone)
    
        def do_many_things(self, tz_string=&#39;Europe/London&#39;):
            tz = pytz.timezone(tz_string)
            localtime_now = self.get_now(tz)
            ...
            return things

I want to test it, and to do so I need to make sure that the `datetime.datetime.now()` call returns something predictable.

I&#39;ve been reading lots of examples of using [Mock](http://www.voidspace.org.uk/python/mock/) in tests, but haven&#39;t found anything quite like what I need, and I can&#39;t work out how to use it in my tests.

I separated the `get_now()` method out in case it&#39;s easier to mock that, instead of `datetime.datetime.now()`, but I&#39;m still stumped. Any thoughts on how to write UnitTests for this using Mock? (This is all in Django, fwiw; I&#39;m not sure if this makes a difference in this case.)


How to mock python&#39;s datetime.now() in a class method for unit testing?

`scipy.spatial.distance.pdist` returns a condensed distance matrix. From [the documentation][1]:

&gt; Returns a condensed distance matrix Y. For each  and  (where ), the metric dist(u=X[i], v=X[j]) is computed and stored in entry ij.

I thought `ij` meant `i*j`. But I think I might be wrong. Consider

&lt;!-- language: lang-py --&gt;

    X = array([[1,2], [1,2], [3,4]])
    dist_matrix = pdist(X)

then the documentation says that `dist(X[0], X[2])` should be `dist_matrix[0*2]`. However, `dist_matrix[0*2]` is 0 -- not 2.8 as it should be. 

What&#39;s the formula I should use to access the similarity of a two vectors, given `i` and `j`?


  [1]: http://docs.scipy.org/doc/scipy/reference/generated/scipy.spatial.distance.pdist.html

How does condensed distance matrix work? (pdist)

I have a function that analyzes a CSV file with Pandas and produces a dict with summary information. I want to return the results as a response from a Flask view. How do I return a JSON response?

    @app.route(&quot;/summary&quot;)
	def summary():
        d = make_summary()
	    # send it back as json

How to return a dict as a JSON response from a Flask view?

Perhaps I&#39;ve fallen victim to misinformation on the web, but I think it&#39;s more likely just that I&#39;ve misunderstood something.  Based on what I&#39;ve learned so far, range() is a generator, and generators can be used as iterators.  However, this code:

    myrange = range(10)
    print(next(myrange))
gives me this error:

    TypeError: &#39;range&#39; object is not an iterator
What am I missing here?  I was expecting this to print 0, and to advance to the next value in `myrange`.  I&#39;m new to Python, so please accept my apologies for the rather basic question, but I couldn&#39;t find a good explanation anywhere else.

If range() is a generator in Python 3.3, why can I not call next() on a range?

I have a string that I got from reading a HTML webpage with bullets that have a symbol like &quot;•&quot; because of the bulleted list. Note that the text is an HTML source from a webpage using Python 2.7&#39;s `urllib2.read(webaddress)`.

I know the unicode character for the bullet character as `U+2022`, but how do I actually replace that unicode character with something else?

I tried doing
`str.replace(&quot;•&quot;, &quot;something&quot;)`

but it does not appear to work... how do I do this?

How to replace unicode characters in string with something else python?

I have a following method...which actually takes the list of sentences and splits each sentence into words. Here is it:

    public List&lt;String&gt; getWords(List&lt;String&gt; strSentences){
   	allWords = new ArrayList&lt;String&gt;();
    	Iterator&lt;String&gt; itrTemp = strSentences.iterator();
    	while(itrTemp.hasNext()){
    		String strTemp = itrTemp.next();
    		allWords = Arrays.asList(strTemp.toLowerCase().split(&quot;\\s+&quot;));    		
    	}
    	return allWords;
    }

I have to pass this list into a hashmap in the following format     
    
    HashMap&lt;String, ArrayList&lt;String&gt;&gt;

so this method returns List and I need an ArrayList? If I try to cast it doesn&#39;t work out... any suggestions?

Also, if I change the ArrayList to List in a HashMap, I get       

    java.lang.UnsupportedOperationException

because of this line in my code 

    sentenceList.add(((Element)sentenceNodeList.item(sentenceIndex)).getTextContent());

Any better suggestions?



List&lt;String&gt; to ArrayList&lt;String&gt; conversion issue

What would be the most efficient way to select all the items in a specific range from a list and put it in a new one?

    List&lt;DataClass&gt; xmlList = new List&lt;DataClass&gt;();

This is my List, and I would like to put all the DataClass items between the range (3 - 7) in a new List&lt;DataClass&gt;.

What would be the most efficient way? A foreach loop that that count++ everytime untill he reaches the items between a the range and add those items to the new list?


How to get items in a specific range (3 - 7) from list?

I have a list with ~10^6 tuples in it like this:

    [(101, 153), (255, 827), (361, 961), ...]
      ^     ^
      X     Y

I want to find the maximum value of the `Y`s in this list, but also want to know the `X` that it is bound to.

How do I do this?

How to find the maximum value in a list of tuples?

There is no `AddRange()` method for `IList&lt;T&gt;`.

How can I add a list of items to an `IList&lt;T&gt;` without iterating through the items and using the `Add()` method?


How to add a range of items to an IList?

Say I have some Python list, `my_list` which contains N elements. Single elements may be indexed by using `my_list[i_1]`, where `i_1` is the index of the desired element. However, Python lists may also be indexed `my_list[i_1:i_2]` where a &quot;slice&quot; of the list from `i_1` to `i_2` is desired. What is the Big-O (worst-case) notation to slice a list of size N?

Personally, if I were coding the &quot;slicer&quot; I would iterate from `i_1` to `i_2`, generate a new list and return it, implying O(N), is this how Python does it?

Thank you,

Content Type	Original Author	Original Content on Stackoverflow
Question	hardikudeshi	View Question on Stackoverflow
Solution 1 - Python	Fred Foo	View Answer on Stackoverflow
Solution 2 - Python	aikramer2	View Answer on Stackoverflow

Get indices of the top N values of a list

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

How to access Activity Variables from a fragment Android

What causes Android's ContentResolver.query() to return null?

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