Use [`argsort`](https://numpy.org/doc/stable/reference/generated/numpy.argsort.html) as follows:

    arr1inds = arr1.argsort()
    sorted_arr1 = arr1[arr1inds[::-1]]
    sorted_arr2 = arr2[arr1inds[::-1]]

This example sorts in descending order.

Use the zip function: `zip( *sorted( zip(arr1, arr2) ) )`  This will do what you need.  

Now the explanation:
`zip(arr1, arr2)` will combine the two lists, so you&#39;ve got [(0, [...list 0...]), (1, [...list 1...]), ...]
Next we run `sorted(...)`, which by default sorts based on the first field in the tuple.
Then we run `zip(...)` again, which takes the tuples from sorted, and creates two lists, from the first element in the tuple (from arr1) and the second element (from arr2). 

I have renamed a python class that is part of a library. I am willing to leave a possibility to use its previous name for some time but would like to warn user that it&#39;s deprecated and will be removed in the future.

I think that to provide backward compatibility it will be enough to use an alias like that:

    class NewClsName:
        pass

    OldClsName = NewClsName

I have no idea how to mark the `OldClsName` as deprecated in an elegant way. Maybe I could make `OldClsName` a function which emits a warning (to logs) and constructs the `NewClsName` object from its parameters (using `*args` and `**kvargs`) but it doesn&#39;t seem elegant enough (or maybe it is?).

However, I don&#39;t know how Python standard library deprecation warnings work. I imagine that there may be some nice magic to deal with deprecation, e.g. allowing treating it as errors or silencing depending on some interpreter&#39;s command line option.

The question is: How to warn users about using an obsolete class alias (or obsolete class in general).

**EDIT**: The function approach doesn&#39;t work for me (I already gave it a try) because the class has some class methods (factory methods) which can&#39;t be called when the `OldClsName` is defined as a function. Following code won&#39;t work:

    class NewClsName(object):
        @classmethod
        def CreateVariant1( cls, ... ):
            pass

        @classmethod
        def CreateVariant2( cls, ... ):
            pass

    def OldClsName(*args, **kwargs):
        warnings.warn(&quot;The &#39;OldClsName&#39; class was renamed [...]&quot;,
                      DeprecationWarning )
        return NewClsName(*args, **kwargs)

    OldClsName.CreateVariant1( ... )

Because of:

    AttributeError: &#39;function&#39; object has no attribute &#39;CreateVariant1&#39;

Is inheritance my only option? To be honest, it doesn&#39;t look very clean to me - it affects class hierarchy through introduction of unnecessary derivation. Additionally, `OldClsName is not NewClsName` what is not an issue in most cases but may be a problem in case of poorly written code using the library.

I could also create a dummy, unrelated `OldClsName` class and implement a constructor as well as wrappers for all class methods in it, but it is even worse solution, in my opinion.

How to warn about class (name) deprecation

How can you create an md5 hash for a string on a mac using `bash`?  `md5sum` does not exist in my environment. I did a `man` for md5 but I&#39;m confused about what that really does.

    md5 &quot;string&quot;

does not return a hash.

How to create md5 hash in bash in Mac OS X

I&#39;m trying to sort the rows of one array by the values of another.  For example:

    import numpy as np
    arr1 = np.random.normal(1, 1, 80)
    arr2 = np.random.normal(1,1, (80,100))

I want to sort `arr1` in descending order, and to have the current relationship between `arr1` and `arr2` to be maintained (ie, after sorting both, the rows of `arr1[0]` and `arr2[0, :]` are the same).

Sort array&#39;s rows by another array in Python

I'm trying to sort the rows of one array by the values of another. For example:
<pre><code class="hljs language-ini">import numpy as np
arr1 = np.random.normal(1, 1, 80)
arr2 = np.random.normal(1,1, (80,100))
</code></pre>
I want to sort <code>arr1</code> in descending order, and to have the current relationship between <code>arr1</code> and <code>arr2</code> to be maintained (ie, after sorting both, the rows of <code>arr1[0]</code> and <code>arr2[0, :]</code> are the same).

I am trying to understand the Python `hash` function under the hood. I created a custom class where all instances return the same hash value. 

    class C:
        def __hash__(self):
            return 42

I just assumed that only one instance of the above class can be in a `dict` at any time, but in fact a `dict` can have multiple elements with the same hash.

    c, d = C(), C()
    x = {c: &#39;c&#39;, d: &#39;d&#39;}
    print(x)
    # {&lt;__main__.C object at 0x7f0824087b80&gt;: &#39;c&#39;, &lt;__main__.C object at 0x7f0823ae2d60&gt;: &#39;d&#39;}
    # note that the dict has 2 elements

I experimented a little more and found that if I override the `__eq__` method such that all the instances of the class compare equal, then the `dict` only allows one instance.

    class D:
        def __hash__(self):
            return 42
        def __eq__(self, other):
            return True

    p, q = D(), D()
    y = {p: &#39;p&#39;, q: &#39;q&#39;}
    print(y)
    # {&lt;__main__.D object at 0x7f0823a9af40&gt;: &#39;q&#39;}
    # note that the dict only has 1 element

So I am curious to know how a `dict` can have multiple elements with the same hash.

Why can a Python dict have multiple keys with the same hash?

I have a regular expression like this:

    regexp = u&#39;ba[r|z|d]&#39;

Function must return True if word contains __bar__, __baz__ or __bad__.
In short, I need regexp analog for Python&#39;s

    &#39;any-string&#39; in &#39;text&#39;

How can I realize it? Thanks!

python&#39;s re: return True if string contains regex pattern

I am trying to save plots I make using matplotlib; however, the images are saving blank.

Here is my code:

    plt.subplot(121)
    plt.imshow(dataStack, cmap=mpl.cm.bone)
    
    plt.subplot(122)
    y = copy.deepcopy(tumorStack)
    y = np.ma.masked_where(y == 0, y)
   
    plt.imshow(dataStack, cmap=mpl.cm.bone)
    plt.imshow(y, cmap=mpl.cm.jet_r, interpolation=&#39;nearest&#39;)
    
    if T0 is not None:
        plt.subplot(123)
        plt.imshow(T0, cmap=mpl.cm.bone)
        
        #plt.subplot(124)
        #Autozoom
        
    #else:
        #plt.subplot(124)
        #Autozoom
    
    plt.show()
    plt.draw()
    plt.savefig(&#39;tessstttyyy.png&#39;, dpi=100)

And tessstttyyy.png is blank (also tried with .jpg)

Matplotlib (pyplot) savefig outputs blank image

I&#39;m running a suite of tests (.py files) using nosetests.  Using a classic

    import pdb; pdb.set_trace()

the nosetests run just never completes.  It just hangs right where the breakpoint has been set, but never drops into the pdb debugger.

Any ideas why this would be?  I&#39;ve tried moving the breakpoint to a number of different positions (other test functions, other files) to no avail.



pdb.set_trace() causing frozen nosetests, does not drop into debugger

From a text file containing three columns of data I want to be able to just take a `slice` of data from all three columns where the values in the first column are equal to the values defined in `above`. I then want to put the slice of data into a new array called `slice` (I am using **Python 2.7**)

    above = range(18000, 18060, 5)

    data = np.loadtxt(open(&#39;data.txt&#39;), delimiter=None)

    energies = (np.hsplit(data, 3))[0]

    slice = set(energies)&amp;set(above)

The above comes back with:

    Traceback (most recent call last):
      File &quot;&lt;pyshell#27&gt;&quot;, line 1, in &lt;module&gt;
        set(energies)&amp;set(above)
    TypeError: unhashable type: &#39;numpy.ndarray


TypeError: unhashable type: &#39;numpy.ndarray&#39;

While reading up on numpy, I encountered the function [`numpy.histogram()`][1].

What is it for and **how does it work?** In the docs they mention **bins**: What are they?

Some googling led me to the [definition of Histograms in general][2]. I get that. But unfortunately I can&#39;t link this knowledge to the examples given in the docs.


  [1]: http://docs.scipy.org/doc/numpy/reference/generated/numpy.histogram.html
  [2]: http://en.wikipedia.org/wiki/Histogram

How does numpy.histogram() work?

I have a list of 3-tuples representing a set of points in 3D space. I want to plot a surface that covers all these points.

The `plot_surface` function in the `mplot3d` package requires as arguments X,Y and Z to be 2d arrays. Is `plot_surface` the right function to plot surface and how do I transform my data into the required format?

    data = [(x1,y1,z1),(x2,y2,z2),.....,(xn,yn,zn)]

surface plots in matplotlib

In keeping with the &quot;There&#39;s only one obvious way to do it&quot;, how do you get the magnitude of a vector (1D array) in Numpy?

    def mag(x): 
        return math.sqrt(sum(i**2 for i in x))

The above works, but I *cannot believe* that I must specify such a trivial and core function myself.

How do you get the magnitude of a vector in Numpy?

I have two simple one-dimensional arrays in [NumPy][1]. I should be able to concatenate them using [numpy.concatenate][2]. But I get this error for the code below:

&gt; TypeError: only length-1 arrays can be converted to Python scalars


### Code

    import numpy
    a = numpy.array([1, 2, 3])
    b = numpy.array([5, 6])
    numpy.concatenate(a, b)

Why?

  [1]: http://en.wikipedia.org/wiki/NumPy
  [2]: http://docs.scipy.org/doc/numpy/reference/generated/numpy.concatenate.html


Concatenating two one-dimensional NumPy arrays

Should I use

    std::sort(numbers.begin(), numbers.end(), std::greater&lt;int&gt;());

or

    std::sort(numbers.rbegin(), numbers.rend());   // note: reverse iterators

to sort a vector in descending order? Are there any benefits or drawbacks with one approach or the other?

Sorting a vector in descending order

If i have a string is there a built in function to sort the characters or would I have to write my own?

for example:

    string word = &quot;dabc&quot;;

I would want to change it so that:

    string sortedWord = &quot;abcd&quot;;

Maybe using char is a better option? How would I do this in C++?

Sorting Characters Of A C++ String

We have two columns in a `DataTable`, like so:

    COL1   COL2
    Abc    5
    Def	   8
    Ghi	   3


We&#39;re trying to sort this `datatable` based on `COL2` in decreasing order. 

    COL1            COL2
    ghi             8
    abc             4
    def             3
    jkl             1

We tried this:
    
    ft.DefaultView.Sort = &quot;COL2 desc&quot;;
    ft = ft.DefaultView.ToTable(true);

but, without using a `DataView`, we want to sort the `DataTable` itself, not the `DataView`.




Sorting rows in a data table

Im trying to sort through an arraylist of objects by a particular value within the object. What would be the best approach to do such a thing. Should I use Collections.sort() with some kind of comparator? 

Im trying to sort a list of objects by a float value they hold in one of the variables.


EDIT:
This is what I have so far:

    public class CustomComparator implements Comparator&lt;Marker&gt; {
	    @Override
	    public int compare(Mark o1, Mark o2) {
	        return o1.getDistance().compareTo(o2.getDistance());
	    }
	}

the error states: Cannot invoke compareTo(double) on the primitive type double.

Is it because a comparator cant return anything other than a certain type?


Android-java- How to sort a list of objects by a certain value within the object

I have an array of objects to sort. Each object has two parameters: Strength and Name

    objects = []
    object[0] = {strength: 3, name: &quot;Leo&quot;}
    object[1] = {strength: 3, name: &quot;Mike&quot;}

I want to sort first by Strength and then by name alphabetically. I am using the following code to sort by the first parameter. How do I sort then by the second? 
    

    function sortF(ob1,ob2) {
      if (ob1.strength &gt; ob2.strength) {return 1}
	  else if (ob1.strength &lt; ob2.strength){return -1}
	  return 0;
	};

Thanks for your help.

(I am using [Array.sort()][1] with the aforementioned sortF as the sort comparison function passed into it.)


  [1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort

Content Type	Original Author	Original Content on Stackoverflow
Question	mike	View Question on Stackoverflow
Solution 1 - Python	keflavich	View Answer on Stackoverflow
Solution 2 - Python	mklauber	View Answer on Stackoverflow

Sort array's rows by another array in Python

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How to create md5 hash in bash in Mac OS X

How to warn about class (name) deprecation

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