It&#39;s as simple as `cm.hot(0.3)`:
```python
import matplotlib.cm as cm
    
print(cm.hot(0.3))
```
```
(0.8240081481370484, 0.0, 0.0, 1.0)
```
If you also want to have the normalizer, use
```python
import matplotlib as mpl
import matplotlib.cm as cm
   
norm = mpl.colors.Normalize(vmin=-20, vmax=10)
cmap = cm.hot
x = 0.3

m = cm.ScalarMappable(norm=norm, cmap=cmap)
print(m.to_rgba(x))
```
```
(1.0, 0.8225486412996345, 0.0, 1.0)
```

You can get a color from a colormap by supplying an argument between 0 and 1, e.g. `cm.autumn(0.5)`. 

If there is a normalization instance in the game, use the return of the Normalization instead:

    import matplotlib.cm as cm
    from matplotlib.colors import Normalize
    
    cmap = cm.autumn
    norm = Normalize(vmin=-20, vmax=10)
    print cmap(norm(5))

Number value to colormap color
```
import matplotlib.cm as cm
import matplotlib as matplotlib

def color_map_color(value, cmap_name=&#39;Wistia&#39;, vmin=0, vmax=1):
    # norm = plt.Normalize(vmin, vmax)
    norm = matplotlib.colors.Normalize(vmin=vmin, vmax=vmax)
    cmap = cm.get_cmap(cmap_name)  # PiYG
    rgb = cmap(norm(abs(value)))[:3]  # will return rgba, we take only first 3 so we get rgb
    color = matplotlib.colors.rgb2hex(rgb)
    return color
```

I would like to build a method inside a class with default values arguments taken from this class. In general I do filtering on some data. Inside my class I have a method where normally I pass vector of data. Sometimes I don&#39;t have the vector and I take simulated data. Every time I do not pass a particular vector I would like to take simulated data by default. I thought it should be an easy construction where inside my method definition I say `a=self.vector`. But for some reason I have an error `NameError: name &#39;self&#39; is not defined`.  The simplified construction is:

    class baseClass(object):  # This class takes an initial data or simulation
        def __init__(self):
            self.x = 1
            self.y = 2
            
    class extendedClass(baseClass): # This class does some filtering
        def __init__(self):
            baseClass.__init__(self)
            self.z = 5
        def doSomething(self, a=self.z):
            self.z = 3
            self.b = a
        
    if __name__ == &#39;__main__&#39;:
        a = extendedClass()
        print a.__dict__
        a.doSomething()
        print a.__dict__

An output I expected should be:

    {&#39;y&#39;: 2, &#39;x&#39;: 1, &#39;z&#39;: 5}
    {&#39;y&#39;: 2, &#39;x&#39;: 1, &#39;z&#39;: 3, &#39;b&#39;: 5}

I tried default assignment as `def doSomething(self, a=z):` obviously it doesn&#39;t work ever. As far as I understand `self.z` is visible in this scope and should not be a problem to have it as a default value. Don&#39;t know why I have this error and how to do it. This is probably an easy question, but I try to figure it out or find the solution with no lack for sometime already. I found [similar](https://stackoverflow.com/questions/9286533/how-to-use-an-member-variable-as-a-default-argument-c) questions only for other languages.


assigning class variable as default value to class method argument

I&#39;m wondering when should I use `handler.post(runnable);` and when should I use 
`new Thread(runnable).start();`

It is mentioned in developers documentation for Handler:

&gt; Causes the Runnable r to be added to the message queue. The runnable
&gt; will be run on the thread to which this handler is attached.

Does this mean if I write in the `onCreate()` of `Activity` class:

    Handler handler = new Handler();
    handler.post(runnable);

then runnable will be called in a separate thread or in the Activity&#39;s thread?

When to use handler.post() &amp; when to new Thread()

Consider a variable `x` containing a floating point number. I want to use matplotlib&#39;s colormaps to map this number to a color, but not plot anything. Basically, I want to be able to choose the colormap with `mpl.cm.autumn` for example, use `mpl.colors.Normalize(vmin = -20, vmax = 10)` to set the range, and then map `x` to the corresponding color. But I really don&#39;t get the documentation of `mpl.cm`, so if anyone could give me a hint.

How to map number to color using matplotlib&#39;s colormap?

<p>Consider a variable <code>x</code> containing a floating point number. I want to use matplotlib's colormaps to map this number to a color, but not plot anything. Basically, I want to be able to choose the colormap with <code>mpl.cm.autumn</code> for example, use <code>mpl.colors.Normalize(vmin = -20, vmax = 10)</code> to set the range, and then map <code>x</code> to the corresponding color. But I really don't get the documentation of <code>mpl.cm</code>, so if anyone could give me a hint.</p>


How can I pass an integer by reference in Python?

I want to modify the value of a variable that I am passing to the function. I have read that everything in Python is pass by value, but there has to be an easy trick. For example, in Java you could pass the reference types of `Integer`, `Long`, etc.

 1. How can I pass an integer into a function by reference?
 2. What are the best practices?



Passing an integer by reference in Python

At the moment I am running `python manage.py test` every once in a while after I make significant changes in my django project. Is it possible to run those tests automatically whenever I change and save a file in my project? It&#39;ll be useful to detect bugs earlier (I know rails has something like this with rspec). I am using nose and django-nose. Thanks in advance.

How to automatically run tests when there&#39;s any change in my project (Django)?

I&#39;m writing a Python script that needs to write some data to a temporary file, then create a subprocess running a C++ program that will read the temporary file.  I&#39;m trying to use [`NamedTemporaryFile`](http://docs.python.org/2/library/tempfile.html#tempfile.NamedTemporaryFile) for this, but according to the docs,

&gt; Whether the name can be used to open the file a second time, while the named temporary file is still open, varies across platforms (it can be so used on Unix; it cannot on Windows NT or later).

And indeed, on Windows if I flush the temporary file after writing, but don&#39;t close it until I want it to go away, the subprocess isn&#39;t able to open it for reading.

I&#39;m working around this by creating the file with `delete=False`, closing it before spawning the subprocess, and then manually deleting it once I&#39;m done:

    fileTemp = tempfile.NamedTemporaryFile(delete = False)
    try:
        fileTemp.write(someStuff)
        fileTemp.close()
        # ...run the subprocess and wait for it to complete...
    finally:
        os.remove(fileTemp.name)

This seems inelegant.  Is there a better way to do this?  Perhaps a way to open up the permissions on the temporary file so the subprocess can get at it?

How to create a temporary file that can be read by a subprocess?

After dive into Python&#39;s source code, I find out that it maintains an array of `PyInt_Object`s ranging from `int(-5)` to `int(256)` (@src/Objects/intobject.c)

A little experiment proves it:

    &gt;&gt;&gt; a = 1
    &gt;&gt;&gt; b = 1
    &gt;&gt;&gt; a is b
    True
    &gt;&gt;&gt; a = 257
    &gt;&gt;&gt; b = 257
    &gt;&gt;&gt; a is b
    False

But if I run those code together in a py file (or join them with semi-colons), the result is different:

    &gt;&gt;&gt; a = 257; b = 257; a is b
    True

I&#39;m curious why they are still the same object, so I digg deeper into the syntax tree and compiler, I came up with a calling hierarchy listed below:

&lt;!-- language: lang-none --&gt;

    PyRun_FileExFlags() 
        mod = PyParser_ASTFromFile() 
            node *n = PyParser_ParseFileFlagsEx() //source to cst
                parsetoke() 
                    ps = PyParser_New() 
                    for (;;)
                        PyTokenizer_Get() 
                        PyParser_AddToken(ps, ...)
            mod = PyAST_FromNode(n, ...)  //cst to ast
        run_mod(mod, ...)
            co = PyAST_Compile(mod, ...) //ast to CFG
                PyFuture_FromAST()
                PySymtable_Build()
                co = compiler_mod()
            PyEval_EvalCode(co, ...)
                PyEval_EvalCodeEx()

Then I added some debug code in `PyInt_FromLong` and before/after `PyAST_FromNode`, and executed a test.py:

    a = 257
    b = 257
    print &quot;id(a) = %d, id(b) = %d&quot; % (id(a), id(b))

the output looks like:

&lt;!-- language: lang-none --&gt;

    DEBUG: before PyAST_FromNode
    name = a
    ival = 257, id = 176046536
    name = b
    ival = 257, id = 176046752
    name = a
    name = b
    DEBUG: after PyAST_FromNode
    run_mod
    PyAST_Compile ok
    id(a) = 176046536, id(b) = 176046536
    Eval ok

It means that during the `cst` to `ast` transform, two different `PyInt_Object`s are created (actually it&#39;s performed in the `ast_for_atom()` function), but they are later merged.

I find it hard to comprehend the source in `PyAST_Compile` and `PyEval_EvalCode`, so I&#39;m here to ask for help, I&#39;ll be appreciative if some one gives a hint?


What&#39;s with the integer cache maintained by the interpreter?

From https://stackoverflow.com/questions/12118720/python-tf-idf-cosine-to-find-document-similarity , it is possible to calculate document similarity using tf-idf cosine. Without importing external libraries, are that any ways to calculate cosine similarity between 2 strings?


    s1 = &quot;This is a foo bar sentence .&quot;
    s2 = &quot;This sentence is similar to a foo bar sentence .&quot;
    s3 = &quot;What is this string ? Totally not related to the other two lines .&quot;
    
    cosine_sim(s1, s2) # Should give high cosine similarity
    cosine_sim(s1, s3) # Shouldn&#39;t give high cosine similarity value
    cosine_sim(s2, s3) # Shouldn&#39;t give high cosine similarity value





Calculate cosine similarity given 2 sentence strings

I need your help! I have a plotting code which is the following:

    fig = plt.figure()
    ax1 = fig.add_subplot(111)

    imax1 = ax1.imshow(data,interpolation = &#39;nearest&#39;, origin = &#39;lower&#39;,cmap=cm.jet)#plot
    cbar = plt.colorbar(imax1, extend=&#39;neither&#39;, spacing=&#39;proportional&#39;,
                    orientation=&#39;vertical&#39;, shrink=0.7, format=&quot;%.0f&quot;)
    cbar.set_label(r&quot;ET [mm/month]&quot;, size=10)

    titlestr = &quot;Evapotranspiration in mm/month&quot;
    plt.title(titlestr)
    #plt.xlabel(&quot;Longitude&quot;)
    #plt.ylabel(&quot;Latitude&quot;)
    imax1.set_clim(0,60)
    labels = [item.get_text() for item in ax1.get_xticklabels()]
    for ii in range(np.shape(labels)[0]):
        labels[ii] = str(grid_lon[75*ii/np.shape(labels)[0]])

    ax1.set_xticklabels(labels, rotation = 45, ha=&#39;right&#39;, size = 10)

    labels = [item.get_text() for item in ax1.get_yticklabels()]
    for ii in range(np.shape(labels)[0]):
        labels[ii] = str(grid_lat[75*ii/np.shape(labels)[0]])

    ax1.set_yticklabels(labels, size = 10)

    pngname = &quot;./out/2d_&quot;+variable+&quot;_&quot;+mm+&quot;.png&quot;
    print &quot;save &quot;, pngname
    plt.savefig(pngname, dpi=None, facecolor=&#39;w&#39;, edgecolor=&#39;w&#39;,
        orientation=&#39;portrait&#39;, papertype=None, format=None,
        transparent=False, bbox_inches=None, pad_inches=0.1)


    print &quot;plot finished&quot;
    
I would like to set the label size of the colorbar labels (e.g. 0,10,20,...60) to size of 10 or smaller. This will probably go into the line &quot;imax1.set_clim(0,60). Any ideas? I&#39;d be also interested to print information of the imax1 object to command line. How could I do that? E.g. available attributes and functions of imax1.

I deeply appreciate your help!


Python matplotlib decrease size of colorbar labels

I need to create a figure in a file without displaying it within IPython notebook. I am not clear on the interaction between `IPython` and `matplotlib.pylab` in this regard. But, when I call `pylab.savefig(&quot;test.png&quot;)` the current figure get&#39;s displayed in addition to being saved in `test.png`. When automating the creation of a large set of plot files, this is often undesirable. Or in the situation that an intermediate file for external processing by another app is desired.

Not sure if this is a `matplotlib` or `IPython` notebook question.

Calling pylab.savefig without display in ipython

The default colors used in matplotlib (example here: http://matplotlib.org/examples/pylab_examples/pie_demo.html) are kind of plain and ugly. I&#39;ve also noticed that if you plot more than 5-6 different series in a single plot, matplotlib starts repeating colors.

I&#39;ve seen some gorgeous graphs coming out of other visualization packages (in other languages, by default) that can have 5-6 different series covered by just one color in different shades. Does anyone have a good color set to use in matplotlib? And a way to make matplotlib use it by default?

Prettier default plot colors in matplotlib

I am using matplotlib to make some graphs and unfortunately I cannot export them without the white background. 

![sample plot with solid white background][1]

In other words, when I export a plot like this and position it on top of another image, the white background hides what is behind it rather than allowing it to show through. How can I export plots with a transparent background instead?

  [1]: http://i.stack.imgur.com/wfysS.png



How to export plots from matplotlib with transparent background?

I would like to limit the X and Y axis in matplotlib for a specific subplot.
The subplot figure itself doesn&#39;t have any axis property. I want for example to change only the limits for the second plot:


    import matplotlib.pyplot as plt
    fig=plt.subplot(131)
    plt.scatter([1,2],[3,4])
    fig=plt.subplot(132)
    plt.scatter([10,20],[30,40])
    fig=plt.subplot(133)
    plt.scatter([15,23],[35,43])
    plt.show()



Content Type	Original Author	Original Content on Stackoverflow
Question	Psirus	View Question on Stackoverflow
Solution 1 - Python	David Zwicker	View Answer on Stackoverflow
Solution 2 - Python	ImportanceOfBeingErnest	View Answer on Stackoverflow
Solution 3 - Python	khnh123	View Answer on Stackoverflow

How to map number to color using matplotlib's colormap?

Python Problem Overview

Python Solutions

Solution 1 - Python

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Solution 3 - Python

When to use handler.post() & when to new Thread()

assigning class variable as default value to class method argument

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