Use the [`gca`](https://matplotlib.org/api/_as_gen/matplotlib.pyplot.gca.html?highlight=gca#matplotlib.pyplot.gca) (&quot;get current axes&quot;) helper function:

    ax = plt.gca()

Example:


    import matplotlib.pyplot as plt
    import matplotlib.finance
    quotes = [(1, 5, 6, 7, 4), (2, 6, 9, 9, 6), (3, 9, 8, 10, 8), (4, 8, 8, 9, 8), (5, 8, 11, 13, 7)]
    ax = plt.gca()
    h = matplotlib.finance.candlestick(ax, quotes)
    plt.show()

![enter image description here][1]


  [1]: http://i.stack.imgur.com/uiWWL.png

You can either 

    fig, ax = plt.subplots()  #create figure and axes
    candlestick(ax, quotes, ...)

or 

    candlestick(plt.gca(), quotes) #get the axis when calling the function

The first gives you more flexibility. The second is much easier if candlestick is the only thing you want to plot

I am using RequireJS and need to initialize something on DOM ready. Now, RequireJS provides the [`domReady` plugin][1], but we already have jQuery&#39;s `$(document).ready()`, which is available to me since I have required jQuery.

So I have got two options:

 1. Use the `domReady` plugin:

        require([&#39;domReady&#39;], function (domReady) {
            domReady(function () {
                // Do my stuff here...
            });
        });

 2. Use `$(document).ready()`:

        $(document).ready(function() {
            // Do my stuff here...
        });

**Which one should I choose, and why?**

 Both the options seems to work as expected. I am not confident in the jQuery&#39;s one because RequireJS is doing its magic; that is, since RequireJS will dynamically add scripts, I&#39;m worried that DOM ready may occur before all of the dynamically-requested scripts are loaded. Whereas, RequireJS will add a burden on additional JS just for `domReady` when I already have jQuery required.

## Questions

- Why does RequireJS provide a `domReady` plugin when we can have jQuery&#39;s `$(document).ready();`? I don&#39;t see any advantage of including another dependency.
- If its just to feed a need, then why not provide one for cross-browser AJAX?

As far as I know, a module that requires `domReady` won&#39;t be fetched or executed after the document is ready, and you could do the same requiring jQuery as well:

    require([&#39;jQuery&#39;], function ($) {
        $(document).ready(function () {
            // Do my stuff here...
        });
    });

To be more clear on my question: **what&#39;s the difference between requiring `domReady` or `jQuery`?**


  [1]: http://requirejs.org/docs/api.html#pageload
  [2]: http://stackoverflow.com/a/15364273/320399

Requirejs domReady plugin vs Jquery $(document).ready()?

Is it possible to determine the cardinality of a c++ `enum class`:

    enum class Example { A, B, C, D, E };

I tried to use `sizeof`, however, it returns the size of an enum element.

    sizeof(Example); // Returns 4 (on my architecture)

Is there a standard way to get the cardinality (5 in my example) ?

Is it possible to determine the number of elements of a c++ enum class?

I need to make a candlestick chart (something like this) using some stock data. For this I want to use the function [matplotlib.finance.candlestick()][1]. To this function I need to supply quotes and &quot;*an Axes instance to plot to*&quot;. I created some sample quotes as follows: 

    quotes = [(1, 5, 6, 7, 4), (2, 6, 9, 9, 6), (3, 9, 8, 10, 8), (4, 8, 8, 9, 8), (5, 8, 11, 13, 7)]
I now also need an Axes instance though, at which I am a bit lost. I created plots before using matplotlib.pyplot. I think I now need to do something with [matplotlib.axes][2] though, but I am unsure what exactly.

Could anybody help me out a little bit here? All tips are welcome!


  [1]: https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/finance.py
  [2]: http://matplotlib.org/api/axes_api.html

How to get a matplotlib Axes instance to plot to?

I need to make a candlestick chart (something like this) using some stock data. For this I want to use the function <a href="https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/finance.py" target="_blank" rel="noopener noreferrer">matplotlib.finance.candlestick()</a>. To this function I need to supply quotes and "an Axes instance to plot to". I created some sample quotes as follows:
<pre><code class="hljs language-css">quotes = [(1, 5, 6, 7, 4), (2, 6, 9, 9, 6), (3, 9, 8, 10, 8), (4, 8, 8, 9, 8), (5, 8, 11, 13, 7)]
</code></pre>
I now also need an Axes instance though, at which I am a bit lost. I created plots before using matplotlib.pyplot. I think I now need to do something with <a href="http://matplotlib.org/api/axes_api.html" target="_blank" rel="noopener noreferrer">matplotlib.axes</a> though, but I am unsure what exactly.
Could anybody help me out a little bit here? All tips are welcome!

I have an image and I want to extract a region from it. I have coordinates of left upper corner and right lower corner of this region. In gray scale I do it like this:

    I = cv2.imread(&quot;lena.png&quot;)
    I = cv2.cvtColor(I, cv2.COLOR_RGB2GRAY)
    region = I[248:280,245:288]
    tools.show_1_image_pylab(region)

I can&#39;t figure it out how to do it in color. I thought of extracting each channel R, G, B; slicing this region from each of the channels and to merge them back together but there is gotta be a shorter way. 



Extracting a region from an image using slicing in Python, OpenCV

I&#39;m checking to see if a directory exists, but I noticed I&#39;m using `os.path.exists` instead of `os.path.isdir`.  Both work just fine, but I&#39;m curious as to what the advantages are for using `isdir` instead of `exists`. 

pros and cons between os.path.exists vs os.path.isdir

I am very confused by the behaviour below. Cases 1, 3, and 4 perform as I would expect, but case 2 does not. Why does case 2 allow the function to change the value of the dictionary entry globally, even though the dictionary is never returned by the function? A main reason I am using functions is to isolate everything in the function from the rest of the code, but this does not seem to be possible if I choose to use the same variable names inside of the function. I was under the understanding that anything explicitly defined in a function is local to that function, but this does not seem to be the case if the dictionary is **defined and passed as an input to the function**.



    Python 2.7.2+ (default, Oct  4 2011, 20:06:09) 
    [GCC 4.6.1] on linux2
    Type &quot;help&quot;, &quot;copyright&quot;, &quot;credits&quot; or &quot;license&quot; for more information.

=============Case 1===============

    &gt;&gt;&gt; def testfun1(a):
    ...     a=2
    ... 
    &gt;&gt;&gt; a=0
    &gt;&gt;&gt; testfun1(a)
    &gt;&gt;&gt; a
    0

=============Case 2===============

    &gt;&gt;&gt; def testfun2(b):
    ...     b[&#39;test&#39;]=2
    ... 
    &gt;&gt;&gt; b={}
    &gt;&gt;&gt; testfun2(b)
    &gt;&gt;&gt; b
    {&#39;test&#39;: 2}


=============Case 3===============

    &gt;&gt;&gt; def testfun3():
    ...     c=2
    ... 
    &gt;&gt;&gt; c=0
    &gt;&gt;&gt; testfun3()
    &gt;&gt;&gt; c
    0


=============Case 4===============
(explained by this question: https://stackoverflow.com/questions/14323817/global-dictionaries-dont-need-keyword-global-to-modify-them)

    &gt;&gt;&gt; def testfun4():
    ...     d[&#39;test&#39;]=10
    ... 
    &gt;&gt;&gt; d={}
    &gt;&gt;&gt; testfun4()
    &gt;&gt;&gt; d
    {&#39;test&#39;: 10}


python dictionary passed as an input to a function acts like a global in that function rather than a local

I&#39;m trying to learn python and I now I am trying to get the hang of classes and how to manipulate them with instances.

I can&#39;t seem to understand this practice problem:

Create and return a student object whose name, age, and major are
the same as those given as input

    def make_student(name, age, major)

I just don&#39;t get what it means by object, do they mean I should create an array inside the function that holds these values? or create a class and let this function be inside it, and assign instances? (before this question i was asked to set up a student class with name, age, and major inside)

    class Student:
	    name = &quot;Unknown name&quot;
	    age = 0
	    major = &quot;Unknown major&quot;

Python, creating objects

I [saw](https://github.com/mitsuhiko/flask/blob/master/CHANGES) that `g` will move from the request context to the app context in Flask 0.10, which made me confused about the intended use of `g`.

My understanding (for Flask 0.9) is that:

 * `g` lives in the request context, i.e., created afresh when the requests starts, and available until it ends
 * `g` is intended to be used as a &quot;request blackboard&quot;, where I can put stuff relevant for the duration of the request (i.e., set a flag at the beginning of the request and handle it at the end, possibly from a `before_request`/`after_request` pair)
 * in addition to holding request-level-state, `g` can and should be used for resource management, i.e., holding database connections, etc.


Which of these sentences are no longer true in Flask 0.10? Can someone point me to a resource discussing the _reasons_ for the change? What should I use as a &quot;request blackboard&quot; in Flask 0.10 - should I create my own app/extension specific thread-local proxy and push it to the context stack `before_request`? What&#39;s the point of resource management at the application context, if my application lives for a long while (not like a request) and thus the resources are never freed?

When should Flask.g be used?

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?

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 need to download in some way a list of all stock symbol of specified market.

I&#39;ve found in [this link][1] ho can I do it someway. 

It uses following link in order to retrieve stock list that statisfies some parameters:

https://www.google.com/finance?start=0&amp;num=3000&amp;q=%5B(exchange%20%3D%3D%20%22NASDAQ%22)%20%26%20(last_price%20%3E%200.1)%20%26%20(last_price%20%3C%201500)%5D&amp;restype=company&amp;noIL=1

I&#39;ve modified the query removing contraints

https://www.google.com/finance?q=%5B%28exchange+%3D%3D+%22NASDAQ%22%29%5D

Now I have all stock list but in a web page that I must navigate.

Is there a way to obtain the full list in some standard format, like xml, json or whatever?


  [1]: https://stackoverflow.com/questions/6008880/get-complete-stock-list-for-specific-index

Download all stock symbol list of a market

If you want to insert a small plot inside a bigger one you can use [Axes][1], like [here][2].

The problem is that I don&#39;t know how to do the same inside a subplot.

I have several subplots and I would like to plot a small plot inside each subplot.
The example code would be something like this:


    import numpy as np
    import matplotlib.pyplot as plt

    fig = plt.figure()

    for i in range(4):
        ax = fig.add_subplot(2,2,i)
        ax.plot(np.arange(11),np.arange(11),&#39;b&#39;)

        #b = ax.axes([0.7,0.7,0.2,0.2]) 
        #it gives an error, AxesSubplot is not callable

        #b = plt.axes([0.7,0.7,0.2,0.2])
        #plt.plot(np.arange(3),np.arange(3)+11,&#39;g&#39;)
        #it plots the small plot in the selected position of the whole figure, not inside the subplot

Any ideas?

Thanks in advance!


  [1]: http://scipy-lectures.github.io/intro/matplotlib/matplotlib.html#axes
  [2]: http://matplotlib.org/examples/pylab_examples/axes_demo.html

Embedding small plots inside subplots in matplotlib

I&#39;m very new to Python and programming in general, so apologies in advance if I&#39;m missing something obvious. I&#39;m trying to plot a graph and label the axes, but every time I try to label the y axis an exception is raised. I wrote the code below in a new script to make sure the problem wasn&#39;t coming from somewhere else in the module. I&#39;m using Python 3.4.

    from numpy import *
    from matplotlib import *
    
    a = [1, 2, 3, 4, 5]
    b = [2, 3, 2, 3, 2]
    pyplot.plot(a, b)
    pylab.xlabel(&quot;Time&quot;)
    pylab.ylabel(&quot;Speed&quot;)

Every time, I get the error &#39;TypeError: &#39;str&#39; object is not callable&#39; for the final line. If I change the y to an x, everything is fine. If I change the x to a y, I get the same error. However, ylabel comes up on the drop down list for ylabel so the function does exist and the documentation says a string is the only necessary argument, exactly as for xlabel (matplotlib.pyplot.ylabel(s, *args, **kwargs) and matplotlib.pyplot.xlabel(s, *args, **kwargs)). What on earth could be going on here?

Strange error with matplotlib axes labels

In a previous [answer][1] it was recommended to me to use `add_subplot` instead of `add_axes` to show axes correctly, but searching the documentation I couldn&#39;t understand when and why I should use either one of these functions. 

Can anyone explain the differences?


  [1]: https://stackoverflow.com/a/43283905

Content Type	Original Author	Original Content on Stackoverflow
Question	kramer65	View Question on Stackoverflow
Solution 1 - Python	wim	View Answer on Stackoverflow
Solution 2 - Python	Francesco Montesano	View Answer on Stackoverflow

How to get a matplotlib Axes instance to plot to?

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

Is it possible to determine the number of elements of a c++ enum class?

Requirejs domReady plugin vs Jquery $(document).ready()?

Attributions