The best way is to interact with the `axes` object directly

    import numpy as np
    import matplotlib.pyplot as plt
    x = np.arange(0, 10, 0.1)
    y1 = 0.05 * x**2
    y2 = -1 *y1
    
    fig, ax1 = plt.subplots()
    
    ax2 = ax1.twinx()
    ax1.plot(x, y1, &#39;g-&#39;)
    ax2.plot(x, y2, &#39;b-&#39;)
    
    ax1.set_xlabel(&#39;X data&#39;)
    ax1.set_ylabel(&#39;Y1 data&#39;, color=&#39;g&#39;)
    ax2.set_ylabel(&#39;Y2 data&#39;, color=&#39;b&#39;)
    
    plt.show()

![example graph][1]


  [1]: http://i.stack.imgur.com/K7727.png

There is a straightforward solution without messing with matplotlib: just pandas.

Tweaking the original example:

    table = sql.read_frame(query,connection)

    ax = table[0].plot(color=colors[0],ylim=(0,100))
    ax2 = table[1].plot(secondary_y=True,color=colors[1], ax=ax)
    
    ax.set_ylabel(&#39;Left axes label&#39;)
    ax2.set_ylabel(&#39;Right axes label&#39;)

Basically, when the `secondary_y=True` option is given (eventhough `ax=ax` is passed too) `pandas.plot` returns a different axes which we use to set the labels.

I know this was answered long ago, but I think this approach worths it.

I don&#39;t have access to Python right now, but off the top of my head:

    fig = plt.figure()

    axes1 = fig.add_subplot(111)
    # set props for left y-axis here

    axes2 = axes1.twinx()   # mirror them
    axes2.set_ylabel(...)

For everyone stumbling upon this post because pandas gets mentioned,
you now have the very elegant and straightforward option of [directly accessing the
secondary_y axis](https://pandas.pydata.org/pandas-docs/stable/user_guide/visualization.html#plotting-on-a-secondary-y-axis) in pandas with `ax.right_ax`  

So paraphrasing the example initially posted, you would write:  

    table = sql.read_frame(query,connection)

    ax = table[[0, 1]].plot(ylim=(0,100), secondary_y=table[1])
    ax.set_ylabel(&#39;$&#39;)
    ax.right_ax.set_ylabel(&#39;Your second Y-Axis Label goes here!&#39;)

(this is already mentioned in these posts as well: [1](https://stackoverflow.com/a/58047785) [2](https://stackoverflow.com/a/18078496))

Simple example with few loc:
```python3
plot(y1)
plt.gca().twinx().plot(y2, color = &#39;r&#39;) # default color is same as first ax
```

Explanation:
```python3
ax = plt.gca()    # Get current axis
ax2 = ax.twinx()  # make twin axis based on x
ax2.plot(...)     # ...
```


I&#39;m writing a WinForms application that transfers data to a USB HID class device.  My application uses the excellent Generic HID library v6.0 which can be found [here][1].  In a nutshell, when I need to write data to the device, this is the code that gets called:

    private async void RequestToSendOutputReport(List&lt;byte[]&gt; byteArrays)
    {
    	foreach (byte[] b in byteArrays)
    	{
    		while (condition)
    		{
                // we&#39;ll typically execute this code many times until the condition is no longer met
    	    	Task t = SendOutputReportViaInterruptTransfer();
    	    	await t;
    		}
    
    		// read some data from device; we need to wait for this to return
    		RequestToGetInputReport();
    	}
    }


When my code drops out of the while loop, I need to read some data from the device.  However, the device isn&#39;t able to respond right away so I need to wait for this call to return before I continue.  As it currently exists, RequestToGetInputReport() is declared like this:


    private async void RequestToGetInputReport()
    {
        // lots of code prior to this
        int bytesRead = await GetInputReportViaInterruptTransfer();
    }


For what it&#39;s worth, the declaration for GetInputReportViaInterruptTransfer() looks like this:

    internal async Task&lt;int&gt; GetInputReportViaInterruptTransfer()

Unfortunately, I&#39;m not very familiar with the workings of the new async/await technologies in .NET 4.5.  I did a little reading earlier about the await keyword and that gave me the impression that the call to GetInputReportViaInterruptTransfer() inside of RequestToGetInputReport() would wait (and maybe it does?) but it doesn&#39;t seem like the call to RequestToGetInputReport() itself is waiting because I seem to be re-entering the while loop almost immediately?

Can anyone clarify the behavior that I&#39;m seeing?


  [1]: http://janaxelson.com/hidpage.htm#MyExampleCode


How to wait for async method to complete?

Scott Meyers posted [content and status][1] of his next book EC++11.
He wrote that one item in the book could be *&quot;Avoid `std::enable_if` in function signatures&quot;*.

`std::enable_if` can be used as a function argument, as a return type or as a class template or function template parameter to conditionally remove functions or classes from overload resolution.

In [this question][2] all three solution are shown.

As function parameter:


    template&lt;typename T&gt;
    struct Check1
    {
       template&lt;typename U = T&gt;
       U read(typename std::enable_if&lt;
              std::is_same&lt;U, int&gt;::value &gt;::type* = 0) { return 42; }

       template&lt;typename U = T&gt;
       U read(typename std::enable_if&lt;
              std::is_same&lt;U, double&gt;::value &gt;::type* = 0) { return 3.14; }   
    };


As template parameter:

    template&lt;typename T&gt;
    struct Check2
    {
       template&lt;typename U = T, typename std::enable_if&lt;
                std::is_same&lt;U, int&gt;::value, int&gt;::type = 0&gt;
       U read() { return 42; }

       template&lt;typename U = T, typename std::enable_if&lt;
                std::is_same&lt;U, double&gt;::value, int&gt;::type = 0&gt;
       U read() { return 3.14; }   
    };


As return type:

    template&lt;typename T&gt;
    struct Check3
    {
       template&lt;typename U = T&gt;
       typename std::enable_if&lt;std::is_same&lt;U, int&gt;::value, U&gt;::type read() {
          return 42;
       }

       template&lt;typename U = T&gt;
       typename std::enable_if&lt;std::is_same&lt;U, double&gt;::value, U&gt;::type read() {
          return 3.14;
       }   
    };


  [1]: http://scottmeyers.blogspot.de/2013/01/effective-c11-content-and-status.html
  [2]: https://stackoverflow.com/questions/11055923/stdenable-if-parameter-vs-template-parameter

 * Which solution should be preferred and why should I avoid others? 
 * In which cases *&quot;Avoid `std::enable_if` in function signatures&quot;* concerns usage as return type (which is not part of normal function signature but of template specializations)?
 * Are there any differences for member and non-member function templates?

Why should I avoid std::enable_if in function signatures

I can add a y label to the left y-axis using `plt.ylabel`, but how can I add it to the secondary y-axis?


    table = sql.read_frame(query,connection)

    table[0].plot(color=colors[0],ylim=(0,100))
    table[1].plot(secondary_y=True,color=colors[1])
    plt.ylabel(&#39;$&#39;)





Adding a y-axis label to secondary y-axis in matplotlib

I can add a y label to the left y-axis using <code>plt.ylabel</code>, but how can I add it to the secondary y-axis?
<pre><code class="hljs language-css">table = sql.read_frame(query,connection)

table[0].plot(color=colors[0],ylim=(0,100))
table[1].plot(secondary_y=True,color=colors[1])
plt.ylabel('$')
</code></pre>

See the following code: 

    import datetime
    import pytz
    
    fmt = &#39;%Y-%m-%d %H:%M:%S %Z&#39;
    
    d = datetime.datetime.now(pytz.timezone(&quot;America/New_York&quot;))
    d_string = d.strftime(fmt)
    d2 = datetime.datetime.strptime(d_string, fmt)
    print d_string 
    print d2.strftime(fmt)

the output is 

    2013-02-07 17:42:31 EST
    2013-02-07 17:42:31 

The timezone information simply got lost in the translation. 

If I switch &#39;%Z&#39; to &#39;%z&#39;, I get

    ValueError: &#39;z&#39; is a bad directive in format &#39;%Y-%m-%d %H:%M:%S %z&#39;

I know I can use `python-dateutil`, but I just found it bizzare that I can&#39;t achieve this simple feature in datetime and have to introduce more dependency? 




Python datetime strptime() and strftime(): how to preserve the timezone information

Is there a Pythonic and efficient way to check whether a Numpy array contains at least one instance of a given row?  By &quot;efficient&quot; I mean it terminates upon finding the first matching row rather than iterating over the entire array even if a result has already been found.

With Python arrays this can be accomplished very cleanly with `if row in array:`, but this does not work as I would expect for Numpy arrays, as illustrated below.

With Python arrays:

    &gt;&gt;&gt; a = [[1,2],[10,20],[100,200]]
    &gt;&gt;&gt; [1,2] in a
    True
    &gt;&gt;&gt; [1,20] in a
    False

but Numpy arrays give different and rather odd-looking results. (The `__contains__` method of `ndarray` seems to be undocumented.)

    &gt;&gt;&gt; a = np.array([[1,2],[10,20],[100,200]])
    &gt;&gt;&gt; np.array([1,2]) in a
    True
    &gt;&gt;&gt; np.array([1,20]) in a
    True
    &gt;&gt;&gt; np.array([1,42]) in a
    True
    &gt;&gt;&gt; np.array([42,1]) in a
    False


testing whether a Numpy array contains a given row

I came across [this example][1] in the Matplotlib website. I was wondering if it was possible to increase the figure size.

I tried with

    f.figsize(15,15)

but it does nothing.

  [1]: http://matplotlib.org/examples/pylab_examples/subplots_demo.html


How do I change the figure size with subplots?

I have two scenarios where I need to pad a string with whitespaces up to a certain length, in both the left and right directions (in separate cases). For instance, I have the string:

    TEST

but I need to make the string variable

    _____TEST1

so that the actual string variable is 10 characters in length (led by 5 spaces in this case).
**NOTE**: I am showing underscores to represent whitespace (the markdown doesn&#39;t look right on SO otherwise).

I also need to figure out how to reverse it and pad whitespace from the other direction:

    TEST2_____

Are there any string helper functions to do this? Or would I need to create a character array to manage it?

Also note, that I am trying to keep the string length a variable (I used a length of 10 in the examples above, but I&#39;ll need to be able to change this).

Any help would be awesome. If there are any `python` functions to manage this, I&#39;d rather avoid having to write something from the ground up.

Thanks!
    

Python - How can I pad a string with spaces from the right and left?

I am trying to make a discrete colorbar for a scatterplot in matplotlib

I have my x, y data and for each point an integer tag value which I want to be represented with a unique colour, e.g.

    plt.scatter(x, y, c=tag)

typically tag will be an integer ranging from 0-20, but the exact range may change

so far I have just used the default settings, e.g.

    plt.colorbar()

which gives a continuous range of colours. Ideally i would like a set of n discrete colours (n=20 in this example). Even better would be to get a tag value of 0 to produce a gray colour and 1-20 be colourful.

I have found some &#39;cookbook&#39; scripts but they are very complicated and I cannot think they are the right way to solve a seemingly simple problem

Matplotlib discrete colorbar

I can import matplotlib but when I try to run the following:

    matplotlib.pyplot(x)

   I get:
    
    Traceback (most recent call last):
       File &quot;&lt;pyshell#31&gt;&quot;, line 1, in &lt;module&gt;
           matplotlib.pyplot(x)
    AttributeError: &#39;module&#39; object has no attribute &#39;pyplot&#39;



matplotlib has no attribute &#39;pyplot&#39;

In the pyplot document for scatter plot:

    matplotlib.pyplot.scatter(x, y, s=20, c=&#39;b&#39;, marker=&#39;o&#39;, cmap=None, norm=None,
                              vmin=None, vmax=None, alpha=None, linewidths=None,
                              faceted=True, verts=None, hold=None, **kwargs)

The marker size

&gt; s:
size in points^2. It is a scalar or an array of the same length as x and y.

What kind of unit is `points^2`? What does it mean? Does `s=100` mean `10 pixel x 10 pixel`?

Basically I&#39;m trying to make scatter plots with different marker sizes, and I want to figure out what does the `s` number mean.

pyplot scatter plot marker size

Check the x axis of the figure below. How can I move the labels a bit to the left so that they align with their respective ticks?

I&#39;m rotating the labels using:

    ax.set_xticks(xlabels_positions)
    ax.set_xticklabels(xlabels, rotation=45)

But, as you can see, the rotation is centered on the middle of the text labels. Which makes it look like they are shifted to the right.

I&#39;ve tried using this instead:

    ax.set_xticklabels(xlabels, rotation=45, rotation_mode=&quot;anchor&quot;)

... but it doesn&#39;t do what I wished for. And ``&quot;anchor&quot;`` seems to be the only value allowed for the ``rotation_mode`` parameter.


![Example][1]


  [1]: http://i.stack.imgur.com/LB7Vx.png

Content Type	Original Author	Original Content on Stackoverflow
Question	Osmond Bishop	View Question on Stackoverflow
Solution 1 - Python	Paul H	View Answer on Stackoverflow
Solution 2 - Python	kiril	View Answer on Stackoverflow
Solution 3 - Python	Micke	View Answer on Stackoverflow
Solution 4 - Python	Nimrod	View Answer on Stackoverflow
Solution 5 - Python	Hunaphu	View Answer on Stackoverflow

Adding a y-axis label to secondary y-axis in matplotlib

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

Solution 3 - Python

Solution 4 - Python

Solution 5 - Python

Why should I avoid std::enable_if in function signatures

How to wait for async method to complete?

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