The backend mainly matters if you&#39;re embedding matplotlib in an application, in which case you need to use a backend (GTK, Qt, TkInter, WxWindows) which matches the toolkit you&#39;re using to build your application. If you&#39;re also using matplotlib in a simple interactive way, you&#39;ll also want to use a backend which matches what is available on your machine (GTK if you&#39;re running Gnome, Qt if you&#39;re running KDE, etc) (although most libs are already installed on most machines)

The drawing layer part of the backend (Cairo, Agg...) also matters in terms of functionalities: you can choose it depending on what that layer provides compared to what your application needs (anti aliasing, alpha channel, export formats...). So if you develop and test using TkAgg and other people run with e.g. TkCairo, some things might not work. OTOH, running with QtAgg would certainly work in a very similar way as long as you stick to the matplotlib API and don&#39;t reach in the wrapped toolkit layer. 

I am new to *Web SQL database* and I use it to save data in a local database in a web page.

　I can ***create*** a ***database*** by

    var db = openDatabase(&#39;database&#39;, &#39;1.0&#39;, &#39;my database&#39;, 2 * 1024 * 1024);

　and I can ***create*** a ***table*** by doing this

    db.transaction(function (tx) {
      tx.executeSql(&#39;CREATE TABLE IF NOT EXISTS mytable (blah,blah)&#39;);
    });


　I can ***delete*** the ***table*** by

    db.transaction(function (tx) {
      tx.executeSql(&#39;DROP TABLE mytable&#39;);
    });


　but is there a way to delete the ***`database`*** programmatically?

How to delete a database in WebSQL programmatically?

I am interested in creating a Java data structure similar to a stack that supports the following operations as efficiently as possible:

* Push, which adds a new element atop the stack,
* Pop, which removes the top element of the stack,
* Find-Max, which returns (but does not remove) the largest element of the stack, and
* Find-Min, which returns (but does not remove) the smallest element of the stack, and

What would be the fastest implementation of this data structure?  How might I go about writing it in Java?

Stack with find-min/find-max more efficient than O(n)?

    &gt;&gt;&gt; import matplotlib
    &gt;&gt;&gt; print matplotlib.rcsetup.all_backends
    [u&#39;GTK&#39;, u&#39;GTKAgg&#39;, u&#39;GTKCairo&#39;, u&#39;MacOSX&#39;, u&#39;Qt4Agg&#39;, u&#39;Qt5Agg&#39;, u&#39;TkAgg&#39;, u&#39;WX&#39;, u&#39;WXAgg&#39;, u&#39;CocoaAgg&#39;, u&#39;GTK3Cairo&#39;, u&#39;GTK3Agg&#39;, u&#39;WebAgg&#39;, u&#39;nbAgg&#39;, u&#39;agg&#39;, u&#39;cairo&#39;, u&#39;emf&#39;, u&#39;gdk&#39;, u&#39;pdf&#39;, u&#39;pgf&#39;, u&#39;ps&#39;, u&#39;svg&#39;, u&#39;template&#39;]

Look at all those backends!  

Do I need to care which backend is in use?  e.g. if I develop and test my stuff using only `TkAgg` backend, and someone else using my code might be using `GTKAgg` backend on their system, might my stuff break for them in a way that I won&#39;t have noticed - or are all backends required to more or less &quot;work&quot; the same way? 



matplotlib backends - do I care?

<pre><code class="hljs language-python">>>> import matplotlib
>>> print matplotlib.rcsetup.all_backends
[u'GTK', u'GTKAgg', u'GTKCairo', u'MacOSX', u'Qt4Agg', u'Qt5Agg', u'TkAgg', u'WX', u'WXAgg', u'CocoaAgg', u'GTK3Cairo', u'GTK3Agg', u'WebAgg', u'nbAgg', u'agg', u'cairo', u'emf', u'gdk', u'pdf', u'pgf', u'ps', u'svg', u'template']
</code></pre>
Look at all those backends!
Do I need to care which backend is in use? e.g. if I develop and test my stuff using only <code>TkAgg</code> backend, and someone else using my code might be using <code>GTKAgg</code> backend on their system, might my stuff break for them in a way that I won't have noticed - or are all backends required to more or less "work" the same way?

I have `url` from the user and I have to reply with the fetched HTML.

How can I check for the URL to be malformed or not?

For example :

    url = &#39;google&#39; # Malformed
    url = &#39;google.com&#39; # Malformed
    url = &#39;http://google.com&#39; # Valid
    url = &#39;http://google&#39; # Malformed


How to validate a url in Python? (Malformed or not)

Say I have a python file in directory **e** like this:

*/a/b/c/d/e/file.py*

Under directory **e** I have a few folders I want to access but if file.py is executed from anywhere else rather than from folder **e** the relative path won&#39;t work for me. Also folder **e** could be located anywhere but always with the a set of sub folders so absolute path will not work.

First, is there any function to get the absolute path in relation to the source files location?

If not, any ideas how to sort this out? Grab the command line used and add the CWD together?

My problem here is that this folder are being installed on 20 different machines and OS&#39;s and I want it to be as dynamic as possible with little configurations and &quot;rules&quot; where it has to be installed etc.

Get location of the .py source file

**Short Question**  
What is the default order of a list returned from a Django filter call when connected to a PostgreSQL database?  

**Background**  
By my own admission, I *had* made a poor assumption at the application layer in that the order in which a list is returned will be constant, that is without using &#39;order_by&#39;.  The list of items I was querying is not in alphabetic order or any other **deliberate** order.  It was thought to remain in the same order as which they were added to the database.  

This assumption held true for hundreds of queries, but a failure was reported by my application when the order changed unknowingly.  To my knowledge, none of these records were touched during this time as I am the only person who maintains the DB.  To add to the confusion, when running the Django app on Mac OS X, it still worked as expected, but on Win XP, it changed the order.  (Note that the mentioned hundreds of queries was on Win XP).  

Any insight to this would be helpful as I could not find anything in the Django or PostgreSQL documentation that explained the differences in operating systems. 

**Example Call**  

    required_tests = Card_Test.objects.using(get_database()).filter(name__icontains=key)


**EDIT**  
After speaking with some colleague&#39;s of mine today, I had come up with the same answer as Bj&#246;rn Lindqvist.  

Looking back, I definitely understand why this is done wrong so often.  One of the benefits to using an ORM Django, sqlalchemy, or whatever is that you can write commands without having to know or understand (in detail) the database it&#39;s connected to.  Admittedly I happen to have been one of these users.  However on the flip-side of this is that without knowing the database in detail debugging errors like this are quite troublesome and potentially catastrophic.  

What is the default order of a list returned from a Django filter call?

I have an array. The valid values are not zero (either positive or negetive). I want to find the minimum and maximum within the array which should not take zeros into account. For example if the numbers are only negative. Zeros will be problematic.


Find the min/max excluding zeros in a numpy array (or a tuple) in python

I&#39;m trying to use the [Requests](http://docs.python-requests.org/en/latest/user/quickstart/#cookies) library to send cookies with a post request, but I&#39;m not sure how to actually set up the cookies based on its documentation. The script is for use on Wikipedia, and the cookie(s) that need to be sent are of this form:

    enwiki_session=17ab96bd8ffbe8ca58a78657a918558e; path=/; domain=.wikipedia.com; HttpOnly

However, the `requests` documentation quickstart gives this as the only example:

    cookies = dict(cookies_are=&#39;working&#39;)

How can I encode a cookie like the above using this library? Do I need to make it with python&#39;s standard cookie library, then send it along with the POST request?

How to send cookies in a post request with the Python Requests library?

I heard that using `System.out.println` for logging purposes is a very bad practice and this may force the server to fail.

I don&#39;t use this approach but I am very interested in knowing why System.out.println could make so trash things when used in backend code.

Do not use System.out.println in server side code

My company has thousands of existing xml web services and is starting to adopt AngularJs for new projects.

The tutorial over at http://angularjs.org/ uses json services exclusively. It looks like they make a service call in the controller, parse the resulting JSON, and pass the resulting object directly to the view.

What do I do with XML? I see four options:

1. Parse it and pass the DOM object directly to the UI(view).

2. Put a JSON wrapper around my XML services on the server side.

3. convert the DOM object to JSON with some library on the client side and convert it back when I make the post/put requests.

4. Convert the DOM object to a JavaScript object manually on the client side.


What the correct approach and why?

How to handle XML services in AngularJS?

I tried to switch Backend with Keras (from TensorFlow to Theano) but did not manage.
I followed the temps described [here](https://keras.io/backend/) but it doesn&#39;t work. I created a keras.json in the keras&#39; directory (as it did not exist) but it doesn&#39;t change anything when I import it from Python.



How to switch Backend with Keras (from TensorFlow to Theano)

I&#39;m working with django 1.6.5 and python 2.7.
I have import feature in my app and I get error:

    OSError: [Errno 18] Invalid cross-device link

I have problem with this part of code:

    os.rename(db_temp, settings.DATABASES[&#39;bookmat&#39;][&#39;NAME&#39;])

code in settings:

    &#39;bookmat&#39;: {
        &#39;ENGINE&#39;: &#39;django.db.backends.sqlite3&#39;,
        &#39;NAME&#39;: &#39;/my_projects/book/db/bookmat.sqlite3&#39;,
    },



OSError: [Errno 18] Invalid cross-device link

I want to set the middle point of a colormap, i.e., my data goes from -5 to 10 and I want zero to be the middle point. I think the way to do it is by subclassing normalize and using the norm, but I didn&#39;t find any example and it is not clear to me, what exactly have I to implement?

Defining the midpoint of a colormap in matplotlib

I&#39;m writing a simple Python application that uses matplotlib to display a few figures on screen. The number of figures generated is based on user input and changes throughout the application&#39;s life. The user has the ability to issue a &quot;plot&quot; command to generate a new figure window with the selected data series. In order to improve the user experience, I would like to provide another command that would programmatically arrange all open figure windows in some convenient arrangement (e.g. tile them across the available screen space).

I believe to have found APIs that allow me to adjust the size of the figure window (in pixels), but haven&#39;t had any success in finding a way to set their absolute position on screen. Is there a way to do this without delving into the details of whatever backend is in use? I would like to do this in a backend-agnostic way so I can avoid relying upon implementation details that might change in the future.

How do you set the absolute position of figure windows with matplotlib?

I&#39;ve started with matplot and managed some basic plots, but now I find it hard to discover how to do some stuff I need now :(

My actual question is how to place a global title and global legend on a figure with subplots.

I&#39;m doing 2x3 subplots where I have a lot of different graphs in various colors (about 200). To distinguish (most) of them I wrote something like

    def style(i, total):
        return dict(color=jet(i/total),
                    linestyle=[&quot;-&quot;, &quot;--&quot;, &quot;-.&quot;, &quot;:&quot;][i%4],
                    marker=[&quot;+&quot;, &quot;*&quot;, &quot;1&quot;, &quot;2&quot;, &quot;3&quot;, &quot;4&quot;, &quot;s&quot;][i%7])

    fig=plt.figure()
    p0=fig.add_subplot(321)
    for i, y in enumerate(data):
        p0.plot(x, trans0(y), &quot;-&quot;, label=i, **style(i, total))
    # and more subplots with other transN functions

(any thoughts on this? :)) Each subplot has the same style function.

Now I&#39;m trying to get a global title for all subplots and also a global legend which explains all styles. Also I need to make the font tiny to fit all 200 styles on there (I don&#39;t need completely unique styles, but at least some attempt)

Can someone help me solve this task?



Matplotlib - global legend and title aside subplots

Help required on matplotlib. Yes, I did not forget calling the pyplot.show().

### $ ipython --pylab ###


    import matplotlib.pyplot as p 
    p.plot(range(20), range(20))
It returns `matplotlib.lines.Line2D at 0xade2b2c` as the output.

    p.show()
There is nothing to happen. No error message. No new window. Nothing. I install `matplotlib` by using pip and I didn&#39;t take any error messages. 

Details:

I use,

- Ubuntu
- IPython v0.11
- Python v2.6.6
- matplotlib v1.0.1


matplotlib does not show my drawings although I call pyplot.show()

I am building a small tool for data analysis and I have come to the point, where I have to plot the prepared data. The code before this produces the following two lists with equal length.

    t11 = [&#39;00&#39;, &#39;01&#39;, &#39;02&#39;, &#39;03&#39;, &#39;04&#39;, &#39;05&#39;, &#39;10&#39;, &#39;11&#39;, &#39;12&#39;, &#39;13&#39;, &#39;14&#39;, &#39;15&#39;, &#39;20&#39;, &#39;21&#39;, &#39;22&#39;, &#39;23&#39;, &#39;24&#39;, &#39;25&#39;, &#39;30&#39;, &#39;31&#39;, &#39;32&#39;, &#39;33&#39;, &#39;34&#39;, &#39;35&#39;, &#39;40&#39;, &#39;41&#39;, &#39;42&#39;, &#39;43&#39;, &#39;44&#39;, &#39;45&#39;, &#39;50&#39;, &#39;51&#39;, &#39;52&#39;, &#39;53&#39;, &#39;54&#39;, &#39;55&#39;]
    
    t12 = [173, 135, 141, 148, 140, 149, 152, 178, 135, 96, 109, 164, 137, 152, 172, 149, 93, 78, 116, 81, 149, 202, 172, 99, 134, 85, 104, 172, 177, 150, 130, 131, 111, 99, 143, 194]

Based on this, I want to built a histogram with matplotlib.plt.hist. However, there are a couple of problems:
 1. t11[x] and t12[x] are connected for all x. Where t11[x] is actually a string. It represents a certain detector combination. For example: &#39;01&#39; tells that the detection was made in the 0th segment of the first detector, and 1st segment of the second detector. My goal is to have each entry from t11 as a labeled point on the x axis. The t12 entry is going to define the hight of the bar above the t11 entry (on a logarithmic y axis)

How does one configure such an x axis?
 2. This is all very new to me. I could not find anything related in the documentation. Most probably because I did not know what to search for. SO: Is there an &quot;official&quot; name for what I am trying to achieve. This would also help me alot.



Content Type	Original Author	Original Content on Stackoverflow
Question	wim	View Question on Stackoverflow
Solution 1 - Python	gurney alex	View Answer on Stackoverflow

matplotlib backends - do I care?

Python Problem Overview

Python Solutions

Solution 1 - Python

Stack with find-min/find-max more efficient than O(n)?

How to delete a database in WebSQL programmatically?

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