If you want the number of bytes in a string, this function should do it for you pretty solidly. 

    def utf8len(s):
        return len(s.encode(&#39;utf-8&#39;))


The reason you got weird numbers is because encapsulated in a string is a bunch of other information due to the fact that strings are actual objects in python. 

Its interesting because if you look at my solution to encode the string into &#39;utf-8&#39;, there&#39;s an &#39;encode&#39; method on the &#39;s&#39; object (which is a string). Well, it needs to be stored somewhere right? Hence, the higher than normal byte count. Its including that method, along with a few others :).


There&#39;s a caveat to the accepted answer. 

For some multi-byte encodings (e.g. utf-16), `string.encode` will add a *Byte Order Mark* (BOM) at the start, which is a sequence of special bytes that inform the reader on the [byte endianness][1] used. So the length you get is actually `len(BOM) + len(encoded_word)`.

If you don&#39;t want to count the BOM bytes, you can use either the little-endian version of the encoding (adding the suffix &quot;-le&quot;) or the big-endian version (adding the suffix &quot;be&quot;).

    &gt;&gt;&gt; len(&#39;ciao&#39;.encode(&#39;utf-16&#39;))
    10
    &gt;&gt;&gt; len(&#39;ciao&#39;.encode(&#39;utf-16-le&#39;))
    8



  [1]: https://en.wikipedia.org/wiki/Endianness

Android design support library now includes support for Snackbar.

I&#39;ve used the following code to create one:

    Snackbar.make(findViewById(R.id.root_layout), result, Snackbar.LENGTH_LONG)
            .setAction(&quot;Dismiss&quot;, new View.OnClickListener() {
                @Override
                public void onClick(View v) {
    
                }
            }).show();

The snackbar can be dismissed by a swipe. However, I also want to dismiss it using its own Action Button (created using the setAction function).

However there doesn&#39;t seem to be any function available that can do that.

How to dismiss a Snackbar using it&#39;s own Action button?

It seems Google finally closed all doors for getting the current foreground application package.

After the Lollipop update, which killed [`getRunningTasks(int maxNum)`][1] and thanks to [this answer][2], I used this code to get the foreground application package since Lollipop:

    final int PROCESS_STATE_TOP = 2;
    RunningAppProcessInfo currentInfo = null;
    Field field = null;
    try {
        field = RunningAppProcessInfo.class.getDeclaredField(&quot;processState&quot;);
    } catch (Exception ignored) { 
    }
    ActivityManager am = (ActivityManager) this.getSystemService(Context.ACTIVITY_SERVICE);
    List&lt;RunningAppProcessInfo&gt; appList = am.getRunningAppProcesses();
    for (RunningAppProcessInfo app : appList) {
        if (app.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND &amp;&amp;
            app.importanceReasonCode == 0 ) {
            Integer state = null;
            try {
                state = field.getInt( app );
            } catch (Exception ignored) {
            }
            if (state != null &amp;&amp; state == PROCESS_STATE_TOP) {
                currentInfo = app;
                break;
            }
        }
    }
    return currentInfo;

Android 5.1.1 and above (6.0 Marshmallow), it seems, killed [`getRunningAppProcesses()`][3] as well. It now returns a list of your own application package.

___

**UsageStatsManager**

We can use the new `UsageStatsManager` API as [described here][4] but it doesn&#39;t work for all applications. Some system applications will return the same package 

    com.google.android.googlequicksearchbox

___

**AccessibilityService** (December 2017: Going to be banned for use by Google)

Some applications use `AccessibilityService` (as [seen here][5]) but it has some disadvantages.

___

**Is there another way of getting the current running application package?**


  [1]: http://developer.android.com/intl/zh-cn/reference/android/app/ActivityManager.html#getRunningTasks(int)
  [2]: https://stackoverflow.com/a/28277427/444324
  [3]: http://developer.android.com/intl/zh-cn/reference/android/app/ActivityManager.html#getRunningAppProcesses()
  [4]: https://stackoverflow.com/a/26885469/444324
  [5]: https://stackoverflow.com/a/27642535/444324

Android 5.1.1 and above - getRunningAppProcesses() returns my application package only

I have a string that is to be sent over a network. I need to check the total bytes it is represented in.

`sys.getsizeof(string_name)` returns extra bytes. For example for `sys.getsizeof(&quot;a&quot;)` returns 22 , while one character is only represented in 1 byte in python. Is there some other method to find this ?

Python : Get size of string in bytes

<p>I have a string that is to be sent over a network. I need to check the total bytes it is represented in.</p>
<p><code>sys.getsizeof(string_name)</code> returns extra bytes. For example for <code>sys.getsizeof("a")</code> returns 22 , while one character is only represented in 1 byte in python. Is there some other method to find this ?</p>


I want to store my users location using longitude and latitude, at the moment this comes from Google Maps, but I will be using GeoDango and some point to work out distances between to points also. 

However, my first confusion is which field in Django I should be using to store the longitude and latitude values? The information I&#39;m getting is conflicting. 


The official documentation uses a ``FloatField``
https://docs.djangoproject.com/en/dev/ref/contrib/gis/tutorial/#geographic-models

    lon = models.FloatField()
    lat = models.FloatField()

Where almost every answer on stackoverflow shows a ``DecimalField``

    long = models.DecimalField(max_digits=8, decimal_places=3)
    lat = models.DecimalField(max_digits=8, decimal_places=3)

So what should I be using?



Which Model Field to use in Django to store longitude and latitude values?

How can I make [`@functools.lru_cache`][1] decorator ignore some of the function arguments with regard to caching key?

For example, I have a function that looks like this:

    def find_object(db_handle, query):
        # (omitted code)
        return result

If I apply `lru_cache` decorator just like that, `db_handle` will be included in the cache key. As a result, if I try to call the function with the same `query`, but different `db_handle`, it will be executed again, which I&#39;d like to avoid. I want `lru_cache` to consider `query` argument only.

  [1]: https://docs.python.org/3/library/functools.html#functools.lru_cache

Make @lru_cache ignore some of the function arguments

Consider simple Django models `Event` and `Participant`:

    class Event(models.Model):
        title = models.CharField(max_length=100)
    
    class Participant(models.Model):
        event = models.ForeignKey(Event, db_index=True)
        is_paid = models.BooleanField(default=False, db_index=True)
    
It&#39;s easy to annotate events query with total number of participants:

    events = Event.objects.all().annotate(participants=models.Count(&#39;participant&#39;))

**How to annotate with count of participants filtered by `is_paid=True`?**

I need to query **all events** regardless of number of participants, e.g. I don&#39;t need to filter by annotated result. If there are `0` participants, that&#39;s ok, I just need `0` in annotated value.

The [example from documentation](https://docs.djangoproject.com/en/1.8/topics/db/aggregation/#order-of-annotate-and-filter-clauses) doesn&#39;t work here, because it excludes objects from query instead of annotating them with `0`.

**Update.** Django 1.8 has new [conditional expressions feature](https://docs.djangoproject.com/en/1.8/ref/models/conditional-expressions/), so now we can do like this:

    events = Event.objects.all().annotate(paid_participants=models.Sum(
        models.Case(
            models.When(participant__is_paid=True, then=1),
            default=0,
            output_field=models.IntegerField()
        )))


**Update 2.** Django 2.0 has new [Conditional aggregation](https://docs.djangoproject.com/en/2.0/ref/models/conditional-expressions/#conditional-aggregation) feature, see [the accepted answer](https://stackoverflow.com/a/48649024/326406) below.

**Update 3.** For Django 3.x please [check this answer below](https://stackoverflow.com/a/70234015/326406).

How to filter objects for count annotation in Django?

I am trying to convert working Python 2.7 code into Python 3 code and I am receiving a type error from the urllib request module.

I used the inbuilt 2to3 Python tool to convert the below working urllib and urllib2 Python 2.7 code:

    import urllib2
    import urllib
    
    url = &quot;https://www.customdomain.com&quot;
    d = dict(parameter1=&quot;value1&quot;, parameter2=&quot;value2&quot;)
    
    req = urllib2.Request(url, data=urllib.urlencode(d))
    f = urllib2.urlopen(req)
    resp = f.read()


The output from the 2to3 module was the below Python 3 code:


    import urllib.request, urllib.error, urllib.parse
    
    url = &quot;https://www.customdomain.com&quot;
    d = dict(parameter1=&quot;value1&quot;, parameter2=&quot;value2&quot;)
    
    req = urllib.request.Request(url, data=urllib.parse.urlencode(d))
    f = urllib.request.urlopen(req)
    resp = f.read()





 
When the Python 3 code is run the following error is produced:

    ---------------------------------------------------------------------------
    TypeError                                 Traceback (most recent call last)
    &lt;ipython-input-56-206954140899&gt; in &lt;module&gt;()
          5 
          6 req = urllib.request.Request(url, data=urllib.parse.urlencode(d))
    ----&gt; 7 f = urllib.request.urlopen(req)
          8 resp = f.read()
    
    C:\Users\Admin\Anaconda3\lib\urllib\request.py in urlopen(url, data, timeout, cafile, capath, cadefault, context)
        159     else:
        160         opener = _opener
    --&gt; 161     return opener.open(url, data, timeout)
        162 
        163 def install_opener(opener):
    
    C:\Users\Admin\Anaconda3\lib\urllib\request.py in open(self, fullurl, data, timeout)
        459         for processor in self.process_request.get(protocol, []):
        460             meth = getattr(processor, meth_name)
    --&gt; 461             req = meth(req)
        462 
        463         response = self._open(req, data)
    
    C:\Users\Admin\Anaconda3\lib\urllib\request.py in do_request_(self, request)
       1110                 msg = &quot;POST data should be bytes or an iterable of bytes. &quot; \
       1111                       &quot;It cannot be of type str.&quot;
    -&gt; 1112                 raise TypeError(msg)
       1113             if not request.has_header(&#39;Content-type&#39;):
       1114                 request.add_unredirected_header(
    
    TypeError: POST data should be bytes or an iterable of bytes. It cannot be of type str.



I have also read two other tickets ([ticket1][1] and [ticket2][2]) which mentioned encoding the date. 

When I changed the line `f = urllib.request.urlopen(req)` to `f = urllib.request.urlopen(req.encode(&#39;utf-8&#39;))` I received the following error: `AttributeError: &#39;Request&#39; object has no attribute &#39;encode&#39;`

I am stuck as to how to make the Python 3 code work. Could you please help me?


  [1]: https://stackoverflow.com/questions/28850421/post-data-should-be-bytes-or-an-iterable-of-bytes-it-cannot-be-of-type-str
  [2]: https://stackoverflow.com/questions/5440485/typeerror-post-data-should-be-bytes-or-an-iterable-of-bytes-it-cannot-be-str

Python 3 urllib produces TypeError: POST data should be bytes or an iterable of bytes. It cannot be of type str

I have a simple python code as follows:


    import numpy as np
    import matplotlib.pyplot as plt

    &quot;&quot;&quot;
    Here are the solutions and the plot.
    &quot;&quot;&quot;
    
    # Create the axis and plot.
    plt.axis([0, 10, 0, 10])
    axis_x = range(1, 11)
    grd = [1.1, 2.1, 3.1, 4.1, 5.1, 6.1, 7.1, 8.1, 9.1, 10.1]
    grd2 = [1.2, 2.2, 3.2, 4.2, 5.2, 6.2, 7.2, 8.2, 9.2, 10.2]
    plt.plot(axis_x, grd, &#39;-g&#39;, label=&#39;BR1&#39;)
    plt.plot(axis_x, grd2, &#39;-b&#39;, label=&#39;BR2&#39;)
    plt.legend(loc=&#39;upper left&#39;)
    plt.grid()
    plt.show()
    
    # Save the results vector to a text file.
    np.savetxt(&#39;test.out&#39;, (grd, grd2))
    
    # Save the figure as &#39;.eps&#39; file.
    plt.savefig(&#39;expl.pdf&#39;, format=&#39;pdf&#39;, dpi=1200)

When I open the output files `expl.pdf` and/or `test.out` I find them blank and nothing in there. Why?

Thanks.

Content Type	Original Author	Original Content on Stackoverflow
Question	Iffat Fatima	View Question on Stackoverflow
Solution 1 - Python	Kris	View Answer on Stackoverflow
Solution 2 - Python	janluke	View Answer on Stackoverflow

Python : Get size of string in bytes

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

Android 5.1.1 and above - getRunningAppProcesses() returns my application package only

How to dismiss a Snackbar using it's own Action button?

Attributions