I use pymongo 2.4.1.

    from bson.objectid import ObjectId
    [i for i in dbm.neo_nodes.find({&quot;_id&quot;: ObjectId(obj_id_to_find)})]



I was reading about it quite a bit in the past couple of hours, and I simply cannot see any reason (**valid** reason) to call `shutdown()` on the `ExecutorService`, unless we have a humongous application that stores, dozens and dozens of different executor services that are not used for a long time.

The only thing (from what I gather) the shutdown does, is doing what a normal Thread does once it&#39;s done. When the normal Thread will finish the run method of the Runnable(or Callable), it will be passed to Garbage Collection to be collected. With Executor Service the threads will simply be put on hold, they will not be ticked for the garbage collection. For that, the shutdown is needed.

Ok back to my question. Is there any reason to call shutdown on `ExecutorService` very often, or even right after submitting to it some tasks? I would like to leave behind the case someone is doing it and right after that calls to `awaitTermination()` as this is validated. Once we do that, we have to recreate a new `ExecutorService` all over again, to do the same thing. Isn&#39;t the whole idea for the `ExecutorService` to reuse the threads? So why destroy the `ExecutorService` so soon?

Isn&#39;t it a rational way to simply create `ExecutorService` (or couple depending on how many you need), then during the application running pass to them the tasks once they come along, and then on the application exit or some other important stages shutdown those executors?

I&#39;d like an answer from some experienced coders who do write a lot of asynchronous code using the ExecutorServices.

Second side question, a bit smaller deals with the android platform. IF some of you will say that it&#39;s not the best idea to shutdown executors every time, and your program on android, could you tell me how do you handle those shutdowns (to be specific - when you execute them) when we deal with different events of the application life cycle.

Because of the CommonsWare comment, I made the post neutral. I really am not interested in arguing about it to death and it seems it&#39;s leading there. I&#39;m only interested in learning about what I asked here from experienced developers if they are willing to share their experiences. Thanks.

Reason for calling shutdown() on ExecutorService

I am trying to run a SQL query to delete rows with id&#39;s 163 to 265 in a table

I tried this to delete less number of rows

        DELETE FROM `table` WHERE id IN (264, 265)
But when it comes to delete 100&#39;s of rows at a time, Is there any query similar to above method
I am also trying to use this kind of query but failed to execute it

        DELETE FROM `table` WHERE id IN (SELECT * FROM table WHERE id = )

Please tell me the query to do the above action...

How to delete multiple rows in SQL where id = (x to y)

I need to search an ObjectId with python using pymongo but I always get this error. Any ideas how to search? 


    import pymongo
    from pymongo import MongoClient
    from pymongo import ObjectId

    gate = collection.find({&#39;_id&#39;: ObjectId(modem[&quot;dis_imei&quot;])})
    print gate

        Traceback (most recent call last):
      File &quot;C:\Users\gerswin\Documents\Proyectos\Demonio py\test.py&quot;, line 2, in &lt;module&gt;
        import pymongo
      File &quot;C:\Python27\lib\site-packages\pymongo\__init__.py&quot;, line 80, in &lt;module&gt;
        from pymongo.connection import Connection
      File &quot;C:\Python27\lib\site-packages\pymongo\connection.py&quot;, line 39, in &lt;module&gt;
        from pymongo.mongo_client import MongoClient
      File &quot;C:\Python27\lib\site-packages\pymongo\mongo_client.py&quot;, line 45, in &lt;module&gt;
        from pymongo import (auth,
      File &quot;C:\Python27\lib\site-packages\pymongo\database.py&quot;, line 22, in &lt;module&gt;
        from pymongo.collection import Collection
      File &quot;C:\Python27\lib\site-packages\pymongo\collection.py&quot;, line 25, in &lt;module&gt;
        from pymongo.cursor import Cursor
      File &quot;C:\Python27\lib\site-packages\pymongo\cursor.py&quot;, line 19, in &lt;module&gt;
        from bson import RE_TYPE
    ImportError: cannot import name RE_TYPE

search by ObjectId in mongodb with pymongo

I need to search an ObjectId with python using pymongo but I always get this error. Any ideas how to search?
<pre><code class="hljs language-arduino">import pymongo
from pymongo import MongoClient
from pymongo import ObjectId

gate = collection.find({'_id': ObjectId(modem["dis_imei"])})
print gate

 Traceback (most recent call last):
 File "C:\Users\gerswin\Documents\Proyectos\Demonio py\test.py", line 2, in &#x3C;module>
 import pymongo
 File "C:\Python27\lib\site-packages\pymongo\__init__.py", line 80, in &#x3C;module>
 from pymongo.connection import Connection
 File "C:\Python27\lib\site-packages\pymongo\connection.py", line 39, in &#x3C;module>
 from pymongo.mongo_client import MongoClient
 File "C:\Python27\lib\site-packages\pymongo\mongo_client.py", line 45, in &#x3C;module>
 from pymongo import (auth,
 File "C:\Python27\lib\site-packages\pymongo\database.py", line 22, in &#x3C;module>
 from pymongo.collection import Collection
 File "C:\Python27\lib\site-packages\pymongo\collection.py", line 25, in &#x3C;module>
 from pymongo.cursor import Cursor
 File "C:\Python27\lib\site-packages\pymongo\cursor.py", line 19, in &#x3C;module>
 from bson import RE_TYPE
ImportError: cannot import name RE_TYPE
</code></pre>

I want to get both horizontal and vertical grid lines on my plot but only the horizontal grid lines are appearing by default. I am using a `pandas.DataFrame` from an sql query in python to generate a line plot with dates on the x-axis. I&#39;m not sure why they do not appear on the dates and I have tried to search for an answer to this but couldn&#39;t find one.

All I have used to plot the graph is the simple code below. 

    data.plot()
    grid(&#39;on&#39;)

data is the DataFrame which contains the dates and the data from the sql query. 

I have also tried adding the code below but I still get the same output with no vertical grid lines.

    ax = plt.axes()        
    ax.yaxis.grid() # horizontal lines
    ax.xaxis.grid() # vertical lines

Any suggestions?

![enter image description here][1]



  [1]: http://i.stack.imgur.com/nsdzO.png

Getting vertical gridlines to appear in line plot in matplotlib

I want to sort a list at first by a value and then by a second value. Is there an easy way to do this? Here is a small example:

    A = [{&#39;name&#39;:&#39;john&#39;,&#39;age&#39;:45},
         {&#39;name&#39;:&#39;andi&#39;,&#39;age&#39;:23},
         {&#39;name&#39;:&#39;john&#39;,&#39;age&#39;:22},
         {&#39;name&#39;:&#39;paul&#39;,&#39;age&#39;:35},
         {&#39;name&#39;:&#39;john&#39;,&#39;age&#39;:21}]

This command is for sorting this list by `&#39;name&#39;`:

    sorted(A, key = lambda user: user[&#39;name&#39;])

But how I can sort this list by a second value? Like `&#39;age&#39;` in this example.

I want a sorting like this (first sort by `&#39;name&#39;` and then sort by `&#39;age&#39;`):

    andi - 23
    john - 21
    john - 22
    john - 45
    paul - 35

Thanks!

Python: How to sort a list of dictionaries by several values?

I have a class, A, which is inherited by a bunch of other classes. Some of these have a few functions which are similar and it would be nice to have those functions defined somewhere else and called by the classes that need them. But those functions call functions defined in the super class.

    class A():
        def imp_func(*args):
            # called by the child class functions
    
    Class B(A):
        def common_func(self):
            # some stuff
            self.imp_func(*args)

So I have created my helper functions which take the `self object` as an argument and I can call the `imp_func` from inside the helper functions.

    def helper_func(obj, some_args):
        # some common stuff
        obj.imp_func(*args)
    
    class B(A):
        def common_func(self):
            # unique stuff
            helper_func(self, some_args)

This solves the problem.

But should I be doing this? Is this Pythonic? 

Is it okay to pass self to an external function

I have a markdown cell in iPython that contains four dollar signs. iPython interprets anything between dollar signs as a MathJax expression, which is not what I want. How do I escape the dollar signs? Escaping them with a backslash prevents MathJax from kicking in, but the backslash shows in the compiled Markdown.

ANy ideas on how to get just the dollar sign?

Thanks

Escaping dollar sign in ipython notebook

I have two files in two different directories, one is `&#39;/home/test/first/first.pdf&#39;`, the other is `&#39;/home/text/second/second.pdf&#39;`. I use following code to compress them:

    import zipfile, StringIO
    buffer = StringIO.StringIO()
    first_path = &#39;/home/test/first/first.pdf&#39;
    second_path = &#39;/home/text/second/second.pdf&#39;
    zip = zipfile.ZipFile(buffer, &#39;w&#39;)
    zip.write(first_path)
    zip.write(second_path)
    zip.close()

After I open the zip file that I created, I have a `home` folder in it, then there are two sub-folders in it, `first` and `second`, then the pdf files. I don&#39;t know how to include only two pdf files instead of having full path zipped into the zip archive. I hope I make my question clear, please help. 

How to eliminate absolute path in zip archive if absolute paths for files are provided?

Is it necessary to give &#39;worker&#39; information in Procfile? If yes then what it is actually? I have already added `web: node server/server.js` detail in the `Procfile`. 

What is Procfile? and Web and Worker

I have two collections.  The first collection contains students:

    { &quot;_id&quot; : ObjectId(&quot;51780f796ec4051a536015cf&quot;), &quot;name&quot; : &quot;John&quot; }
    { &quot;_id&quot; : ObjectId(&quot;51780f796ec4051a536015d0&quot;), &quot;name&quot; : &quot;Sam&quot; }
    { &quot;_id&quot; : ObjectId(&quot;51780f796ec4051a536015d1&quot;), &quot;name&quot; : &quot;Chris&quot; }
    { &quot;_id&quot; : ObjectId(&quot;51780f796ec4051a536015d2&quot;), &quot;name&quot; : &quot;Joe&quot; }

The second collection contains courses:

    {
            &quot;_id&quot; : ObjectId(&quot;51780fb5c9c41825e3e21fc4&quot;),
            &quot;name&quot; : &quot;CS 101&quot;,
            &quot;students&quot; : [
                    ObjectId(&quot;51780f796ec4051a536015cf&quot;),
                    ObjectId(&quot;51780f796ec4051a536015d0&quot;),
                    ObjectId(&quot;51780f796ec4051a536015d2&quot;)
            ]
    }
    {
            &quot;_id&quot; : ObjectId(&quot;51780fb5c9c41825e3e21fc5&quot;),
            &quot;name&quot; : &quot;Literature&quot;,
            &quot;students&quot; : [
                    ObjectId(&quot;51780f796ec4051a536015d0&quot;),
                    ObjectId(&quot;51780f796ec4051a536015d0&quot;),
                    ObjectId(&quot;51780f796ec4051a536015d2&quot;)
            ]
    }
    {
            &quot;_id&quot; : ObjectId(&quot;51780fb5c9c41825e3e21fc6&quot;),
            &quot;name&quot; : &quot;Physics&quot;,
            &quot;students&quot; : [
                    ObjectId(&quot;51780f796ec4051a536015cf&quot;),
                    ObjectId(&quot;51780f796ec4051a536015d0&quot;)
            ]
    }

Each course document contains `students` array which has a list of students registered for the course.  When a student views a course on a web page he needs to see if he has already registered for the course or not.  In order to do that, when the `courses` collection gets queried on the student&#39;s behalf, we need to find out if `students` array already contains the student&#39;s ObjectId.  Is there a way to specify in the projection of a find query to retrieve student `ObjectId` from `students` array only if it is there?

I tried to see if I could $elemMatch operator but it is geared towards an array of sub-documents.  I understand that I could use aggregation framework but it seems that it would be on overkill in this case.  Aggregation framework would probably not be as fast as a single find query.  Is there a way to query course collection to so that the returned document could be in a form similar to this?

    {
            &quot;_id&quot; : ObjectId(&quot;51780fb5c9c41825e3e21fc4&quot;),
            &quot;name&quot; : &quot;CS 101&quot;,
            &quot;students&quot; : [
                    ObjectId(&quot;51780f796ec4051a536015d0&quot;),
            ]
    }

MongoDB: How to find out if an array field contains an element?

What is the difference between save and insert in Mongo DB?
both looks the same 

    db.users.save({username:&quot;google&quot;,password:&quot;google123&quot;})

    db.users.insert({username:&quot;google&quot;,password:&quot;google123&quot;})

What is the difference between save and insert in Mongo DB?

I&#39;m trying to find all documents that do not contain at least one document with a specific field value.  For example here is a sample collection:

    {  _id : 1,
      docs : [
            { foo : 1,
              bar : 2},
            { foo : 3,
              bar : 3}
             ]
    },
    {  _id : 2,
      docs : [
            { foo : 2,
              bar : 2},
            { foo : 3,
              bar : 3}
             ]
    }

I want to find every record where there is not a document in the docs block that does not contain at least one record with foo = 1.  In the example above, only the second document should be returned.

I have tried the following, but it only tells me if there are any that don&#39;t match (which returns document 1.

    db.collection.find({&quot;docs&quot;: { $not: {$elemMatch: {foo: 1 } } } })

**UPDATE:** The query above actually does work. As many times happens, my data was wrong, not my code.

I have also looked at the [$nin operator][1] but the examples only show when the array contains a list of primitive values, not an additional document.  When I&#39;ve tried to do this with something like the following, it looks for the EXACT document rather than just the foo field I want.

    db.collection.find({&quot;docs&quot;: { $nin: {&#39;foo&#39;:1 } } })

Is there anyway to accomplish this with the basic operators?


  [1]: http://docs.mongodb.org/manual/reference/operator/nin/

Find documents with arrays not containing a document with a particular field value in MongoDB

I have a large amount of data in a collection in mongodb which I need to analyze. How do i import that data to pandas?

I am new to pandas and numpy.

EDIT:
The mongodb collection contains sensor values tagged with date and time. The sensor values are of float datatype. 


Sample Data:

    {
	&quot;_cls&quot; : &quot;SensorReport&quot;,
	&quot;_id&quot; : ObjectId(&quot;515a963b78f6a035d9fa531b&quot;),
	&quot;_types&quot; : [
		&quot;SensorReport&quot;
	],
	&quot;Readings&quot; : [
		{
			&quot;a&quot; : 0.958069536790466,
			&quot;_types&quot; : [
				&quot;Reading&quot;
			],
			&quot;ReadingUpdatedDate&quot; : ISODate(&quot;2013-04-02T08:26:35.297Z&quot;),
			&quot;b&quot; : 6.296118156595,
			&quot;_cls&quot; : &quot;Reading&quot;
		},
		{
			&quot;a&quot; : 0.95574014778624,
			&quot;_types&quot; : [
				&quot;Reading&quot;
			],
			&quot;ReadingUpdatedDate&quot; : ISODate(&quot;2013-04-02T08:27:09.963Z&quot;),
			&quot;b&quot; : 6.29651468650064,
			&quot;_cls&quot; : &quot;Reading&quot;
		},
		{
			&quot;a&quot; : 0.953648289182713,
			&quot;_types&quot; : [
				&quot;Reading&quot;
			],
			&quot;ReadingUpdatedDate&quot; : ISODate(&quot;2013-04-02T08:27:37.545Z&quot;),
			&quot;b&quot; : 7.29679823731148,
			&quot;_cls&quot; : &quot;Reading&quot;
		},
		{
			&quot;a&quot; : 0.955931884300997,
			&quot;_types&quot; : [
				&quot;Reading&quot;
			],
			&quot;ReadingUpdatedDate&quot; : ISODate(&quot;2013-04-02T08:28:21.369Z&quot;),
			&quot;b&quot; : 6.29642922525632,
			&quot;_cls&quot; : &quot;Reading&quot;
		},
		{
			&quot;a&quot; : 0.95821381,
			&quot;_types&quot; : [
				&quot;Reading&quot;
			],
			&quot;ReadingUpdatedDate&quot; : ISODate(&quot;2013-04-02T08:41:20.801Z&quot;),
			&quot;b&quot; : 7.28956613,
			&quot;_cls&quot; : &quot;Reading&quot;
		},
		{
			&quot;a&quot; : 4.95821335,
			&quot;_types&quot; : [
				&quot;Reading&quot;
			],
			&quot;ReadingUpdatedDate&quot; : ISODate(&quot;2013-04-02T08:41:36.931Z&quot;),
			&quot;b&quot; : 6.28956574,
			&quot;_cls&quot; : &quot;Reading&quot;
		},
		{
			&quot;a&quot; : 9.95821341,
			&quot;_types&quot; : [
				&quot;Reading&quot;
			],
			&quot;ReadingUpdatedDate&quot; : ISODate(&quot;2013-04-02T08:42:09.971Z&quot;),
			&quot;b&quot; : 0.28956488,
			&quot;_cls&quot; : &quot;Reading&quot;
		},
		{
			&quot;a&quot; : 1.95667927,
			&quot;_types&quot; : [
				&quot;Reading&quot;
			],
			&quot;ReadingUpdatedDate&quot; : ISODate(&quot;2013-04-02T08:43:55.463Z&quot;),
			&quot;b&quot; : 0.29115237,
			&quot;_cls&quot; : &quot;Reading&quot;
		}
	],
	&quot;latestReportTime&quot; : ISODate(&quot;2013-04-02T08:43:55.463Z&quot;),
	&quot;sensorName&quot; : &quot;56847890-0&quot;,
	&quot;reportCount&quot; : 8
    }

How to import data from mongodb to pandas?

I&#39;m doing a python script that writes some data to a mongodb.
I need to close the connection and free some resources, when finishing.

How is that done in Python?

How to close a mongodb python connection?

What is the quickest way to insert a pandas DataFrame into mongodb using `PyMongo`?

**Attempts**

    db.myCollection.insert(df.to_dict())

gave an error 

&gt; `InvalidDocument: documents must have only string keys, the key was
&gt; Timestamp(&#39;2013-11-23 13:31:00&#39;, tz=None)`
&gt; 

---
     db.myCollection.insert(df.to_json())

gave an error 

&gt; `TypeError: &#39;str&#39; object does not support item assignment`
&gt; 

---
     db.myCollection.insert({id: df.to_json()})

gave an error 

`InvalidDocument: documents must have only string a keys, key was &lt;built-in function id&gt;`

---
**df**

	&lt;class &#39;pandas.core.frame.DataFrame&#39;&gt;
	DatetimeIndex: 150 entries, 2013-11-23 13:31:26 to 2013-11-23 13:24:07
	Data columns (total 3 columns):
	amount    150  non-null values
	price     150  non-null values
	tid       150  non-null values
	dtypes: float64(2), int64(1)

Insert a Pandas Dataframe into mongodb using PyMongo

I can use the SQL `Like` Operator using `pymongo`,

    db.test.find({&#39;c&#39;:{&#39;$regex&#39;:&#39;ttt&#39;}})

But how can I use `Not Like` Operator?

I tried

    db.test.find({&#39;c&#39;:{&#39;$not&#39;:{&#39;$regex&#39;:&#39;ttt&#39;}})

but got error:

&gt; OperationFailure: $not cannot have a regex

How can I use &#39;Not Like&#39; operator in MongoDB

 I am trying to fetch some ids that exist in a mongo database with the following code:
  
    client = MongoClient(&#39;xx.xx.xx.xx&#39;, xxx)
    db = client.test_database
    db = client[&#39;...&#39;]
    collection = db.test_collection
    collection = db[&quot;...&quot;]


    for cursor in collection.find({ &quot;$and&quot; : [{ &quot;followers&quot; : { &quot;$gt&quot; : 2000 } }, { &quot;followers&quot; : { &quot;$lt&quot; : 3000 } }, { &quot;list_followers&quot; : { &quot;$exists&quot; : False } }] }): 
		print cursor[&#39;screenname&#39;]
		print cursor[&#39;_id&#39;][&#39;uid&#39;]
		id = cursor[&#39;_id&#39;][&#39;uid&#39;]


However, after a short while, I am receive this error: 

&gt;pymongo.errors.CursorNotFound: cursor id &#39;...&#39; not valid at server.

I found this [article][1] which refers to that problem. Nevertheless it is not clear to me which solution to take.  Is it possible to use `find().batch_size(30)`? What exactly does the above command do? Can I take all the database ids using `batch_size`?


  [1]: https://stackoverflow.com/questions/10298354/mongodb-cursor-id-not-valid-error

Content Type	Original Author	Original Content on Stackoverflow
Question	Gerswin Lee	View Question on Stackoverflow
Solution 1 - Python	Evgenii	View Answer on Stackoverflow

search by ObjectId in mongodb with pymongo

Python Problem Overview

Python Solutions

Solution 1 - Python

How to delete multiple rows in SQL where id = (x to y)

Reason for calling shutdown() on ExecutorService

Attributions