The [`filter_by()`][1] method takes a sequence of keyword arguments, so you always have to use `=` with it.

You want to use the [`filter()`][2] method which allows for `!=`:

    seats = Seat.query.filter(Seat.invite != None).all()



  [1]: https://docs.sqlalchemy.org/en/latest/orm/query.html#sqlalchemy.orm.query.Query.filter_by
  [2]: https://docs.sqlalchemy.org/en/latest/orm/query.html#sqlalchemy.orm.query.Query.filter

I think this can help
http://docs.sqlalchemy.org/en/rel_0_9/core/sqlelement.html#sqlalchemy.sql.operators.ColumnOperators.isnot
&lt;br&gt;
# Is None
    query.filter(User.name == None)
or alternatively, if pep8/linters are a concern&lt;br&gt;&lt;br&gt;
    `query.filter(User.name.is_(None))`
&lt;br&gt;
&lt;br&gt;
# Is not None
    query.filter(User.name != None)

or alternatively, if pep8/linters are a concern
&lt;br&gt;&lt;br&gt;
`query.filter(User.name.isnot(None))`

I have below code in c# 4.0.

    //Dictionary object with Key as string and Value as List of Component type object
    Dictionary&lt;String, List&lt;Component&gt;&gt; dic = new Dictionary&lt;String, List&lt;Component&gt;&gt;();
    
    //Here I am trying to do the loping for List&lt;Component&gt;
    foreach (List&lt;Component&gt; lstComp in dic.Values.ToList())
    {
    	// Below I am trying to get first component from the lstComp object.
        // Can we achieve same thing using LINQ?
        // Which one will give more performance as well as good object handling?
    	Component depCountry = lstComp[0].ComponentValue(&quot;Dep&quot;);
    }



How to get first object out from List&lt;Object&gt; using Linq

As the title of this question suggests I&#39;m wanting to set max disk/memory and cpu usage for a container using docker (docker.io).

Is there a way to do this using just docker?

How do I set resources allocated to a container using docker?

I can query my `Seat` table for all seats where there is no invite assigned:

    seats = Seat.query.filter_by(invite=None).all()

However, when querying for all seats that have an invite assigned, I get a `NameError`:

    seats = Seat.query.filter_by(invite!=None).all()

&lt;!-- language: lang-none --&gt;

    NameError: name &#39;invite&#39; is not defined

Here is my `Seat` class:

    class Seat(db.Model):
        id = db.Column(db.Integer, primary_key=True)

        invite_id = db.Column(db.Integer, db.ForeignKey(&#39;invite.id&#39;))
        invite = db.relationship(&#39;Invite&#39;,
            backref=db.backref(&#39;folks&#39;, lazy=&#39;dynamic&#39;))

How can I query for all seats where the owner is not blank?

Flask SQLAlchemy querying a column with &quot;not equals&quot;

I can query my <code>Seat</code> table for all seats where there is no invite assigned:
<pre><code class="hljs language-ini">seats = Seat.query.filter_by(invite=None).all()
</code></pre>
However, when querying for all seats that have an invite assigned, I get a <code>NameError</code>:
<pre><code class="hljs language-ini">seats = Seat.query.filter_by(invite!=None).all()
</code></pre>

<pre><code class="hljs language-csharp">NameError: name 'invite' is not defined
</code></pre>
Here is my <code>Seat</code> class:
<pre><code class="hljs language-ini">class Seat(db.Model):
 id = db.Column(db.Integer, primary_key=True)

 invite_id = db.Column(db.Integer, db.ForeignKey('invite.id'))
 invite = db.relationship('Invite',
 backref=db.backref('folks', lazy='dynamic'))
</code></pre>
How can I query for all seats where the owner is not blank?

    &gt;&gt;&gt; ex=np.arange(30)
    &gt;&gt;&gt; e=np.reshape(ex,[3,10])
    &gt;&gt;&gt; e
    array([[ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9],
           [10, 11, 12, 13, 14, 15, 16, 17, 18, 19],
           [20, 21, 22, 23, 24, 25, 26, 27, 28, 29]])
    &gt;&gt;&gt; e&gt;15
    array([[False, False, False, False, False, False, False, False, False,
            False],
           [False, False, False, False, False, False,  True,  True,  True,
             True],
           [ True,  True,  True,  True,  True,  True,  True,  True,  True,
             True]], dtype=bool)


I need to find the rows that have true or rows in `e` whose value are more than 15. I could iterate using a for loop, however, I would like to know if there is a way numpy could do this more efficiently?

numpy get index where value is true

I am curious as to why `df[2]` is not supported, while `df.ix[2]` and `df[2:3]` both work. 

    In [26]: df.ix[2]
    Out[26]: 
    A    1.027680
    B    1.514210
    C   -1.466963
    D   -0.162339
    Name: 2000-01-03 00:00:00
    
    In [27]: df[2:3]
    Out[27]: 
                      A        B         C         D
    2000-01-03  1.02768  1.51421 -1.466963 -0.162339

I would expect `df[2]` to work the same way as `df[2:3]` to be consistent with Python indexing convention. Is there a design reason for not supporting indexing row by single integer?

Selecting a row of pandas series/dataframe by integer index

[This was my source I started with.][1]

My List 


    L = [0, 23, 234, 89, None, 0, 35, 9]

When I run this :

    L = filter(None, L)

I get this results 

    [23, 234, 89, 35, 9]

But this is not what I need, what I really need is :

    [0, 23, 234, 89, 0, 35, 9]


Because I&#39;m calculating percentile of the data and the 0 make a lot of difference.

How to remove the None value from a list without removing 0 value?

  [1]: http://docs.python.org/2/library/functions.html#filter

remove None value from a list without removing the 0 value

I have a dataframe in pandas called &#39;munged_data&#39; with two columns &#39;entry_date&#39; and &#39;dob&#39; which i have converted to Timestamps using pd.to_timestamp.I am trying to figure out how to calculate ages of people based on the time difference between &#39;entry_date&#39; and &#39;dob&#39; and to do this i need to get the difference in days between the two columns ( so that i can then do somehting like round(days/365.25). I do not seem to be able to find a way to do this using a vectorized operation. When I do munged_data.entry_date-munged_data.dob i get the following : 

    internal_quote_id
    2                    15685977 days, 23:54:30.457856
    3                    11651985 days, 23:49:15.359744
    4                     9491988 days, 23:39:55.621376
    7                     11907004 days, 0:10:30.196224
    9                    15282164 days, 23:30:30.196224
    15                  15282227 days, 23:50:40.261632  

However i do not seem to be able to extract the days as an integer so that i can continue with my calculation. 
Any help appreciated.

Pandas Timedelta in Days

I&#39;m just playing around learning classes functions etc, So I decided to create a simple function what should give me tax amount.

this is my code so far.

  

    class VAT_calculator:
        &quot;&quot;&quot;
         A set of methods for VAT calculations.
        &quot;&quot;&quot;
    
        def __init__(self, amount=None):
            self.amount = amount
            self.VAT = decimal.Decimal(&#39;0.095&#39;)
    
        def initialize(self):
            self.amount = 0
    
        def total_with_VAT(self):
            &quot;&quot;&quot;
            Returns amount with VAT added.
            &quot;&quot;&quot;
            if not self.amount:
                msg = u&quot;Cannot add VAT if no amount is passed!&#39;&quot;
                raise ValidationError(msg)
    
            return (self.amount * self.VAT).quantize(self.amount, rounding=decimal.ROUND_UP)


My issue is I&#39;m getting the following error:

&gt;unsupported operand type(s) for *: &#39;float&#39; and &#39;Decimal&#39;**

I don&#39;t see why this should not work!
 

unsupported operand type(s) for *: &#39;float&#39; and &#39;Decimal&#39;

I&#39;m working on forum template using Flask. When I attempt creating a new thread in the browser using forms, SQLAlchemy throws an AttributeError. The problem showed up when I tried implementing a one-to-many relationship with Forum-to-Thread and a one-to-many relationship with Thread-to-User.

models.py

    class User(db.Model):
      id = db.Column(db.Integer, primary_key=True)
      username = db.Column(db.String(32), index=True, unique=True)
      password = db.Column(db.String(32), index=True)
      email = db.Column(db.String(120), index=True, unique=True)
      role = db.Column(db.SmallInteger, default=ROLE_USER)
    
      posts = db.relationship(&#39;Post&#39;, backref=&#39;author&#39;, lazy=&#39;dynamic&#39;)

    class Forum(db.Model):
      id = db.Column(db.Integer, primary_key=True)
      title = db.Column(db.String(128))
      description = db.Column(db.Text)
    
      threads = db.relationship(&#39;Thread&#39;, backref=&#39;forum&#39;, lazy=&#39;dynamic&#39;)
    	  
    class Thread(db.Model):
      
      id = db.Column(db.Integer, primary_key=True)
      title = db.Column(db.String(128))
      author= db.Column(db.String(32))
      timestamp = db.Column(db.DateTime)
      forum_id = db.Column(db.Integer, db.ForeignKey(&#39;forum.id&#39;))
    
      posts = db.relationship(&#39;Post&#39;, backref=&#39;thread&#39;, lazy=&#39;dynamic&#39;)
    	
    class Post(db.Model):
      
      id = db.Column(db.Integer, primary_key=True)
      body = db.Column(db.Text)
      timestamp = db.Column(db.DateTime)
      thread_id = db.Column(db.Integer, db.ForeignKey(&#39;thread.id&#39;))
      user_id = db.Column(db.Integer, db.ForeignKey(&#39;user.id&#39;))

All the new posts/threads and handled within views.py

views.py

    @app.route(&#39;/forum/id=&lt;id&gt;/submit&#39;, methods=[&#39;GET&#39;,&#39;POST&#39;])
    @login_required
    def new_thread(id):
      form = ThreadForm()
      forum = Forum.query.filter_by(id=id).first()
      if form.validate_on_submit():
        thread = Thread(title=form.title.data,
                        author=g.user.username,
                        timestamp=datetime.utcnow())
        db.session.add(thread)
        db.session.flush()
        post = Post(body=form.body.data,
                    timestamp=datetime.utcnow(),
                    thread=thread.id,
                    author=g.user.id)
        db.session.add(post)
        db.session.commit()
        flash(&#39;Post successful.&#39;)
        return redirect(url_for(&#39;forum_index&#39;, id=id))
      return render_template(&#39;forum/thread_submit.html&#39;, title=forum.title, form=form) 

AttributeError: &#39;int&#39; object has no attribute &#39;_sa_instance_state&#39;

I&#39;m following the flask-sqlalchemy tutorial on [declaring models][1] regarding one-to-many relationship. The example code is as follows:

    class Person(db.Model):
        id = db.Column(db.Integer, primary_key=True)
        name = db.Column(db.String(50))
        addresses = db.relationship(&#39;Address&#39;, backref=&#39;person&#39;,
                                    lazy=&#39;dynamic&#39;)
    
    class Address(db.Model):
        id = db.Column(db.Integer, primary_key=True)
        email = db.Column(db.String(50))
        person_id = db.Column(db.Integer, db.ForeignKey(&#39;person.id&#39;))

Now I&#39;m wondering how to insert new records into DB using such model. I assume I need a constructor __init__, but I have difficulties to understand how it should be implemented and used. The main problem for me here is that Person depends on Address and Address has ForeignKey to Person, so it should know about the Person in advance.

Plase help me to understand how it should be performed.

Thank you in advance.

  [1]: http://flask-sqlalchemy.pocoo.org/2.1/models/

Inserting new records with one-to-many relationship in sqlalchemy

How to make `SQLAlchemy` in `Tornado` to be `async` ?
I found example for MongoDB on [async mongo example][1] but I couldn&#39;t find anything like `motor` for `SQLAlchemy`. Does anyone know how to make `SQLAlchemy` queries to execute with `tornado.gen` ( I am using `MySQL` below `SQLAlchemy`, at the moment my handlers reads from database and return result, I would like to make this async).


  [1]: http://emptysquare.net/blog/refactoring-tornado-code-with-gen-engine/

How to make SQLAlchemy in Tornado to be async?

I&#39;m using Flask-SQLAlchemy to query from a database of users; however, while

    user = models.User.query.filter_by(username=&quot;ganye&quot;).first()

will return

    &lt;User u&#39;ganye&#39;&gt;

doing

    user = models.User.query.filter_by(username=&quot;GANYE&quot;).first()

returns

    None

I&#39;m wondering if there&#39;s a way to query the database in a case insensitive way, so that the second example will still return

    &lt;User u&#39;ganye&#39;&gt;

Case Insensitive Flask-SQLAlchemy Query

How do I delete all rows in a single table using Flask-SQLAlchemy?

Looking for something like this: 

    &gt;&gt;&gt; users = models.User.query.all()
    &gt;&gt;&gt; models.db.session.delete(users)
    
    # but it errs out: UnmappedInstanceError: Class &#39;__builtin__.list&#39; is not mapped

Flask-SQLAlchemy how to delete all rows in a single table

Method One: Using special g object from http://flask.pocoo.org/docs/tutorial/dbcon/ and http://flask.pocoo.org/docs/patterns/sqlite3/

    import sqlite3
    from flask import g
    
    DATABASE = &#39;/path/to/database.db&#39;
    
    def connect_db():
        return sqlite3.connect(DATABASE)
    
    @app.before_request
    def before_request():
        g.db = connect_db()
    
    @app.teardown_request
    def teardown_request(exception):
        if hasattr(g, &#39;db&#39;):
            g.db.close()

Method Two: Using Mysterious _app_ctx_stack from https://github.com/mitsuhiko/flask/blob/master/examples/flaskr/flaskr.py

    from sqlite3 import dbapi2 as sqlite3
    from flask import Flask, request, session, g, redirect, url_for, abort, \
         render_template, flash, _app_ctx_stack
    def get_db():
        &quot;&quot;&quot;Opens a new database connection if there is none yet for the
        current application context.
        &quot;&quot;&quot;
        top = _app_ctx_stack.top
        if not hasattr(top, &#39;sqlite_db&#39;):
            top.sqlite_db = sqlite3.connect(app.config[&#39;DATABASE&#39;])
        return top.sqlite_db
    
    
    @app.teardown_appcontext
    def close_db_connection(exception):
        &quot;&quot;&quot;Closes the database again at the end of the request.&quot;&quot;&quot;
        top = _app_ctx_stack.top
        if hasattr(top, &#39;sqlite_db&#39;):
            top.sqlite_db.close()

Which method is better? What is the difference?

Connect to a Database in Flask, Which Approach is better?

I&#39;m investigating how to develop a decent web app with Python. Since I don&#39;t want some high-order structures to get in my way, my choice fell on the lightweight [Flask framework][1]. Time will tell if this was the right choice.

So, now I&#39;ve set up an Apache server with mod_wsgi, and my test site is running fine. However, I&#39;d like to speed up the development routine by making the site automatically reload upon any changes in py or template files I make. I see that any changes in site&#39;s .wsgi file causes reloading (even without WSGIScriptReloading On in the apache config file), but I still have to prod it manually (ie, insert extra linebreak, save). Is there some way how to cause reload when I edit some of the app&#39;s py files? Or, I am expected to use IDE that refreshes the .wsgi file for me?


  [1]: https://flask.palletsprojects.com/en/1.1.x/

Auto reloading python Flask app upon code changes

How do you use `url_for` in Flask to reference a file in a folder?  For example, I have some static files in the `static` folder, some of which may be in subfolders such as `static/bootstrap`.

When I try to serve a file from `static/bootstrap`, I get an error.

     &lt;link rel=stylesheet type=text/css href=&quot;{{ url_for(&#39;static/bootstrap&#39;, filename=&#39;bootstrap.min.css&#39;) }}&quot;&gt;

I can reference files that aren&#39;t in subfolders with this, which works.

     &lt;link rel=stylesheet type=text/css href=&quot;{{ url_for(&#39;static&#39;, filename=&#39;bootstrap.min.css&#39;) }}&quot;&gt;

What is the correct way to reference static files with `url_for`?  How do I use `url_for` to generate urls to static files at any level?

Link to Flask static files with url_for

My response back from MongoDB after querying an aggregated function on document using Python, It returns valid response and i can print it but can not return it.

Error: 

    TypeError: ObjectId(&#39;51948e86c25f4b1d1c0d303c&#39;) is not JSON serializable

Print:

    {&#39;result&#39;: [{&#39;_id&#39;: ObjectId(&#39;51948e86c25f4b1d1c0d303c&#39;), &#39;api_calls_with_key&#39;: 4, &#39;api_calls_per_day&#39;: 0.375, &#39;api_calls_total&#39;: 6, &#39;api_calls_without_key&#39;: 2}], &#39;ok&#39;: 1.0}

But When i try to return:

    TypeError: ObjectId(&#39;51948e86c25f4b1d1c0d303c&#39;) is not JSON serializable

It is RESTfull call:

    @appv1.route(&#39;/v1/analytics&#39;)
    def get_api_analytics():
        # get handle to collections in MongoDB
        statistics = sldb.statistics
    
        objectid = ObjectId(&quot;51948e86c25f4b1d1c0d303c&quot;)
    
        analytics = statistics.aggregate([
        {&#39;$match&#39;: {&#39;owner&#39;: objectid}},
        {&#39;$project&#39;: {&#39;owner&#39;: &quot;$owner&quot;,
        &#39;api_calls_with_key&#39;: {&#39;$cond&#39;: [{&#39;$eq&#39;: [&quot;$apikey&quot;, None]}, 0, 1]},
        &#39;api_calls_without_key&#39;: {&#39;$cond&#39;: [{&#39;$ne&#39;: [&quot;$apikey&quot;, None]}, 0, 1]}
        }},
        {&#39;$group&#39;: {&#39;_id&#39;: &quot;$owner&quot;,
        &#39;api_calls_with_key&#39;: {&#39;$sum&#39;: &quot;$api_calls_with_key&quot;},
        &#39;api_calls_without_key&#39;: {&#39;$sum&#39;: &quot;$api_calls_without_key&quot;}
        }},
        {&#39;$project&#39;: {&#39;api_calls_with_key&#39;: &quot;$api_calls_with_key&quot;,
        &#39;api_calls_without_key&#39;: &quot;$api_calls_without_key&quot;,
        &#39;api_calls_total&#39;: {&#39;$add&#39;: [&quot;$api_calls_with_key&quot;, &quot;$api_calls_without_key&quot;]},
        &#39;api_calls_per_day&#39;: {&#39;$divide&#39;: [{&#39;$add&#39;: [&quot;$api_calls_with_key&quot;, &quot;$api_calls_without_key&quot;]}, {&#39;$dayOfMonth&#39;: datetime.now()}]},
        }}
        ])
    
    
        print(analytics)
    
        return analytics

db is well connected and collection is there too and I got back valid expected result but when i try to return it gives me Json error. Any idea how to convert the response back into JSON. Thanks

TypeError: ObjectId(&#39;&#39;) is not JSON serializable

I already have an existing Database that has a lot of tables and a lot of data in `MySQL`. I intend to create a `Flask` app and use sqlalchemy along with it. Now I asked out on irc and looked around on google and tried the following ideas:

**First** I used [sqlacodegen][1] to generate the models from my `DB`. But then I was confused about it a little and looked some more. And I found [this][2].

This looked like an elegant solution.

So **Second**, I rewrote my `models.py` according to the solution there and now I am even more confused. I am looking for the best approach to build this flask app along with the already existing DB. 

I looked into the flask documentation but didnt really get any help for a project with an already existing db. There is a lot of good stuff for creating something from scratch, creating the db and all. But I am really confused.

Please Note that its my first day with `Flask`, but I have experience with `Django`, so the basic concepts are not a hurdle. I need some guidance in choosing the best approach for this usecase. A detailed explanation would be greatly appreciated. By detailed I definitely do not expect someone to write all the code and spoon feed me on this, but just enough to get me started, that is integrate this db seamlessly into `flask` via `sqlalchemy`. Note my DB is in `MySQL`.


  [1]: https://pypi.python.org/pypi/sqlacodegen
  [2]: http://flask.pocoo.org/mailinglist/archive/2012/5/23/flask-sqlalchemy-with-pre-existing-database/#9974419419ee1960c88c98689f6aee9d

Content Type	Original Author	Original Content on Stackoverflow
Question	SeanPlusPlus	View Question on Stackoverflow
Solution 1 - Python	Nathan Villaescusa	View Answer on Stackoverflow
Solution 2 - Python	bull90	View Answer on Stackoverflow

Flask SQLAlchemy querying a column with "not equals"

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

Is None

Is not None

How do I set resources allocated to a container using docker?

How to get first object out from List<Object> using Linq

Attributions