Initial migrations on a project can sometimes be troubleshot using --fake-initial

    python manage.py migrate --fake-initial

It&#39;s new in 1.8. In 1.7, --fake-initial was an implicit default, but explicit in 1.8.

From the Docs:

&gt; The --fake-initial option can be used to allow Django to skip an app’s initial migration if all database tables with the names of all models created by all CreateModel operations in that migration already exist. This option is intended for use when first running migrations against a database that preexisted the use of migrations. This option does not, however, check for matching database schema beyond matching table names and so is only safe to use if you are confident that your existing schema matches what is recorded in your initial migration.

https://docs.djangoproject.com/en/1.8/ref/django-admin/#django-admin-option---fake-initial

I solved this issue on Django 2.2.7 or Django 3.0 hosted on Ubuntu 18.04 + Postgres 10.10 version.

&gt; 1. Restore the database in Postgres database (used pgAdmin tool for this)
&gt; 2. (virtualenv)python manage.py loaddata dumpfile.json
&gt; 3. Dropping django_migrations table from database (used pgAdmin tool for this)
&gt; 4. (virtualenv)python manage.py makemigrations
&gt; 5. (virtualenv)python manage.py migrate --fake
&gt; 6. (virtualenv)python manage.py migrate
&gt; 7. (virtualenv)python manage.py collectstatic
&gt; 8. (virtualenv)python manage.py runserver 0.0.0.0:8000

I granted all privileges to the user on that specific database and it solved the issue.

I am using a toolbar as my actionbar in an activity.  I am trying to add the method `getActionBar().setDisplayHomeAsUpEnabled(true);` to the Activity.java file for Up navigation for older devices.

The method produces the following error message in Android Studio:

&gt; Method invocation may produce java.lang.NullPointerException

The Up navigation on the toolbar works fine on newer devices...now I&#39;m trying to figure out how to make sure it will work for older devices.
Please advise.

From build.gradle:

    dependencies {
       compile &quot;com.android.support:appcompat-v7:22.1.0&quot;
    }

From AndroidManifest.xml:

    android:theme=&quot;@style/Theme.AppCompat.NoActionBar.FullScreen&quot; 
    
From styles.xml

    &lt;style name=&quot;Theme.AppCompat.NoActionBar.FullScreen&quot; parent=&quot;AppTheme&quot;&gt;
    &lt;item name=&quot;android:windowNoTitle&quot;&gt;true&lt;/item&gt;
    &lt;item name=&quot;windowActionBar&quot;&gt;false&lt;/item&gt;
    &lt;item name=&quot;android:windowFullscreen&quot;&gt;true&lt;/item&gt;
    
from Activity.java

    public class CardViewActivity extends AppCompatActivity {

       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.cardviewinput);
        
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);

        if (toolbar != null) {
            // Up navigation to the parent activity for 4.0 and earlier
            getActionBar().setDisplayHomeAsUpEnabled(true);
            toolbar.setNavigationIcon(R.drawable.ic_action_previous_item);
            toolbar.setNavigationOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    onBackPressed();
                }
            });
        }

    }


How to fix getActionBar method may produce java.lang.NullPointerException

I am trying to build a web interface to Mock up a restful interface on networking device this networking device uses Digest Authentication and HTTPS.
I figured out how to integrate Digest Authentication into the web server but I cannot seem to find out how to get https using FLASK if you can show me how please comment on what i would need to do with the code below to make that happen.




    from flask import Flask, jsonify
    
    app = Flask(__name__)
    
    
    @app.route(&#39;/&#39;)
    def index():
        return &#39;Flask is running!&#39;
    
    
    @app.route(&#39;/data&#39;)
    def names():
        data = {&quot;names&quot;: [&quot;John&quot;, &quot;Jacob&quot;, &quot;Julie&quot;, &quot;Jennifer&quot;]}
        return jsonify(data)
    
    
    if __name__ == &#39;__main__&#39;:
        app.run()

can you add HTTPS functionality to a python flask web server?

After upgrading to django 1.8 I&#39;m recieving the error during migration:

    ProgrammingError: relation &quot;django_content_type&quot; already exists

I&#39;d be interested in the background behind this error, but more importantly,
How can I resolve it?

How can I resolve &#39;django_content_type already exists&#39;?

After upgrading to django 1.8 I'm recieving the error during migration:
<pre><code class="hljs language-arduino">ProgrammingError: relation "django_content_type" already exists
</code></pre>
I'd be interested in the background behind this error, but more importantly,
How can I resolve it?

I have a dataframe look like this:

    import pandas
    import numpy as np
    df = DataFrame(np.random.rand(4,4), columns = list(&#39;abcd&#39;))
    df
          a         b         c         d
    0  0.418762  0.042369  0.869203  0.972314
    1  0.991058  0.510228  0.594784  0.534366
    2  0.407472  0.259811  0.396664  0.894202
    3  0.726168  0.139531  0.324932  0.906575

How I can get all columns except `column b`?


How to select all columns, except one column in pandas?

I have a dataframe like this one:

    In [10]: df
    Out[10]: 
             Column 1
    foo              
    Apples          1
    Oranges         2
    Puppies         3
    Ducks           4

How to remove `index name` `foo` from that dataframe?
The desired output is like this:


    In [10]: df
    Out[10]: 
             Column 1             
    Apples          1
    Oranges         2
    Puppies         3
    Ducks           4

Remove index name in pandas

What does the following code do?

    a = lambda _:True

 

From what I read and tested in the interactive prompt, it seems to be a function that returns always `True`.

Am I understanding this correctly? I hope to understand why an underscore (`_`) was used as well. 


Python&#39;s lambda with underscore for an argument?

I am inserting JSON data into a MySQL database

I am parsing the JSON and then inserting it into a MySQL db using the python connector

Through trial, I can see the error is associated with this piece of code

    for steps in result[&#39;routes&#39;][0][&#39;legs&#39;][0][&#39;steps&#39;]:
        query = (&#39;SELECT leg_no FROM leg_data WHERE travel_mode = %s AND Orig_lat = %s AND Orig_lng = %s AND Dest_lat = %s AND Dest_lng = %s AND time_stamp = %s&#39;)
        if steps[&#39;travel_mode&#39;] == &quot;pub_tran&quot;:
            travel_mode = steps[&#39;travel_mode&#39;]
            Orig_lat = steps[&#39;var_1&#39;][&#39;dep&#39;][&#39;lat&#39;]
            Orig_lng = steps[&#39;var_1&#39;][&#39;dep&#39;][&#39;lng&#39;]
            Dest_lat = steps[&#39;var_1&#39;][&#39;arr&#39;][&#39;lat&#39;]
            Dest_lng = steps[&#39;var_1&#39;][&#39;arr&#39;][&#39;lng&#39;]
            time_stamp = leg[&#39;_sent_time_stamp&#39;] 
        if steps[&#39;travel_mode&#39;] ==&quot;a_pied&quot;:
            query = (&#39;SELECT leg_no FROM leg_data WHERE travel_mode = %s AND Orig_lat = %s AND Orig_lng = %s AND Dest_lat = %s AND Dest_lng = %s AND time_stamp = %s&#39;)
            travel_mode = steps[&#39;travel_mode&#39;]
            Orig_lat = steps[&#39;var_2&#39;][&#39;lat&#39;]
            Orig_lng = steps[&#39;var_2&#39;][&#39;lng&#39;]
            Dest_lat = steps[&#39;var_2&#39;][&#39;lat&#39;]
            Dest_lng = steps[&#39;var_2&#39;][&#39;lng&#39;]
            time_stamp = leg[&#39;_sent_time_stamp&#39;]
        cursor.execute(query,(travel_mode, Orig_lat, Orig_lng, Dest_lat, Dest_lng, time_stamp))
        leg_no = cursor.fetchone()[0]
        print(leg_no)

I have inserted higher level details and am now searching the database to associate this lower level information with its parent. The only way to find this unique value is to search via the origin and destination coordinates with the time_stamp. I believe the logic is sound and by printing the leg_no immediately after this section, I can see values which appear at first inspection to be correct

However, when added to the rest of the code, it causes subsequent sections where more data is inserted using the cursor to fail with this error - 


        raise errors.InternalError(&quot;Unread result found.&quot;)
    mysql.connector.errors.InternalError: Unread result found.

The issue seems similar to https://stackoverflow.com/questions/15336767/mysql-unread-result-with-python

Is the query too complex and needs splitting or is there another issue?

If the query is indeed too complex, can anyone advise how best to split this? 

EDIT As per @Gord&#39;s help, Ive tried to dump any unread results

    cursor.execute(query,(leg_travel_mode, leg_Orig_lat, leg_Orig_lng, leg_Dest_lat, leg_Dest_lng))
                leg_no = cursor.fetchone()[0]
                try:
                    cursor.fetchall()
                except mysql.connector.errors.InterfaceError as ie:
                    if ie.msg == &#39;No result set to fetch from.&#39;:
                        pass
                    else:
                        raise
                cursor.execute(query,(leg_travel_mode, leg_Orig_lat, leg_Orig_lng, leg_Dest_lat, leg_Dest_lng, time_stamp))

But, I still get 

    raise errors.InternalError(&quot;Unread result found.&quot;)
    mysql.connector.errors.InternalError: Unread result found.
    [Finished in 3.3s with exit code 1]

*scratches head*

EDIT 2 - when I print the ie.msg, I get - 

    No result set to fetch from



Python MySQL connector - unread result found when using fetchone

For some reason I cannot figure out why Django isn&#39;t handling my `request.body` content correctly.

It is being sent in `JSON` format, and looking at the `Network` tab in Dev Tools shows this as the request payload:

    {creator: &quot;creatorname&quot;, content: &quot;postcontent&quot;, date: &quot;04/21/2015&quot;}

which is exactly how I want it to be sent to my API.

In Django I have a view that accepts this request as a parameter and just for my testing purposes, should print `request.body[&quot;content&quot;]` to the console. 

Of course, nothing is being printed out, but when I print `request.body` I get this:

    b&#39;{&quot;creator&quot;:&quot;creatorname&quot;,&quot;content&quot;:&quot;postcontent&quot;,&quot;date&quot;:&quot;04/21/2015&quot;}&#39;

so I know that I *do* have a body being sent.

I&#39;ve tried using `json = json.loads(request.body)` to no avail either. Printing `json` after setting that variable also returns nothing.

Trying to parse `request.body` from POST in Django

I added a new, non-nullable field to my Django model and am trying to use migrations to deploy that change. How would I set default value to use for existing models to be some function of those models rather than a constant?

As an example let&#39;s say I previously had a `created_on` field and I just added an `updated_on` field whose value I want to set initially to the model&#39;s `created_on`. How would I do this in a migration?

This is what I am trying to start with:

        migrations.AddField(
            model_name=&#39;series&#39;,
            name=&#39;updated_as&#39;,
            field=models.DateTimeField(default=????, auto_now=True),
            preserve_default=False,
        ),

Django Migrations Add Field with Default as Function of Model

In Django, custom managers are a great way to organize reusable query logic. The [Django documentation on **Custom managers**][1] says:

&gt; There are two reasons you might want to customize a `Manager`: to add extra `Manager` methods, and/or to modify the initial `QuerySet` the `Manager` returns.

However, [it goes on to describe][2] how custom `QuerySet` classes can also be created, and that these can be made accessible directly from the data model as a manager using `QuerySet.as_manager()`:

&gt; The `Manager` instance created by `QuerySet.as_manager()` will be virtually identical to the `PersonManager` from the previous example.

It seems like there is a lot of flexibility in how one could organize their logic between custom `Manager` and/or custom `QuerySet` classes. What are the principles by which I should decide when to use one versus the other?


  [1]: https://docs.djangoproject.com/en/3.0/topics/db/managers/#custom-managers
  [2]: https://docs.djangoproject.com/en/3.0/topics/db/managers/#creating-a-manager-with-queryset-methods

When should I use a custom Manager versus a custom QuerySet in Django?

I&#39;m trying to set up the tables for a new django project (that is, the tables do NOT already exist in the database); the django version is 1.7 and the db back end is PostgreSQL. The name of the project is crud.  Results of migration attempt follow:


`python manage.py makemigrations crud`

    Migrations for &#39;crud&#39;:
      0001_initial.py:
        - Create model AddressPoint
        - Create model CrudPermission
        - Create model CrudUser
        - Create model LDAPGroup
        - Create model LogEntry
        - Add field ldap_groups to cruduser
        - Alter unique_together for crudpermission (1 constraint(s))

`python manage.py migrate crud`

    Operations to perform:
      Apply all migrations: crud
    Running migrations:
      Applying crud.0001_initial...Traceback (most recent call last):
      File &quot;manage.py&quot;, line 18, in &lt;module&gt;
        execute_from_command_line(sys.argv)
      File &quot;/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py&quot;, line 385, in execute_from_command_line
        utility.execute()
      File &quot;/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py&quot;, line 377, in execute
        self.fetch_command(subcommand).run_from_argv(self.argv)
      File &quot;/usr/local/lib/python2.7/dist-packages/django/core/management/base.py&quot;, line 288, in run_from_argv
        self.execute(*args, **options.__dict__)
      File &quot;/usr/local/lib/python2.7/dist-packages/django/core/management/base.py&quot;, line 338, in execute
        output = self.handle(*args, **options)
      File &quot;/usr/local/lib/python2.7/dist-packages/django/core/management/commands/migrate.py&quot;, line 161, in handle
        executor.migrate(targets, plan, fake=options.get(&quot;fake&quot;, False))
      File &quot;/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py&quot;, line 68, in migrate
        self.apply_migration(migration, fake=fake)
      File &quot;/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py&quot;, line 102, in apply_migration
        migration.apply(project_state, schema_editor)
      File &quot;/usr/local/lib/python2.7/dist-packages/django/db/migrations/migration.py&quot;, line 108, in apply
        operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
      File &quot;/usr/local/lib/python2.7/dist-packages/django/db/migrations/operations/models.py&quot;, line 36, in database_forwards
        schema_editor.create_model(model)
      File &quot;/usr/local/lib/python2.7/dist-packages/django/db/backends/schema.py&quot;, line 262, in create_model
        self.execute(sql, params)
      File &quot;/usr/local/lib/python2.7/dist-packages/django/db/backends/schema.py&quot;, line 103, in execute
        cursor.execute(sql, params)
      File &quot;/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py&quot;, line 82, in execute
        return super(CursorDebugWrapper, self).execute(sql, params)
      File &quot;/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py&quot;, line 66, in execute
        return self.cursor.execute(sql, params)
      File &quot;/usr/local/lib/python2.7/dist-packages/django/db/utils.py&quot;, line 94, in __exit__
        six.reraise(dj_exc_type, dj_exc_value, traceback)
      File &quot;/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py&quot;, line 66, in execute
        return self.cursor.execute(sql, params)
    django.db.utils.ProgrammingError: relation &quot;crud_crudpermission&quot; already exists


Some highlights from the migration file:

    dependencies = [
        (&#39;auth&#39;, &#39;0001_initial&#39;),
        (&#39;contenttypes&#39;, &#39;0001_initial&#39;),
    ]
        migrations.CreateModel(
            name=&#39;CrudPermission&#39;,
            fields=[
                (&#39;id&#39;, models.AutoField(verbose_name=&#39;ID&#39;, serialize=False, auto_created=True, primary_key=True)),
                (&#39;_created_by&#39;, models.CharField(default=b&#39;&#39;, max_length=64, null=True, editable=False, blank=True)),
                (&#39;_last_updated_by&#39;, models.CharField(default=b&#39;&#39;, max_length=64, null=True, editable=False, blank=True)),
                (&#39;_created&#39;, models.DateTimeField(null=True, editable=False, blank=True)),
                (&#39;_last_updated&#39;, models.DateTimeField(null=True, editable=False, blank=True)),
                (&#39;domain&#39;, models.CharField(max_length=32, choices=[(b&#39;town&#39;, b&#39;Town&#39;), (b&#39;boe&#39;, b&#39;BOE&#39;), (b&#39;police&#39;, b&#39;Police&#39;)])),
                (&#39;ldap_group&#39;, models.CharField(max_length=128, verbose_name=b&#39;LDAP group&#39;)),
                (&#39;can_add&#39;, models.BooleanField(default=False, verbose_name=b&#39;add&#39;)),
                (&#39;can_change&#39;, models.BooleanField(default=False, verbose_name=b&#39;change&#39;)),
                (&#39;restrict_change_to_own&#39;, models.BooleanField(default=False)),
                (&#39;can_delete&#39;, models.BooleanField(default=False, verbose_name=b&#39;delete&#39;)),
                (&#39;restrict_delete_to_own&#39;, models.BooleanField(default=False)),
                (&#39;models&#39;, models.ManyToManyField(to=&#39;contenttypes.ContentType&#39;, null=True, blank=True)),
            ],
            options={
                &#39;verbose_name&#39;: &#39;CRUD permission&#39;,
            },
            bases=(models.Model,),
        ),
        migrations.AlterUniqueTogether(
            name=&#39;crudpermission&#39;,
            unique_together=set([(&#39;ldap_group&#39;, &#39;can_add&#39;, &#39;can_change&#39;, &#39;can_delete&#39;, &#39;domain&#39;)]),
        )

,


The crud app is not meant to actually do anything, but I use it another app, so when I try migrate from that app, I trigger the above problem.

I&#39;ve found other examples on the web of people with similar issues, but none of their cases seem to apply because

 1. The problem affects an entire relation, not just one column
 2. I am not using multiple inheritance.

Where should I look next to find the underlying problem?

django.db.utils.ProgrammingError: relation already exists

this is a simple question. I&#39;d like to know if it is the same to write:

    queryset = Model.objects.filter(field=None)

than:

    queryset = Model.objects.filter(field__isnull=True)

I&#39;m using django 1.8

Content Type	Original Author	Original Content on Stackoverflow
Question	Dan O'Boyle	View Question on Stackoverflow
Solution 1 - Python	Dan O'Boyle	View Answer on Stackoverflow
Solution 2 - Python	Santana	View Answer on Stackoverflow
Solution 3 - Python	adriaanbd	View Answer on Stackoverflow

How can I resolve 'django_content_type already exists'?

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can you add HTTPS functionality to a python flask web server?

How to fix getActionBar method may produce java.lang.NullPointerException

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