    if test.sound.name: 
         print &quot;I have a sound file&quot;
    else:   
         print &quot;no sound&quot;

Also, `FileField`&#39;s boolean value will be False when there&#39;s no file: `bool(test.sound) == False` when `test.sound.name` is falsy.

According to this [answer][1] from a different question, you can try this:


    class MyModel(models.Model):
      name = models.CharField(max_length=50)
      sound = models.FileField(upload_to=&#39;audio/&#39;, blank=True)
    
    def __nonzero__(self):
        return bool(self.sound)


  [1]: https://stackoverflow.com/a/5213095/9785224

I made changes to a lot of files, and in the meantime I figured I rather commit this untested code to a yet-to-be-created branch, so that users of the existing code base are not affected.

As I touched really many, many files and created and added new sub-projects etc., I want to avoid copying files and folders manually.

What&#39;s the easiest way to get this done in Visual Studio?

TFS: submit changes done locally in one branch to another branch

I&#39;m new to Javascript and was reading up on it, when I came to a chapter that described function recursion.  It used an example function to find the nth number of the Fibonacci sequence.  The code is as follows:

```js
function fibonacci(n) {
    if (n &lt; 2){
        return 1;
    }else{
	    return fibonacci(n-2) + fibonacci(n-1);
    }
}

console.log(fibonacci(7));
//Returns 21
```
I&#39;m having trouble grasping exactly what this function is doing.  Can someone explain what&#39;s going on here?  I&#39;m getting stuck on the 5th line, where the function calls itself.  What&#39;s happening here?

How does the fibonacci recursive function &quot;work&quot;?

I have a model with an optional file field

    class MyModel(models.Model):
      name = models.CharField(max_length=50)
      sound = models.FileField(upload_to=&#39;audio/&#39;, blank=True)

---
Let&#39;s put a value

    &gt;&gt;&gt; test = MyModel(name=&#39;machin&#39;)
    &gt;&gt;&gt; test.save()

---
Why do I get that ?

    &gt;&gt;&gt; test.sound
    &lt;FieldFile: None&gt;
    &gt;&gt;&gt; test.sound is None
    False

---
How can I check if there is a file set ?  


Django - FileField check if None

I have a model with an optional file field
<pre><code class="hljs language-ini">class MyModel(models.Model):
 name = models.CharField(max_length=50)
 sound = models.FileField(upload_to='audio/', blank=True)
</code></pre>
<hr>
Let's put a value
<pre><code class="hljs language-python-repl">>>> test = MyModel(name='machin')
>>> test.save()
</code></pre>
<hr>
Why do I get that ?
<pre><code class="hljs language-python">>>> test.sound
&#x3C;FieldFile: None>
>>> test.sound is None
False
</code></pre>
<hr>
How can I check if there is a file set ?

Why does [PEP 8 recommend not having spaces around `=` in a keyword argument or a default parameter value][1]?

Is this inconsistent with recommending spaces around every other occurrence of `=` in Python code?

How is:
    
    func(1, 2, very_long_variable_name=another_very_long_variable_name)

better than:

    func(1, 2, very_long_variable_name = another_very_long_variable_name)

Any links to discussion/explanation by Python&#39;s [BDFL](http://en.wikipedia.org/wiki/Benevolent_Dictator_for_Life) will be appreciated.

Mind, this question is more about kwargs than default values, i just used the phrasing from PEP 8.

I&#39;m not soliciting opinions. I&#39;m asking for reasons behind this decision. It&#39;s more like asking **why** would I use `{` on the same line as `if` statement in a C program, not **whether** I should use it or not.


  [1]: http://www.python.org/dev/peps/pep-0008/#other-recommendations

PEP 8, why no spaces around &#39;=&#39; in keyword argument or a default parameter value?

I&#39;m Java person who just started learning Python. Take this example:
   
    class Person():
        def __init__(self, name, phone):
            self.name = name
            self.phone = phone

    class Teenager(Person):
        def __init__(self, name, phone, website):
            self.name=name
            self.phone=phone
            self.website=website

I&#39;m sure there&#39;s a lot of redundant code (I know in Java, there are a lot of redundancies for the bit of code above). 

Which parts are redundant with respect to which attributes are already inherited from the parent class?      
 

The inheritance of attributes using __init__

I&#39;ve got an `ndarray` in python with a `dtype` of `float64`. I&#39;d like to convert the array to be an array of integers. How should I do this?

`int()` won&#39;t work, as it says it can&#39;t convert it to a scalar. Changing the `dtype` field itself obviously doesn&#39;t work, as the actual bytes haven&#39;t changed. I can&#39;t seem to find anything on Google or in the documentation - what&#39;s the best way to do this?

Convert ndarray from float64 to integer

After much searching I couldn&#39;t find out how to use smtplib.sendmail to send to multiple recipients.  The problem was every time the mail would be sent the mail headers would appear to contain multiple addresses, but in fact only the first recipient would receive the email.

The problem seems to be that the [`email.Message`][1] module expects something different than the [`smtplib.sendmail()`][2] function.

In short, to send to multiple recipients you should set the header to be a string of comma delimited email addresses.  The `sendmail()` parameter `to_addrs` however should be a list of email addresses.

    from email.MIMEMultipart import MIMEMultipart
    from email.MIMEText import MIMEText
    import smtplib

    msg = MIMEMultipart()
    msg[&quot;Subject&quot;] = &quot;Example&quot;
    msg[&quot;From&quot;] = &quot;me@example.com&quot;
    msg[&quot;To&quot;] = &quot;malcom@example.com,reynolds@example.com,firefly@example.com&quot;
    msg[&quot;Cc&quot;] = &quot;serenity@example.com,inara@example.com&quot;
    body = MIMEText(&quot;example email body&quot;)
    msg.attach(body)
    smtp = smtplib.SMTP(&quot;mailhost.example.com&quot;, 25)
    smtp.sendmail(msg[&quot;From&quot;], msg[&quot;To&quot;].split(&quot;,&quot;) + msg[&quot;Cc&quot;].split(&quot;,&quot;), msg.as_string())
    smtp.quit()
    


  [1]: http://docs.python.org/library/email.message.html#email.message.Message
  [2]: http://docs.python.org/library/smtplib.html#smtplib.SMTP.sendmail

How to send email to multiple recipients using python smtplib?

How would I do the equivalent of `mv src/* dest/` in Python?

    &gt;&gt;&gt; source_files = &#39;/PATH/TO/FOLDER/*&#39;
    &gt;&gt;&gt; destination_folder = &#39;PATH/TO/FOLDER&#39;
    &gt;&gt;&gt; # equivalent of $ mv source_files destination_folder

[1]: http://docs.python.org/library/os.html

How to move a file in Python?

I have been reading the doc and searching but cannot seem to find a straight answer:

Can you cancel an already executing task? (as in the task has started, takes a while, and half way through it needs to be cancelled)

I found this from the doc at [Celery FAQ][1]

    &gt;&gt;&gt; result = add.apply_async(args=[2, 2], countdown=120)
    &gt;&gt;&gt; result.revoke()

But I am unclear if this will cancel queued tasks or if it will kill a running process on a worker.  Thanks for any light you can shed!



  [1]: http://docs.celeryproject.org/en/latest/faq.html#can-i-cancel-the-execution-of-a-task

Cancel an already executing task with Celery?

suppose we have a model in django defined as follows:

    class Literal:
        name = models.CharField(...)
        ...

Name field is not unique, and thus can have duplicate values. I need to accomplish the following task:
Select all rows from the model that have **at least one duplicate value** of the ``name`` field.

I know how to do it using plain SQL (may be not the best solution):

    select * from literal where name IN (
        select name from literal group by name having count((name)) &gt; 1
    );

So, is it possible to select this using django ORM? Or better SQL solution?



Django select only rows with duplicate field values

I have a very simple query: `select * from tbl1 where title not in(&#39;asdasd&#39;, &#39;asdasd&#39;)`. 

How do I translate that to Django? It&#39;s like I want the opposite of: `Table.objects.filter(title__in=myListOfTitles)`


Django equivalent of SQL not in

I often see people claiming their backend is implemented in Django, but isn&#39;t Django supposed to be for the frontend? I&#39;d assume the backend refers to the business logic where the frontend refers to the presentation. Am I missing something?



Is Django for the frontend or backend?

I need to select several objects to be deleted from my database in django using a webpage. There is no category to select from so I can&#39;t delete from all of them like that. Do I have to implement my own delete form and process it in django or does django have a way to already do this? As its implemented in the admin interface.

Delete multiple objects in django

I&#39;ve tried prefetch_related() in django 1.4 from trunk and can&#39;t make it to prefetch reverse lookup.

My simplified models (each book has many prices):

    class Book(models.Model):
        # some fields
    
    class Price(models.Model):
        book = models.ForeignKey(Book)


My view&#39;s query:
    
    books = Book.objects.prefetch_related(&#39;price&#39;)
    
Then, I got the AttributeError message:
    
    AttributeError: Cannot find &#39;price&#39; on Book object, &#39;price&#39; is an invalid parameter to prefetch_related()


How to make it work?
Thanks.


Django: Does prefetch_related() follow reverse relationship lookup?

Hi I am using the django model class with some field and a password field. Instead of displaying regular plain text I want to display password input. I created a model class like this:

    class UserForm(ModelForm):
        class Meta:
            password = forms.CharField(widget=forms.PasswordInput)
            model = User
            widgets = {
                &#39;password&#39;: forms.PasswordInput(),
            }
But i am getting the following error: NameError: name &#39;forms&#39; is not defined. 

I am using django version 1.4.0. I followed this link : https://stackoverflow.com/questions/3532354/django-password-problems

Still getting the same error. What should i do. Where am i getting wrong.Please help

How to create password input field in django

I would like to change the default behavior of how the admin recent changes sidebar displays the name of &quot;objects&quot; added. Refer to the picture below:


![In the recent actions module, it also shows new objects as &quot;MyModelName object&quot;][2]

  [2]: http://i.stack.imgur.com/bvPjO.png

I would like to change how these are named in the Admin. Ideally, I would like to be able to change it from &quot;MyModelName object&quot; to, as in the &quot;Policy&quot; object example, something like &quot;Policy: {{ value of the policy&#39;s &quot;Policy Name&quot; field. }}. 

I was thinking that `__unicode__` for my Patient model handled this, but it doesn&#39;t appear to. Any assistance is appreciated.

Django &quot;xxxxxx Object&quot; display customization in admin action sidebar

I&#39;m coming from a Rails background, and am having a bit of trouble making use of the &quot;Association Methods&quot; provided in Django.  I have two models (which have been simplified for the sake of brevity), like so:


    class User(models.Model):
        username = models.CharField(max_length=100, unique=True)
        companies = models.ManyToManyField(&#39;Company&#39;, blank=True)

    class Company(models.Model):
        name = models.CharField(max_length=255)

According to the Django documentation:

&gt; &quot;It doesn&#39;t matter which model has the ManyToManyField, but you should only put it in one of the models -- not both.&quot;.

So I understand that if I have an instance of a User, called user, I can do:

    user.companies

My question is how do I do the reverse?  How do I get all users that belong to a Company instance, let&#39;s say Company:

    company.users # This doesn&#39;t work!

What&#39;s the convention to do this?  The documentation that I&#39;ve read doesn&#39;t really cover this.  I need the association to work both ways, so I can&#39;t simply move it from one model to the other.

How to use the &#39;reverse&#39; of a Django ManyToMany relationship?

In Django, I can do this:

    test = Test.objects.get(id=1)
    test.name

I want to be able to access the properties using dynamically generated strings, like this:

    test[&#39;name&#39;]

or, any other syntax using a string.  I tried

    test._meta.get_field_by_name(&#39;name&#39;)

but this returns the field itself and not the value.

Any ideas?

Content Type	Original Author	Original Content on Stackoverflow
Question	Pierre de LESPINAY	View Question on Stackoverflow
Solution 1 - Python	AdamKG	View Answer on Stackoverflow
Solution 2 - Python	Kirill Vladi	View Answer on Stackoverflow

Django - FileField check if None

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

How does the fibonacci recursive function "work"?

TFS: submit changes done locally in one branch to another branch

Attributions