Initially populate FileField in Django-Form
<p>I have a model that describes a Webpage. The <code>source_upload</code> field represents a screenshot of the webpage. </p>

<p>For adding site-objects to my application, I use a django class-based <code>CreateView</code>. This works really well. </p>

<p>Now I'm trying to add a semi-automatic way of adding sites. You can pass an URL to the view and the view fills the form automatically (and makes a screenshot of the webpage). The user should be able to review all the auto-extracted fields - especially the auto generated screenshot image - change them and hit the save button to add the object to the database and the image (if approved) to its final location.</p>

<p>I tried to implement this in the <code>get_initial</code> method of the view. This works quite well except for the screenshot-<code>FileField</code>. The path I set in <code>initial['source_upload']</code> is not shown in the <code>current: &lt;link&gt;</code>part of the FileInput widget of the form.</p>

<p><strong>How can I give the filefield an initial value?</strong></p>

<hr>

<p><strong>models.py</strong></p>

<pre><code>class Site(models.Model):

    def get_source_upload_path(instance, filename):
        now = datetime.datetime.now()
        return "appname/sites/{}/{}/{}/site_{}_{}".format(now.year, now.month, now.day, instance.pk, filename)

    creationDate = models.DateTimeField(auto_now_add=True)
    last_modifiedDate = models.DateTimeField(auto_now=True)
    creator = models.ForeignKey('auth.User', related_name='siteCreated')
    last_modifier = models.ForeignKey('auth.User', related_name='siteLast_modified')

    date = models.DateTimeField(default=datetime.date.today)    
    title = models.CharField(max_length=240, blank=True)
    body = models.TextField(max_length=3000)

    source_url = models.URLField(blank=True)
    source_upload = models.FileField(upload_to=get_source_upload_path, blank=True)

    keywords = models.ManyToManyField("Keyword")
</code></pre>

<p><strong>urls.py</strong></p>

<pre><code>url(r'site/add/$', views.SiteCreate.as_view(), name='site-add'),
url(r'site/add/(?P&lt;source_url&gt;[A-Za-z0-9\-._~:/\[\]@!$&amp;\'\(\)\*\+,;=?#]+)/$', views.SiteCreate.as_view(), name='site-add-fromurl'),
</code></pre>

<p><strong>forms.py</strong></p>

<pre><code>class SiteForm(ModelForm):
    class Meta:
        model = Site
        fields = ['date', 'title', 'body', 'source_url', 'source_upload', 'keywords']
        widgets = {
            'keywords' : CheckboxSelectMultiple(),
        }
</code></pre>

<p><strong>views.py</strong></p>

<pre><code>class SiteCreate(LoginRequiredMixin, CreateView):
    model = Site
    template_name = 'appname/site_form.html'
    form_class = SiteForm
    success_url = reverse_lazy('appname:index')

    def form_valid(self, form):
        form.instance.creator = self.request.user
        form.instance.last_modifier = self.request.user
        return super(SiteCreate, self).form_valid(form)

    def get_initial(self):
        # Get the initial dictionary from the superclass method
        initial = super(SiteCreate, self).get_initial()

        try:
            #get target url from request
            fullpath = self.request.get_full_path()
            fullpath = fullpath.split("/")
            fullpath, querystring = fullpath[3:-1], fullpath[-1]
            source_domain = fullpath[2]
            fullpath = "/".join(fullpath)
            fullpath += querystring

            source_url = fullpath

            if (not source_url.startswith("http://") and not source_url.startswith("https://")):
                print("ERROR: url does not start with http:// or https://")
                return initial

            # ...
            # extract title, date &amp; others with BeautifulSoup
            # ...

            #extract screenshot  (is there a better way?)
            from selenium import webdriver
            driver = webdriver.Firefox()
            driver.get(source_url)
            tmpfilename = "{}_{}.png".format(get_valid_filename(source_domain), get_valid_filename(title[:30]))
            now = datetime.datetime.now()
            tmpfilepath_rel =  "appname/sites/tmp/{}/{}/{}/{}".format(now.year, now.month, now.day, tmpfilename)
            tmpfilepath = settings.MEDIA_ROOT + tmpfilepath_rel

            folder=os.path.dirname(tmpfilepath)
            if not os.path.exists(folder):
                os.makedirs(folder)
            driver.save_screenshot(tmpfilepath)
            driver.quit()

            initial = initial.copy()
            initial['source_url'] = source_url
            initial['title'] = title
            initial['date'] = soup_date
            initial['body'] = body
            initial['source_upload'] = tmpfilepath_rel
        except KeyError as e:
            print("no valid source_url found. zeige also ganz normales add/new template")
        except IndexError as e:
            print("no valid source_url found. zeige also ganz normales add/new template")

        return initial
</code></pre>

<p><strong>site_form.html</strong> (Used for Create and Update view)</p>

<pre><code>{% extends "appname/base.html" %}
{% load staticfiles %}
{% block header %}
    &lt;link rel="stylesheet" type="text/css" href="{% static 'appname/model_forms.css' %}" /&gt;
{% endblock %}
{% block body %}
        &lt;form enctype="multipart/form-data" action="" method="post"&gt;{% csrf_token %}

            &lt;div class="fieldWrapper"&gt;
                &lt;div class="error"&gt;{{ form.date.errors }}&lt;/div&gt;
                &lt;div class="label"&gt;{{ form.date.label_tag }}&lt;/div&gt;
                &lt;div class="field"&gt;{{ form.date }}&lt;br /&gt;{{ form.date.help_text }}&lt;/div&gt;
                &lt;div class="floatclear"&gt;&lt;/div&gt;
            &lt;/div&gt;
            &lt;div class="fieldWrapper"&gt;
                &lt;div class="error"&gt;{{ form.title.errors }}&lt;/div&gt;
                &lt;div class="label"&gt;{{ form.title.label_tag }}&lt;/div&gt;
                &lt;div class="field"&gt;{{ form.title }}&lt;br /&gt;{{ form.title.help_text }}&lt;/div&gt;
                &lt;div class="floatclear"&gt;&lt;/div&gt;
            &lt;/div&gt;
            &lt;div class="fieldWrapper"&gt;
                &lt;div class="error"&gt;{{ form.body.errors }}&lt;/div&gt;
                &lt;div class="label"&gt;{{ form.body.label_tag }}&lt;/div&gt;
                &lt;div class="field"&gt;{{ form.body }}&lt;br /&gt;{{ form.body.help_text }}&lt;/div&gt;
                &lt;div class="floatclear"&gt;&lt;/div&gt;
            &lt;/div&gt;
            &lt;div class="fieldWrapper"&gt;
                &lt;div class="error"&gt;{{ form.source_url.errors }}&lt;/div&gt;
                &lt;div class="label"&gt;{{ form.source_url.label_tag }}&lt;/div&gt;
                &lt;div class="field"&gt;{{ form.source_url }}&lt;br /&gt;{{ form.source_url.help_text }}&lt;/div&gt;
                &lt;div class="floatclear"&gt;&lt;/div&gt;
            &lt;/div&gt;
            &lt;div class="fieldWrapper"&gt;
                &lt;div class="error"&gt;{{ form.source_upload.errors }}&lt;/div&gt;
                &lt;div class="label"&gt;{{ form.source_upload.label_tag }}&lt;/div&gt;
                &lt;div class="field"&gt;{{ form.source_upload }}&lt;br /&gt;{{ form.source_upload.help_text }}&lt;/div&gt;
                &lt;div class="floatclear"&gt;&lt;/div&gt;
            &lt;/div&gt;
            &lt;div class="fieldWrapper"&gt;
                &lt;div class="error"&gt;{{ form.keywords.errors }}&lt;/div&gt;
                &lt;div class="label"&gt;{{ form.keywords.label_tag }}&lt;/div&gt;

                &lt;div class="field"&gt;
                    &lt;ul class="checkbox-grid"&gt;
                        {% for kw in form.keywords %}
                            &lt;li&gt;
                                {{ kw.tag }}
                                &lt;label for="{{ kw.id_for_label }}"&gt;
                                    {{ kw.choice_label }}
                                &lt;/label&gt;
                            &lt;/li&gt;
                        {% endfor %}
                    &lt;/ul&gt;
                    &lt;div class="checkbox_help_text"&gt;&lt;br /&gt;{{ form.keywords.help_text }}&lt;/div&gt;
                &lt;/div&gt;
                &lt;div class="floatclear"&gt;&lt;/div&gt;
            &lt;/div&gt;
            &lt;input type="submit" value="Save" /&gt;
        &lt;/form&gt;
        &lt;div id="ObjectHistory"&gt;
            {% if site.pk %}
                &lt;p&gt;Created by: {{ site.creator }}&lt;/p&gt;
                &lt;p&gt;Created on: {{ site.creationDate }}&lt;/p&gt;
                &lt;p&gt;Last modified by: {{ site.last_modifier }}&lt;/p&gt;
                &lt;p&gt;Last modified on: {{ site.last_modifiedDate }}&lt;/p&gt;
                &lt;p&gt;Now: {% now "Y-m-d H:i:s" %} &lt;a href="{% url 'appname:site-delete' site.pk %}"&gt;&lt;button&gt;delete&lt;/button&gt;&lt;/a&gt;&lt;/p&gt;
            {% else %}
                &lt;p&gt;This is a new Site!&lt;/p&gt;
                &lt;p&gt;Now: {% now "Y-m-d H:i:s" %}&lt;/p&gt;
            {% endif %}
        &lt;/div&gt;
{% endblock %}
</code></pre>