title: Replacing the value of one form field with another
body: <p>I have written a piece of code where the user can select an occupation from a select box (teacher, doctor, pilot, etc) and if their occupation isn't in the list they can select 'other' then write their occupation in a textbox underneath.</p>
  
  <p>I can successfully detect if they selected 'other' from the dropdown box, but cannot figure out how to populate the 'occupation' field with the data from the 'other' field.</p>
  
  <pre><code>if request.method == 'POST':
          form = OccupationForm(request.POST, request.FILES, instance=request.user.occupation)
          if form.is_valid():
              # if user selected 'other' - get input from text field
              if form['occupation'].value() == 'other':
                  # this doesnt work
                  #form_data = self.get_form_step_data(form)
                  #form.other = form_data.get('other', '')
                  #form.save()
                  return redirect('#')
  
              #form.save()
              #return redirect('#')
  
      else:
          form = OccupationForm(instance=request.user.occupation)
  </code></pre>
  
  <p>Thank you.</p>
  
  <p>EDIT:
  shortened models.py</p>
  
  <pre><code>class Occupation(models.Model):
      # I just realized, maybe this should be OneToManyField ??
      user = models.OneToOneField(User, on_delete=models.CASCADE)
  
      OCCUPATIONS = (
          ('teacher', 'Teacher'),
          ('doctor', 'Doctor'),
          ('other', 'Other'),
      )
  
      occupation = models.CharField('What is your job?', max_length=200, null=True, choices=OCCUPATIONS)
  </code></pre>
  
  <p>shortened forms.py</p>
  
  <pre><code>class OccupationsForm(forms.ModelForm):
      other = forms.CharField(required=False, label='')
  
      def clean(self):
          cleaned_data = super().clean()
          if cleaned_data.get('occupations') == 'other':
              cleaned_data['occupations'] = cleaned_data.get('other')
          return cleaned_data
  
      class Meta:
          model = Occupations
  
          fields = ['occupations']
  </code></pre>
  
  <p>Thank you</p>