See the Django 1.11 documentation on ChoiceField. The ’empty value’ for the ChoiceField is defined as the empty string '', so your list of tuples should contain a key of '' mapped to whatever value you want to show for the empty value.
### forms.py
from django.forms import Form, ChoiceField
CHOICE_LIST = [
('', '----'), # replace the value '----' with whatever you want, it won't matter
(1, 'Rock'),
(2, 'Hard Place')
]
class SomeForm (Form):
some_choice = ChoiceField(choices=CHOICE_LIST, required=False)
Note, you can avoid a form error if you want the form field to be optional by using required=False
Also, if you already have a CHOICE_LIST without an empty value, you can insert one so it shows up first in the form drop-down menu:
CHOICE_LIST.insert(0, ('', '----'))