The django documentation for newforms gives an example of how to extend the forms.Field class here.
A snippet is shown below.
from django import newforms as forms
class MultiEmailField(forms.Field):
def clean(self, value):
emails = value.split(',')
for email in emails:
if not is_valid_email(email):
raise forms.ValidationError('%s is not \
a valid e-mail address.' % email)
if not emails:
raise forms.ValidationError('Enter at least \
one e-mail address.')
return emails
What is wrong with this code?
The variable value is always a string (an empy one “” if value is None).
The python#str split operation returns a list of either the substrings which make up the original or it returns a list with the original string in it if not split.
For instance
“boy girl cat”.split(” “) ==> [’boy’, ‘girl’, ‘cat’]
and
“boy girl cat”.split(”,”) ==> [”boy girl cat”]
Of course in the case where our original string is empty, the returned result is [”"].
Now, in python, you can use None, [], {} as the predicate in your if-else clause.
At this point in the code,
if not emails:
raise forms.Valid.......
The author of the above code intended to do so, but was thwarted as he is instead testing a predicate which will never be false.
The question that then arises is who is to blame?
The user: For failing to realise the behaviour of the python split function?
or
The language authors: Who should perhaps return as truly empty list [] not [”"] when split is called on an empty string?
