How to limit file types on file uploads for ModelForms with FileFields?

Question

My goal is to limit a FileField on a Django ModelForm to PDFs and Word Documents. The answers I have googled all deal with creating a separate file handler, but I am not sur

Answer 1

I use something along these lines (note, "pip install filemagic" is required for this...):

import magic
def validate_mime_type(value):
    supported_types=['application/pdf',]
    with magic.Magic(flags=magic.MAGIC_MIME_TYPE) as m:
        mime_type=m.id_buffer(value.file.read(1024))
        value.file.seek(0)
    if mime_type not in supported_types:
        raise ValidationError(u'Unsupported file type.')

You could probably also incorporate the previous examples into this - for example also check the extension/uploaded type (which might be faster as a primary check than magic.) This still isn't foolproof - but it's better, since it relies more on data in the file, rather than browser provided headers.

Note: This is a validator function that you'd want to add to the list of validators for the FileField model.