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

Validating with the extension of a file name is not a consistent way. For example I can rename a picture.jpg into a picture.pdf and the validation won't raise an error.

A better approach is to check the content_type of a file.

Validation Method

def validate_file_extension(value):
    if value.file.content_type != 'application/pdf':
        raise ValidationError(u'Error message')

Usage

actual_file = models.FileField(upload_to='uploaded_files', validators=[validate_file_extension])