Filter with Variable

Dear All,

Just another small question.
Is there a way to use a variable to do an exclude/filter ?
For example, something like this (the real name pf the filed is email :

my_field = 'email'
my_people = Objects.objects.all().exclude(my_field ="§").exclude(my_field="").exclude(my_field=None)

But I got the error :
FieldError: Cannot resolve keyword ‘my_field’ into field

See the threads at Dynamic queryset and Reusable Queries with Q.