from xml.dom.minidom import parse, parseString

attr_val = "multiline\nvalue"
attr_name = 'attr'
document = '<foo ' + attr_name + '="' + attr_val + '" />'

dom_1 = parseString(document)
attr1 = dom_1.firstChild.getAttribute(attr_name)

dom_2 = parseString('<xml />')
dom_2.firstChild.setAttribute(attr_name, attr_val)
attr2 = dom_2.firstChild.getAttribute(attr_name)

print attr1 == attr2