%s を定義済み/空でない変数文字列に置き換えるにはどうすればよいですか? むしろ、そうするためのPythonicまたは構文糖は何ですか?
例:
# Replace %s with the value if defined by either vehicle.get('car') or vehicle.get('truck')
# Assumes only one of these values can be empty at any given time
# The get function operates like http://docs.python.org/2/library/xml.etree.elementtree.html#xml.etree.ElementTree.Element.get
logging.error("Found duplicate entry with %s", vehicle.get('car') or vehicle.get('truck'))