+from optparse import make_option
+
+def query_yes_no(question, default="yes"):
+ """Ask a yes/no question via raw_input() and return their answer.
+
+ "question" is a string that is presented to the user.
+ "default" is the presumed answer if the user just hits <Enter>.
+ It must be "yes" (the default), "no" or None (meaning
+ an answer is required of the user).
+
+ The "answer" return value is one of "yes" or "no".
+ """
+ valid = {"yes":True, "y":True, "ye":True,
+ "no":False, "n":False}
+ if default == None:
+ prompt = " [y/n] "
+ elif default == "yes":
+ prompt = " [Y/n] "
+ elif default == "no":
+ prompt = " [y/N] "
+ else:
+ raise ValueError("invalid default answer: '%s'" % default)
+
+ while True:
+ sys.stdout.write(question + prompt)
+ choice = raw_input().lower()
+ if default is not None and choice == '':
+ return valid[default]
+ elif choice in valid:
+ return valid[choice]
+ else:
+ sys.stdout.write("Please respond with 'yes' or 'no' "\
+ "(or 'y' or 'n').\n")
+