A gross simple state machine

join_quoted_strs.py

def join_quoted_strs(s):
	r = ''
	within_quotes = False
	is_escaped = False
	for c in s:
		if within_quotes:
			if is_escaped:
				r += c
				is_escaped = False
			else:
				if c == '\\':
					is_escaped = True
				elif c == '"':
					within_quotes = False
				else:
					r += c
		else:
			if c == '"':
				within_quotes = True
			else:
				assert c == " "
	return r