import itertools import re import diff_match_patch def side_by_side_diff(old_text, new_text): """ Calculates a side-by-side line-based difference view. Wraps insertions in and deletions in . """ def yield_open_entry(open_entry): """ Yield all open changes. """ ls, rs = open_entry # Get unchanged parts onto the right line if ls == rs: yield (False, ls, rs) for l, r in itertools.izip_longest(ls[1:], rs[1:]): yield (True, l, r) elif ls[-1] == rs[-1]: for l, r in itertools.izip_longest(ls[:-1], rs[:-1]): yield (l != r, l, r) yield (False, ls[-1], rs[-1]) else: for l, r in itertools.izip_longest(ls, rs): yield (True, l, r) line_split = re.compile(r'(?:\r?\n)') dmp = diff_match_patch.diff_match_patch() diff = dmp.diff_main(old_text, new_text) dmp.diff_cleanupSemantic(diff) open_entry = ([None], [None]) for change_type, entry in diff: assert change_type in [-1, 0, 1] entry = (entry.replace('&', '&') .replace('<', '<') .replace('>', '>')) lines = line_split.split(entry) # Merge with previous entry if still open ls, rs = open_entry line = lines if line: if change_type == 0: ls[-1] = ls[-1] or '' rs[-1] = rs[-1] or '' ls[-1] = ls[-1] + line rs[-1] = rs[-1] + line elif change_type == 1: rs[-1] = rs[-1] or '' rs[-1] += '%s' % line if line else '' elif change_type == -1: ls[-1] = ls[-1] or '' ls[-1] += '%s' % line if line else '' lines = lines[1:] if lines: if change_type == 0: # Push out open entry for entry in yield_open_entry(open_entry): yield entry # Directly push out lines until last for line in lines[:-1]: yield (False, line, line) # Keep last line open open_entry = ([lines[-1]], [lines[-1]]) elif change_type == 1: ls, rs = open_entry for line in lines: rs.append('%s' % line if line else '') open_entry = (ls, rs) elif change_type == -1: ls, rs = open_entry for line in lines: ls.append('%s' % line if line else '') open_entry = (ls, rs) # Push out open entry for entry in yield_open_entry(open_entry): yield entry