python diff SequenceMatcher - 修补列表

Question

我修补了一个列表，使其看起来像另一个列表:

a = [x for x in "qabxcd"]
b = [x for x in "abycdf"]
c = a[:]
s = SequenceMatcher(None, a, b)
for tag, i1, i2, j1, j2 in s.get_opcodes():
    print ("%7s a[%d:%d] (%s) b[%d:%d] (%s)" % 
    (tag, i1, i2, a[i1:i2], j1, j2, b[j1:j2]))
    if tag == "delete":
        del c[i1:i2]
    elif tag == "replace":
        c[i1:i2] = b[j1-1:j2-1]
    elif tag == "insert":
        c[i1:i2] = b[j1:j2]
print c
print b
print c == b
a == b

但列表不相等:

 delete a[0:1] (['q']) b[0:0] ([])
  equal a[1:3] (['a', 'b']) b[0:2] (['a', 'b'])
replace a[3:4] (['x']) b[2:3] (['y'])
  equal a[4:6] (['c', 'd']) b[3:5] (['c', 'd'])
 insert a[6:6] ([]) b[5:6] (['f'])
['a', 'b', 'x', 'b', 'd', 'f']
['a', 'b', 'y', 'c', 'd', 'f']
False

问题是什么？

Answer 1

所有 Action 都会移动索引。当我愿意这样做时，我必须计算变化:

a = [x for x in "abyffgh fg99"]
b = [x for x in "999aby99ff9h9"]
c = a[:]

s = SequenceMatcher(None, a, b)

i = 0
for tag, i1, i2, j1, j2 in s.get_opcodes():
    print ("%7s a[%d:%d] (%s) b[%d:%d] (%s) c[%d:%d] (%s)" % 
    (tag, i1, i2, a[i1:i2], j1, j2, b[j1:j2], i1, i2, c[i1 + i:i2 + i]))
    if tag == "delete":
        del c[i1 + i:i2 + i]
        i -= i2 - i1
    elif tag == "replace":
        c[i1 + i:i2 + i] = b[j1:j2]
        i -= i2 - i1 - j2 + j1
    elif tag == "insert":
        c[i1 + i:i2 + i] = b[j1:j2]
        i += j2 - j1
    print c
    print i
print c
print b
print c == b
a == b

输出:

['9', '9', '9', 'a', 'b', 'y', '9', '9', 'f', 'f', '9', 'h', ' ', 'f', 'g', '9', '9']
5
 delete a[7:10] ([' ', 'f', 'g']) b[12:12] ([]) c[7:10] ([' ', 'f', 'g'])
['9', '9', '9', 'a', 'b', 'y', '9', '9', 'f', 'f', '9', 'h', '9', '9']
1
  equal a[10:11] (['9']) b[12:13] (['9']) c[10:11] (['h'])
['9', '9', '9', 'a', 'b', 'y', '9', '9', 'f', 'f', '9', 'h', '9', '9']
1
 delete a[11:12] (['9']) b[13:13] ([]) c[11:12] (['9'])
['9', '9', '9', 'a', 'b', 'y', '9', '9', 'f', 'f', '9', 'h', '9']
-1
['9', '9', '9', 'a', 'b', 'y', '9', '9', 'f', 'f', '9', 'h', '9']
['9', '9', '9', 'a', 'b', 'y', '9', '9', 'f', 'f', '9', 'h', '9']
True