Patch #1413711: Certain patterns of differences were making difflib
touch the recursion limit. The applied patch inlines the recursive
__helper method in a non-recursive way.
diff --git a/Lib/difflib.py b/Lib/difflib.py
index 3558f53..55f69ba 100644
--- a/Lib/difflib.py
+++ b/Lib/difflib.py
@@ -473,27 +473,32 @@
if self.matching_blocks is not None:
return self.matching_blocks
- self.matching_blocks = []
la, lb = len(self.a), len(self.b)
- self.__helper(0, la, 0, lb, self.matching_blocks)
+
+ indexed_blocks = []
+ queue = [(0, la, 0, lb)]
+ while queue:
+ # builds list of matching blocks covering a[alo:ahi] and
+ # b[blo:bhi], appending them in increasing order to answer
+ alo, ahi, blo, bhi = queue.pop()
+
+ # a[alo:i] vs b[blo:j] unknown
+ # a[i:i+k] same as b[j:j+k]
+ # a[i+k:ahi] vs b[j+k:bhi] unknown
+ i, j, k = x = self.find_longest_match(alo, ahi, blo, bhi)
+
+ if k:
+ if alo < i and blo < j:
+ queue.append((alo, i, blo, j))
+ indexed_blocks.append((i, x))
+ if i+k < ahi and j+k < bhi:
+ queue.append((i+k, ahi, j+k, bhi))
+ indexed_blocks.sort()
+
+ self.matching_blocks = [elem[1] for elem in indexed_blocks]
self.matching_blocks.append( (la, lb, 0) )
return self.matching_blocks
- # builds list of matching blocks covering a[alo:ahi] and
- # b[blo:bhi], appending them in increasing order to answer
-
- def __helper(self, alo, ahi, blo, bhi, answer):
- i, j, k = x = self.find_longest_match(alo, ahi, blo, bhi)
- # a[alo:i] vs b[blo:j] unknown
- # a[i:i+k] same as b[j:j+k]
- # a[i+k:ahi] vs b[j+k:bhi] unknown
- if k:
- if alo < i and blo < j:
- self.__helper(alo, i, blo, j, answer)
- answer.append(x)
- if i+k < ahi and j+k < bhi:
- self.__helper(i+k, ahi, j+k, bhi, answer)
-
def get_opcodes(self):
"""Return list of 5-tuples describing how to turn a into b.