差别

这里会显示出您选择的修订版和当前版本之间的差别。

--- python-basic:difflib [2010/06/02 01:18]
+++ python-basic:difflib [2010/06/02 01:18] (当前版本)
@@ 行 1: / 行 1: @@
+====== Python difflib|SequenceMatcher|Differ|HtmlDiff 使用方法 ======
+===== 介绍 =====
+difflib 是python提供的比较序列(string list)差异的模块。 \\
+实现了三个类： \\
+   * SequenceMatcher  任意类型序列的比较 (可以比较字符串)
+   * Differ           对字符串进行比较
+   * HtmlDiff         将比较结果输出为html格式
+===== SequenceMatcher 实例 =====
+==== 代码： ====
+<code python>
+import difflib
+from pprint import pprint
+a = 'pythonclub.org is wonderful'
+b = 'Pythonclub.org also wonderful'
+#构造SequenceMatcher类
+s = difflib.SequenceMatcher(None, a, b)
+#得到相同的block
+print "s.get_matching_blocks():"
+pprint(s.get_matching_blocks())
+print
+print "s.get_opcodes():"
+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]))
+    #在此实现你的功能
+</code>
+==== 输出为: ====
+<file>
+s.get_matching_blocks():
+[(1, 1, 14), (16, 17, 1), (17, 19, 10), (27, 29, 0)]
+s.get_opcodes():
+replace a[0:1] (p) b[0:1] (P)
+  equal a[1:15] (ythonclub.org ) b[1:15] (ythonclub.org )
+replace a[15:16] (i) b[15:17] (al)
+  equal a[16:17] (s) b[17:18] (s)
+ insert a[17:17] () b[18:19] (o)
+  equal a[17:27] ( wonderful) b[19:29] ( wonderful)
+</file>
+===== SequenceMatcher find_longest_match BUG=====
+<code python>
+import difflib
+str1 = "Poor Impulse Control: A Good Babysitter Is Hard To Find"
+str2 = """     A Good Babysitter Is Hard To Find    This is Frederick
+by Leo Lionni, the first book I picked for myself.
+I was in kindergarten, I believe, which would be either 1968 or 1969.
+Frederick has a specific lesson for children about how art is as
+important in life as bread, but there's a secondary consideration
+I took away: if we pool our talents our lives are immeasurably better.
+Curiously, this book is the story of my life, however one interprets
+those things. I expect Mickey Rooney to show up any time with a barn
+and a plan for a show, though my mom is not making costumes. My sisters
+own a toy store with a fantastic selection of imaginative children's books.
+I try not to open them because I can't close them and put them back.
+My tantrums are setting a bad example for the kids. Anyway, I mention
+this because yesterday was Mr. Rogers' 40th anniversary. I appreciate
+the peaceful gentleman more as time passes, as I play with finger puppets
+in department meetings, as I eye hollow trees for Lady Elaine Fairchild
+infestations. Maybe Pete can build me trolley tracks!Labels: To Take
+Your Heart Away   """
+s = difflib.SequenceMatcher(None, str1, str2)
+print len(str1), len(str2)
+star_a, start_b, length = s.find_longest_match(0, len(str1)-1, 0, len(str2)-1)
+print star_a, start_b, length
+print str1[star_a:star_a + length]
+</code>
+输出结果为:
+<file>
+1116
+1048 1
+P
+版本为:
+Python 2.5.1 (r251:54863, Apr 18 2007, 08:51:08) [MSC v.1310 32 bit (Intel)] on
+win32
+Type "help", "copyright", "credits" or "license" for more information.
+>>>
+</file>
+而最长的应该为 A Good Babysitter Is Hard To Find.
+==== 解决方法 ====
+将 str1 于 str2 交换一下， len(str1) > len(str2). \\
+则输出结果是想得到的结果。 \\
+**感谢 davies(at)newsmth** \\
+原来这是个已知的bug: http://psf.upfronthosting.co.za/roundup/tracker/issue1528074 \\
+第二个字符串长度不能超过200，\\
+Work Around为: 将较长的字符串设为第一个，而较短的设为第二个。

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