可以使用本函数来生成统一的差异结果文本，只要拿到第一个文本，再通过这个差异文本进行操作，就可以得到第二个文本，从而减少储存两份文件，缩小储存空间。
例子：
#python3.4.3import difflibdiff = difflib.unified_diff(‘one\ntwo\nthree\n’.splitlines(keepends=True),’ore\ntwo\nthree\nemu\n’.splitlines(keepends=True))for line in diff:print(line)
结果输出如下：
—
+++
@@-1,3+1,4@@
-one
+ore
two
three
+emu
通过上面的结果来看，
有了文本比较库的功能，来实现一个文件差异比较工具就是很容易的事情。
例子：
""" Command line interface to difflib.py providing diffs in four formats:* ndiff: lists every line and highlights interline changes.* context: highlights clusters of changes in a before/after format.* unified: highlights clusters of changes in an inline format.* html:generates side by side comparison with change highlights."""import sys, os, time, difflib, optparsedef main():# Configure the option parserusage = "usage: %prog [options] fromfile tofile"parser = optparse.OptionParser(usage)parser.add_option("-c", action="store_true", default=False,help=’Produce a context format diff (default)’)parser.add_option("-u", action="store_true", default=False,help=’Produce a unified format diff’)hlp = ‘Produce HTML side by side diff (can use -c and -l in conjunction)’parser.add_option("-m", action="store_true", default=False, help=hlp)parser.add_option("-n", action="store_true", default=False,help=’Produce a ndiff format diff’)parser.add_option("-l", "–lines", type="int", default=3,help=’Set number of context lines (default 3)’)(options, args) = parser.parse_args()if len(args) == 0:parser.print_help()sys.exit(1)if len(args) != 2:parser.error("need to specify both a fromfile and tofile")n = options.linesfromfile, tofile = args # as specified in the usage string# we’re passing these as arguments to the diff functionfromdate = time.ctime(os.stat(fromfile).st_mtime)todate = time.ctime(os.stat(tofile).st_mtime)with open(fromfile) as fromf, open(tofile) as tof:fromlines, tolines = list(fromf), list(tof)if options.u:diff = difflib.unified_diff(fromlines, tolines, fromfile, tofile,fromdate, todate, n=n)elif options.n:diff = difflib.ndiff(fromlines, tolines)elif options.m:diff = difflib.HtmlDiff().make_file(fromlines, tolines, fromfile,tofile, context=options.c,numlines=n)else:diff = difflib.context_diff(fromlines, tolines, fromfile, tofile,fromdate, todate, n=n)# we’re using writelines because diff is a generatorsys.stdout.writelines(diff)if __name__ == ‘__main__’:main()
在这个例子里，可以使用不同的参数来选择产生比较后文本的结果方式，，比如简单文本方式，也可以
蔡军生 微信号： shenzhencai 深圳
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