如何逐行比较两个不同的文件并在第三个文件中写入差异？

如何逐行比较两个不同的文件并在第三个文件中写入差异？

如果您使用的是* nix系统，最好的通用选项只是使用：

sort filea fileb | uniq -u

但是，如果您需要使用Python：

您的代码在外部文件的每次迭代中都会重新打开内部文件。在循环外打开它。

使用嵌套循环比循环遍历第一个存储找到的值，然后将第二个与这些值进行比较的效率低。

def build_set(filename):    # A set stores a collection of unique items.  Both adding items and searching for them    # are quick, so it's perfect for this application.    found = set()    with open(filename) as f:        for line in f: # [:2] gives us the first two elements of the list. # Tuples, unlike lists, cannot be changed, which is a requirement for anything # being stored in a set. found.add(tuple(sorted(line.split()[:2])))    return foundset_more = build_set('100rwsnMore.txt')set_del = build_set('100rwsnDeleted.txt')with open('results.txt', 'w') as out_file:   # Using with to open files ensures that they are properly closed, even if the pre   # raises an exception.   for res in (set_more - set_del):      # The - computes the elements in set_more not in set_del.      out_file.write(" ".join(res) + "n")