我不明白这很重要

Question

def edits1(word):
  "All edits that are one edit away from `word`."
  letters    = 'abcdefghijklmnopqrstuvwxyz'
  splits     = [(word[:i], word[i:])    for i in range(len(word) + 1)]
  deletes    = [L + R[1:]               for L, R in splits if R]
  transposes = [L + R[1] + R[0] + R[2:] for L, R in splits if len(R)>1]
  replaces   = [L + c + R[1:]           for L, R in splits if R for c in letters]
  inserts    = [L + c + R               for L, R in splits for c in letters]
  return set(deletes + transposes + replaces + inserts)

此方法是从python代码中复制的，该代码用于在输入时预测单词。我想知道为什么在R for c in letters中使用'R'很重要。

Answer 1

变量splits如下所示：

[('', 'word'), ('w', 'ord'), ('wo', 'rd'), ('wor', 'd'), ('word', '')]

后续分配使用L（左）和R（右）来引用此列表中的每对元素。因此，对于第二个元素，L == 'w'和R == 'ord'。

如果我们采用L和R的值，则此行：

transposes = [L + R[1] + R[0] + R[2:] for L, R in splits if len(R)>1] 

给出'w' + 'r' + 'o' + 'd'，换句话说，它交换R的前两个字母，以使'ord'变成'rod'。