def lookups(k, key): """Yield one lookup function for each node of k that has the label key. >>> k = tree(5, [tree(7, [tree(2)]), tree(8, [tree(3), tree(4)]), tree(5, [tree(4), tree(2)])]) >>> v = tree('Go', [tree('C', [tree('C')]), tree('A',

代码不完整，但是根据函数名和示例代码，我们可以猜测该函数的作用是在一棵树中查找标签为 key 的节点，并且返回一个生成器，每次生成一个函数，该函数可以查找一个满足要求的节点。

下面是完整的代码实现：

def lookups(k, key):
    if label(k) == key:
        yield lambda: k
    for b in branches(k):
        yield from lookups(b, key)
        # 等价于 yield from list(lookups(b, key))

首先，我们判断当前节点的标签是否为 key，如果是，则生成一个 lambda 函数，该函数返回当前节点 k。

如果当前节点不是要查找的节点，那么我们需要遍历当前节点的每个子节点，对于每个子节点，我们再次调用 lookups 函数，查找标签为 key 的节点。这里使用了 yield from 语句，将子节点的查找结果直接作为生成器的输出，避免了递归过程中生成器嵌套的问题。

最终，我们得到一个生成器，每次生成一个函数，该函数可以查找一个满足要求的节点。

相关问题

## Problem 4: Trictionary or Treat  A trictionary is a pair of tree `k` and `v`. They have identical structure: each node in `k` has a corresponding node in `v`. The labels in `k` are called keys. Each key may be the label for multiple nodes in `k`, and the values for that key are the labels of all the corresponding nodes in `v`. A lookup function returns one of the values for a key. Specifically, a lookup function for a node in `k` is a function that takes `v` as an argument and returns the label for the corresponding node in `v`. Implement the generator function `lookups`, which takes as input a tree `k` and a key. It yields all lookup functions for nodes in `k` that have key as their label, the functions could be yielded in any order. ```python def lookups(k, key): """Yield one lookup function for each node of k that has the label key. >>> k = tree(5, [tree(7, [tree(2)]), tree(8, [tree(3), tree(4)]), tree(5, [tree(4), tree(2)])]) >>> v = tree('Go', [tree('C', [tree('C')]), tree('A', [tree('S'), tree(6)]), tree('L', [tree(1), tree('A')])]) >>> type(lookups(k, 4)) <class 'generator'> >>> sorted([f(v) for f in lookups(k, 2)]) ['A', 'C'] >>> sorted([f(v) for f in lookups(k, 3)]) ['S'] >>> [f(v) for f in lookups(k, 6)] [] """ "*** YOUR CODE HERE ***" ```

这道题需要实现一个 `lookups` 生成器函数，它的输入参数是两棵树 `k` 和一个 key，输出结果是所有在 `k` 中标签为 key 的节点对应的在 `v` 中的节点的标签。

我们可以使用递归的方式遍历树 `k`，对于每个节点，如果它的标签等于 key，则生成一个 lookup 函数，该函数的输入为 `v`，输出为对应节点在 `v` 中的标签；否则递归遍历它的子节点。最终，我们需要将所有生成的 lookup 函数作为生成器的输出。

以下是实现代码：

def lookups(k, key):
    """
    Yield one lookup function for each node of k that has the label key.
    """
    if label(k) == key:
        yield lambda v: label(v)
    for child_k, child_v in zip(children(k), children(v)):
        yield from lookups(child_k, child_v)

其中的 `label` 函数返回节点的标签，`children` 函数返回节点的子节点列表。`yield from` 可以将子生成器产生的值逐一地传递给父生成器的调用者。

这段代码首先判断当前节点的标签是否等于 key，如果是，则生成一个新的 lookup 函数，否则递归遍历子节点，并将生成的 lookup 函数加入生成器中。

注意，这里的 `v` 是在函数定义时未定义的，它应该在调用 `lookups` 函数时作为参数传入。

A trictionary is a pair of tree k and v. They have identical structure: each node in k has a corresponding node in v. The labels in k are called keys. Each key may be the label for multiple nodes in k, and the values for that key are the labels of all the corresponding nodes in v. A lookup function returns one of the values for a key. Specifically, a lookup function for a node in k is a function that takes v as an argument and returns the label for the corresponding node in v. Implement the generator function lookups, which takes as input a tree k and a key. It yields all lookup functions for nodes in k that have key as their label, the functions could be yielded in any order.

Sure, here's a Python implementation of the `lookups` generator function:

def lookups(k, key):
    """
    Generate all lookup functions for nodes in tree k with label key.
    """
    def lookup_fn(node):
        """
        Return the label of the corresponding node in v for a given node in k.
        """
        return node.value

    for node in k.traverse():
        if node.label == key:
            yield lookup_fn

Explanation:

- The `lookups` function takes two arguments: `k`, the tree, and `key`, the label we want to look up.
- The inner function `lookup_fn` takes a node in `v` as an argument and returns its label.
- The function `lookups` uses a `for` loop to traverse all nodes in `k`.
- For each node, it checks whether its label is equal to `key`.
- If the label matches, it yields the `lookup_fn` function for that node.

Note that the implementation assumes that the `Tree` class has a `traverse` method that returns all nodes in the tree in some order, and that each node has a `label` and a `value` attribute. You may need to modify the implementation to match the specifics of your `Tree` class.