生成器Python的返回列表

Question

I'm trying to make a customize version for DFS from the original version of networkx. You can relate to the original version of DFS from networkx here: networkx DFS

In my implementation, I want to add a child which contain "if" in the label to a list and return the list after all but I can't make it

def extract_expression(label):
    m = re.search('if(.+?)goto', label)
    if m:
       return m.group(1)
    return None

def dfs_edges(G, source=None):  
    path = list()
    if source is None:
        nodes = G
    else:
        nodes = [source]
    visited=set()
    for start in nodes:
        if start in visited:
            continue
        visited.add(start)
        stack = [(start,iter(G[start]))]
        while stack:
            parent,children = stack[-1]
            try:
                child = next(children)
                label = G.node[child]['label']
                if "if" in label:
                    print child
                    # print extract_expression(label)
                exp = extract_expression(label)
                path.append(exp)
                if child not in visited:
                    yield parent,child      
                    visited.add(child)
                    stack.append((child,iter(G[child])))
            except StopIteration:
                stack.pop()
    return path

Throw the error

    return path
SyntaxError: 'return' with argument inside generator

Answer 1

A generator function must always yield its result.

You could simply replace the return path with yield path but that would be bad practice and overall inconsistent. You'd return the parent, child and at one time suddenly get a list.