python - 返回函数不起作用 - new_node 值在内部打印，但在返回时没有返回

Question

def function():
    res = get_nodes(api_server_call, token)
    newnode = ""
    #endTime = ""
    for node in res:
        if (node['state'] == "booting" or node['state'] == "queued"):
            newnode = node['name']
            print("new node is : " + newnode)
            return newnode
    if(newnode == ""):
        function()


new_node = function() >this is main function from where above function is called
print(new_node)

上面的函数返回我正在启动或排队的新节点我正在打印它，但在返回时它返回无

Answer 1

当您不在函数末尾放置 return 语句时，返回 None 是默认行为。如果函数有多种结束方式，则必须以 return 结束每个编码路径，或者在其末尾放置一个。如果你的 newnode 不为空，你什么也不做，所以返回默认值 None。可以肯定的是，在每个代码路径的末尾放置一个有效的 return 语句会更安全：

所以你在函数的最后一行忘记了额外的'return newnode'：

def function():
    res = get_nodes(api_server_call, token)
    newnode = ""
    #endTime = ""
    for node in res:
        if (node['state'] == "booting" or node['state'] == "queued"):
            newnode = node['name']
            print("new node is : " + newnode)
            return newnode

    if(newnode == ""):
        return function()

    return newnode


## main part of the code:
new_node = function() ##>this is main where function is called
print(new_node)