python，生成器迭代一个或多个项目

Question

I'm using pyyaml, and i'm loading a file.yml

stream = open("file.yml", "r")
results = yaml.load_all(stream)

results now contains a generator object.

Then, i'm trying to process this:

for key, value in results:
    print(key, "->", value)

if i have more than one "yaml element" in my file.yml, this works fine. example:

foo: bar

hello: world

but, if i have a only one "yaml element" in my file.yml, this is not working. example:

foo: bar

the error is: ValueError: need more than 1 value to unpack

i'm using python 3

how can i solve this? the file.yml can contains 1 or more elements.

Answer 1

results is a list of dictionaries, so instead of iterating over that, you want to be iterating over the dictionaries:

for dictionary in results:
    for key, value in dictionary.items():
        print(key, "->", value)

So you were trying to assign key to one dictionary, and value to another, because you were unpacking from the list and not the dictionary. dict.items() returns a list of tuples with the key in the first position and the value in the other of the tuple.

Answer 2

results = yaml.load_all(stream)
for doc in results:
    for k, v in doc.items():
        print(k, "->", v)