adoroszlai commented on pull request #1712:
URL: https://github.com/apache/ozone/pull/1712#issuecomment-746502308
(Answering the part of your comment from #1667 relevant to this PR.)
> The change itself in transformation.py is to go through the items instead
of the collection means that we are transforming something different in those
cases and we do it similarly as the one case you mentioned working well before
this change also, I am not sure though, how this solves the problem.
@fapifta Here's a Python REPL session to show what's going on:
```python
>>> props = {"key": "value"}
>>> props
{'key': 'value'}
>>> props.keys()
['key']
>>> props.values()
['value']
>>> props.items()
[('key', 'value')]
>>> for x in props: print x
...
key
>>> for x in props.keys(): print x
...
key
>>> for x, y in props: print "{}={}".format(x, y)
...
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: too many values to unpack
>>> for x, y in props.items(): print "{}={}".format(x, y)
...
key=value
>>>
```
`props` is a map (dictionary). `for x in props` iterates keys, same as `for
x in props.keys()`. `for x, y in props` also iterates keys (`in props`), but
tries to extract key-value pairs, which fails with `ValueError`, since each key
is only a single item. `for x, y in props.items()` correctly iterates
key-value pairs.
Already used correctly in `to_properties`:
https://github.com/apache/ozone/blob/cbe8651217930181057f7a4e496ae20d891ad032/hadoop-ozone/dist/src/main/dockerlibexec/transformation.py#L81-L85
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