Matt, In C you use a structure with predefined fields names, it would be difficult to use it if names change every time ? In Python, it's technically possible to have variable as keys (interpreted language), you can iterate over keys list of dictionnary to know name of keys and after get the value (dict of properties), but it's not practical , you must fetch name before getting properties every time.
Names must be preset to establish a rigid and well known structure of the output of commands and also to ensure the uniqueness of keys in dictionaries. We try also to respect the semantic of the commands output, in this case, the command "zfs list" return a list of zfs mount point, each mount point is a dictionary of properties (name, used, avail, ..). So the output should be identic : a list of dict --francois 2014-11-17 19:34 GMT+01:00 Matthew Ahrens <[email protected]>: > > > On Mon, Nov 17, 2014 at 10:22 AM, Francois Billard < > [email protected]> wrote: > >> 2014-11-17 18:58 GMT+01:00 Matthew Ahrens <[email protected]>: >> >>> On Mon, Nov 17, 2014 at 9:39 AM, Goulven Riou <[email protected]> >>> wrote: >>> >>>> >>>> Hi Matt, >>>> thanks for your comments on the pull request >>>> we have corrected the style error and applied your suggestions. >>>> >>>> Regarding the dataset name as a key, >>>> the json are consumed by some code and we don't know in advance what >>>> key name >>>> that we will have, so list is preferable to iter over json structure, >>>> >>> >>> Is it not possible / convenient to iterate over the key/value pairs in a >>> JSON structure >>> >> >> Actually it s possible to iterate over key in a json dictionnary, but key >> should stay a key and value a value :) >> > > Yes, and at least in my mind, the dataset name is the key, and the value > is its list of properties. I think you are saying that in the JSON world, > the key should never be a variable? i.e. you always know what the key is > beforehand? > > --matt > > > >> , when your "zfs list -o name" display : >> >> root@t0 # zfs list -o name,used,refer >> NAME USED REFER >> rpool 1.63G 404M >> rpool/ROOT 1.23G 144K >> rpool/ROOT/debian 1.23G 1.23G >> >> the key are NAME, and value are "rpool', and so on >> >> the json output : >> >> "rpool" : { >> "USED" : "1.63G", >> "REFER" : "404M" >> } >> is not good json format (rpool is the value and you have to know the key >> to get the structure which is not convenient -> you have to fetch key name >> in advance) >> >> the good format is (what we have implemented): >> { >> "NAME" : "rpool", >> "USED" : "1.63G", >> "REFER" : "404M" >> } >> >> if you want the structure of a specified pool, you must specify it in the >> command as : >> "zfs list <pool name>" >> >> >> >> >>> could you explain the use case where you need dataset as key name ? >>>> >>> >>>> an other question about the -o option , did you want to block the -o >>>> option with the -J option ? >>>> >>> >>> I thought the whole point was to use -J with -o. Without -o, you will >>> get whatever the default properties are, which could conceivably change >>> over time. >>> >>> >> it's already the case in our implementation. >> >> >>> --matt >>> >>> >>>> best regards >>>> Goulven >>>> >>> >> >> Regards, >> Francois >> > >
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