Generate uuid columns

[kerruba-milkman]

Hello,

I'm a newbie of visidata - and in general not a very expert Python developer - but I'm trying to define a command in visidata to generate
a uuid column.

I was able to generate uuids using this function in my .visidatarc

import uuid


#TODO Need to generate value only once and not every time the sheet is updated
def uuidColumn(sourceCol):
    return Column(sourceCol.name+"_uuid", type=str, getter=lambda _, r: uuid.uuid4() )

Sheet.addCommand(None, 'add-uuid-column', 'addColumn(uuidColumn(cursorCol), cursorColIndex+1)', 'generate a uuid v4 column')

the problem is though that I don't want the cell to be recalculated everytime I move my cursor on the sheet. I've also tested the cache=True option, and even if it seems to be quite a good candidate to solve the uuid re-generation, there are actions that trigger the generation anyway.
Instead what I want to achieve is generate the uuid once and that should remain, no re-calculation done

Any help would be fantastic :-)

[saulpw]

Hey @kerruba-milkman, that's an interesting question. One thing you could do is "freeze" (with ') the column after creating it, and then hide the original column and use the new frozen column for everything. You could also incorporate this into your command by using addColumnAtCursor(StaticColumn(uuidColumn(cursorCol))) as the execstr.

Alternatively, you could follow the setcol- command pattern rather than the addcol- pattern, since you want them to be set once and never recalculated. For instance:

@Column.api
@asyncthread
def setcol_uuid(col, rows):
    col.setValues(rows, *[uuid.uuid4() for r in rows])

Sheet.addCommand('', 'setcol-uuid', 'cursorCol.setcol_uuid(someSelectedRows)')

(The @asyncthread is needed in case the number of selected rows is large.)

Now you can create a blank column with za and use setcol-uuid.

[kerruba-milkman]

Hey @saulpw, thanks a lot for your answer, it was definitely useful, and I was able to perform the task with your suggestions.
I still have a couple of questions/notes:

1. The first snippet isn't really working, as I'm getting all the rows in the new column reporting an error 'NoneType' has no attribute 'defer'. Any suggestion on this?
2. The second snippet worked fine, only had to change the method parameter from col to self.

Thanks again for all the help provided.

BTW, the search box on the API docs isn't really working the way I was expecting, or isn't working at all. I was searching for a reference to the cursorCol, and it couldn't find any reference.

[lkhrs]

Hi @kerruba-milkman, a fix is live now for the search issue on the API docs. How does it look on your end? https://www.visidata.org/docs/api/search.html?q=cursorcol

[kerruba-milkman]

Hi @lkhrs, now seems to work fine thanks

[kerruba-milkman]

1. The first snippet isn't really working, as I'm getting all the rows in the new column reporting an error 'NoneType' has no attribute 'defer'. Any suggestion on this?

Actually I found what was the issue.
Basically, I have to pass the sheet object to the Column kwargs in order to be able to refer it later in the self.sheet.defer which was giving me the error.

The final command is therefore this

import uuid

def uuidColumn(sourceCol):
    return Column(sourceCol.name+"_uuid", type=str, getter=lambda c, r: uuid.uuid4(), sheet=sourceCol.sheet)

Sheet.addCommand(None, 'add-uuid-column', 'sheet.addColumnAtCursor(StaticColumn(uuidColumn(cursorCol)))', 'generate a uuid v4 column')

[saulpw]

Nice catch, @kerruba-milkman! yeah, addColumn sets that, which is why it's necessary to call it instead of appending to columns directly. And apparently you can only freeze columns that have their sheet set, which makes sense. Thanks for digging into it!