How does the fill command work?

[mhoban]

Howdy all-

I'm struggling to understand how to use the fill ('f') command. I got it to work briefly but for some reason I'm doing the same thing again and it's not working. I want to fill empty cells with the value of the first non-empty cell above them. So that something like this:

a	b
A	B
	B
	B
C	E
C	F
	F
	F
D

turns into this:

a	b
A	B
A	B
A	B
C	E
C	F
C	F
C	F
D	F

When I briefly got it to work, I'd select the empty rows and activate the column I was interested in and hit 'f'. I'd have to do this for each block of empty rows. I don't know what changed, but now when I'm trying this it just says "filled 0 values" every time.

At the very least I'd like to understand how to get back to it working the way it (briefly) was before, but ideally there'd be a way to just fill every empty cell with the value of the first non-empty cell above them? That seems to be what's described in the man page.

Obviously the first thing is doable (though I don't know why I can't anymore). Is there a way to do the second thing?

I'm using v3.3, which appears to be the most recent version available on conda-forge.

[midichef]

Fill is skipping your blank cells because it's looking for cells containing Visidata's null value. The null value is almost always Python's None, which is drawn on screen as ⌀. Your cells are blank, which means they contain the empty string ''.

The way I would do it is, change those cells to contain None first: navigate to one of your blank cells. Press , to select all the cells with the same value, then set them to None via gzd (delete-cells). Then press f.

Alternatively, you could change what Visidata considers to be the null value, to the empty string instead of None:
On startup: vd --null-value=''
Or by adding to your .visidatarc: options.null_value = ''
Or, to modify it just for one specific sheet: zO (options-sheet) and edit the value of null_value with e then hit Enter, leaving it blank. (To assign a non-string value like None, you would use z= (setcell-expr).)

As for why it worked for you before, I don't know. Maybe your data was in a fixed-width file, loaded via -f fixed? Fixed-width sheets use a null_value of ''. (The only two sheet types that use a different value of null_value than None are fixed-width sheets and PingSheet.)

[mhoban]

This is very helpful, thank you!