Python in visidata

[Shahin-rmz]

Hello,
the more I use Visidata, the more fall in love with it.
2 questions, maybe newbe ones.
can not find good documentation where shows how to use Python inside Visidata. Could someone please show me any links if there are any?
2. how can I choose not null values inside a column?
thanks for your time

[anjakefala]

These are not newbe questions at all!

For the second one, the answer can be found here: https://www.visidata.org/docs/rows/

How to select rows where the current column is not null or empty?

'Null' cells, by default, are cells which contain None. This can be changed with options.null_value. Null cells can be set with zd (set current cell to None) or gzd (set selected rows in current column to None). Null cells are distinguished with a yellow ∅' symbol on the right hand corner. They are distinct from empty cells (which are '' in columns of string type.)
Type | followed by . to select all rows without empty or null cells in the current column.

[Shahin-rmz]

Thanks @anjakefala for your answer.
with your help and the documentation, I could manage to change the #Err to ∅ symbol. how ever, wanted to know if there is better way to do it than manually select them via | and regex and then do gzd.
But your answer was intuitive.
Thanks

[anjakefala]

For the first, I do not think there is good comprehensive documentation about this, yet.

Essentially, there are commands that accept regex expressions and Python expressions. For the ones that accept Python expressions, you can pass column names as variables, and the expression will be performed on every row in that column.

For example, = (expr-col), you could type (Column_A + 2). This will create a new column. For each row in Column_A, the contents will be +2, and then the solution will be placed in that same row in the new column. A good overview of this command can be found here: https://jsvine.github.io/intro-to-visidata/intermediate/creating-new-columns/#how-to-create-an-expression-column.

Other example commands that accept Python expressions are z| (select by Python expression), z/ (search by Python expression), Ctrl+X and friends (evaluate the Python expression, and open a new PythonObj sheet). It would be good to have documentation for these.

To learn which commands accept a Python expression as input, you can open the manpage (g Ctrl+H within VisiData), then type / python, and scroll through with n/N. =)

[Shahin-rmz]

Thanks @anjakefala for your answers. actually what I meant was opening vim within visidata, and then, define a function like that,

def awesome_visidata(current_col):
    if foo :
        do some advanced functions
    elif bar:
        do some other advanced functions

By Python within visidata, I meant that. not python regex expressions :)

[saulpw]

It's a good idea, @Shahin-rmz! This is not quite possible, though you can use exec-python and then Ctrl+O to launch your $EDITOR. It just doesn't get saved into the globals dict like you'd expect :) Maybe someday.

[saulpw]

Okay, now symbols defined in exec-python are saved into the globals dict, and will be available for use in expressions! So you can do:

1. <space>exec-python<enter> to start the command (there is no keybinding, but you can also find it under System > Python > exec())
2. Ctrl+O to open the input in your $EDITOR (if set).
3. Type out the code you want, save and quit when done.
4. Press <enter> at the input prompt to accept the input.
5. Now you should be able to use the definitions in subsequent expressions!

[Shahin-rmz]

It's simply fabulous.
with your help, I could manage to open my editor (which is of course Vim).

two things to mention though,

• the editor behaves the code as plain text, not python script. should I manually add #!/usr/bin/env python3 to the beginning?

• I want to know how you perform functions on the columns (it is not pandas and I don't know how to call columns and do the functions), if you could link an example it would be awesome.

thanks

[saulpw]

To use a function that you define, use =awesome_visidata(current_col).

For the other question, vim has a filetype setting you can pass as an argument.

[ghost]

@Shahin-rmz Have a look at these discussions where I've been trying to understand similar things. I don't know if you can define a function 'live' inside visidata, but you can certainly define a function in your .visidatarc which will load when you start visidata and be available for you to use inside Python expressions. If you get more serious, you can also create Python plugins:

• Adding Python functions to ~/.visidatarc
• Puzzling out plugin creation