docs: add column with predefined values

[rosmur]

Please describe the issue

Lacking basic documentation on how to add a column with a predefined value. Eg: I want to add a new column with the values set at "this".

table.mutate(new_col="this") does not work.

Code of Conduct

• I agree to follow this project's Code of Conduct

[cpcloud]

The way this is done is with ibis.literal:

In [5]: from ibis.interactive import *

In [6]: t = ibis.memtable({"col": [1, 2, 3]})

In [7]: t
Out[7]:
┏━━━━━━━┓
┃ col   ┃
┡━━━━━━━┩
│ int64 │
├───────┤
│     1 │
│     2 │
│     3 │
└───────┘

In [8]: t.mutate(new_col=ibis.literal("this"))
Out[8]:
┏━━━━━━━┳━━━━━━━━━┓
┃ col   ┃ new_col ┃
┡━━━━━━━╇━━━━━━━━━┩
│ int64 │ string  │
├───────┼─────────┤
│     1 │ this    │
│     2 │ this    │
│     3 │ this    │
└───────┴─────────┘

I thought we had some documentation around this in our getting started bits, but perhaps not!

[rosmur]

Thanks, please add to docs!!

I want to use ibis but the documentation has completely ruined the onboarding and I'm finding I just slide back to Polars/pandas most times.

Even the LLMs give incorrect answers, likely as the documentation is lacking.

[romaingd]

/take

[romaingd]

Thanks for the issue @rosmur. A dedicated example was added to the Getting started docs, hopefully it correctly addresses your concern!