How to create a json column, based on other columns?

[felipeangelimvieira]

Hello,

Thank you for this amazing lib.
I didn't find on the docs how to create a JSON column from other columns, something like:

tbl = tbl.mutate(
json_column=ibis.json({"column_b": _.ColumnB})
)

Is there a way to achieve this?

[gforsyth]

Hwy @felipeangelimvieira -- if the backend supports JSON and the column you want to convert can be coerced into JSON, then you can accomplish this with a cast:

[ins] In [18]: t
Out[18]: 
┏━━━━━━━┳━━━━━━━━━━━━━━━━━━┓
┃ a     ┃ b                ┃
┡━━━━━━━╇━━━━━━━━━━━━━━━━━━┩
│ int64 │ string           │
├───────┼──────────────────┤
│     1 │ {"key": "value"} │
│     2 │ {"key": "value"} │
│     3 │ {"key": "value"} │
└───────┴──────────────────┘

[ins] In [19]: t.mutate(c=t.b.cast('json'))
Out[19]: 
┏━━━━━━━┳━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━┓
┃ a     ┃ b                ┃ c                    ┃
┡━━━━━━━╇━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━┩
│ int64 │ string           │ json                 │
├───────┼──────────────────┼──────────────────────┤
│     1 │ {"key": "value"} │ {'key': 'value'}     │
│     2 │ {"key": "value"} │ {'key': 'value'}     │
│     3 │ {"key": "value"} │ {'key': 'value'}     │
└───────┴──────────────────┴──────────────────────┘

[felipeangelimvieira]

Thank you! But I think I was not clear in my question. The objective would be, for example, to create a json column with a new structure, and not by parsing a string column. For example, creating a new column of json type {"column_a" : t.a}.

[gforsyth]

Ah, ok, so something like

[ins] In [21]: t
Out[21]: 
┏━━━━━━━┓
┃ a     ┃
┡━━━━━━━┩
│ int64 │
├───────┤
│     1 │
│     2 │
│     3 │
└───────┘

[ins] In [22]: t.mutate(b=ibis.struct({'column_a': t.a}).cast('json'))
Out[22]: 
┏━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━┓
┃ a     ┃ b                    ┃
┡━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━┩
│ int64 │ json                 │
├───────┼──────────────────────┤
│     1 │ {'column_a': 1}      │
│     2 │ {'column_a': 2}      │
│     3 │ {'column_a': 3}      │
└───────┴──────────────────────┘

?

[felipeangelimvieira]

Yes! Thank you