Comments (6)
for those who want a temporary solution, you can check if such column in the df.columns
array. then use with_columns
to add a column full of null
values
const data3 = [
{ col1: "b", col2: "d", str: "1 -> 1 -> 2", time: 1691565256703, col3: null },
{ col1: "b", col2: "c", str: "2 -> 2 -> 1", col3: null },
{ col1: "c", col2: "a", str: "3 -> 3 -> 3", col3: null },
];
let df3 = pl.DataFrame(data3 );
if (!df3.columns.includes('col3')) {
df3 = df3.withColumn(pl.lit(null).alias("col3"));
}
┌──────┬──────┬─────────────┬───────────┬──────┐
│ col1 ┆ col2 ┆ str ┆ time ┆ col3 │
│ --- ┆ --- ┆ --- ┆ --- ┆ --- │
│ str ┆ str ┆ str ┆ f64 ┆ null │
╞══════╪══════╪═════════════╪═══════════╪══════╡
│ b ┆ d ┆ 1 -> 1 -> 2 ┆ 1.6916e12 ┆ null │
│ b ┆ c ┆ 2 -> 2 -> 1 ┆ null ┆ null │
│ c ┆ a ┆ 3 -> 3 -> 3 ┆ null ┆ null │
└──────┴──────┴─────────────┴───────────┴──────┘
from nodejs-polars.
While looking into this one, I noticed that providing arrays into the object:
const lf = pl.DataFrame({ a: [1], b: [2], c: [null] });
console.log(lf);
returns
shape: (1, 3)
┌─────┬─────┬──────┐
│ a ┆ b ┆ c │
│ --- ┆ --- ┆ --- │
│ f64 ┆ f64 ┆ f64 │
╞═════╪═════╪══════╡
│ 1.0 ┆ 2.0 ┆ null │
└─────┴─────┴──────┘
Because of this notice of the documentation:
Interface DataFrame
A DataFrame is a two-dimensional data structure that represents data as a table with rows and columns.
ParamObject, Array, or Series Two-dimensional data in various forms. object must contain Arrays. Array may contain Series or other Arrays.
I am a little bit hesistant whether I should further check this?
from nodejs-polars.
It's probably not a high priority ticket as you've demonstrated a workaround. I am coming from pandas where the other syntax does work.
>>> pd.DataFrame([{'a':1, 'b':2, 'c':None}])
a b c
0 1 2 None
from nodejs-polars.
I have a created a PR for this issue.
from nodejs-polars.
But I do see a problem after my PR.
pl.DataFrame([{a:1, b:2, c:null}])
will omit column c, unless one of the rows has a non-null value.
from nodejs-polars.
But I do see a problem after my PR.
pl.DataFrame([{a:1, b:2, c:null}]) will omit column c, unless one of the rows has a non-null value.
I believe this is a known issue in the polars json parser. which the JS parser is mostly based off of.
from nodejs-polars.
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