Here's a naive solution of what I want to do using map_elements
. How can I do this with only Polars functions?
import polars as pl
# Create a DataFrame with a column containing lists of strings
df = pl.DataFrame({
"list_of_strings": [["a", "b", "c"], ["d", "e", "f"], ["g", "h", "i"]]
})
# Define a function to concatenate lists of strings into a single string
def concatenate_list_of_strings(lst):
return "".join(lst)
# Apply the function to the DataFrame
df = df.with_column(
pl.col("list_of_strings").map_elements(concatenate_list_of_strings, return_dtype=pl.String).alias("concatenated_string")
)
print(df)
As already mentioned in the comments, there is pl.Expr.list.join
in polars' native expression API to join all string items in a sublist with a separator between them.
df.with_columns(
pl.col("list_of_strings").list.join("")
)
shape: (3, 1)
┌─────────────────┐
│ list_of_strings │
│ --- │
│ str │
╞═════════════════╡
│ abc │
│ def │
│ ghi │
└─────────────────┘