All columns to uppercase in a DataFrame?

Question

Suppose there are hundreds of columns in a DataFrame. Some of the column names are in lower and some are in upper case.

Now, I want to convert all the columns to upper case.

import polars as pl

df = pl.DataFrame({
    "foo": [1, 2, 3, 4, 5, 8],
    "baz": [5, 4, 3, 2, 1, 9],
    
})

What I tried:

df.columns = [x.upper() for x in df.columns]

It worked, but is there any other way preferably without a for loop?

Answer 1

.rename() also accepts a Callable.

df.rename(str.upper)

shape: (6, 2)
┌─────┬─────┐
│ FOO ┆ BAZ │
│ --- ┆ --- │
│ i64 ┆ i64 │
╞═════╪═════╡
│ 1   ┆ 5   │
│ 2   ┆ 4   │
│ 3   ┆ 3   │
│ 4   ┆ 2   │
│ 5   ┆ 1   │
│ 8   ┆ 9   │
└─────┴─────┘