How to get number of columns in a rust-polars DataFrame

Question

I have the following dataframe

use polars::prelude::*;

fn main() {
    let df = df!("1" => &[1, 2, 3, 4, 5,6], "2" => &[2, 3, 4, 5, 6, 6]);
    println!("{}", df.unwrap());
}

shape: (6, 2)
┌─────┬─────┐
│ 1   ┆ 2   │
│ --- ┆ --- │
│ i32 ┆ i32 │
╞═════╪═════╡
│ 1   ┆ 2   │
│ 2   ┆ 3   │
│ 3   ┆ 4   │
│ 4   ┆ 5   │
│ 5   ┆ 6   │
│ 6   ┆ 6   │
└─────┴─────┘

How can I retrieve the number of columns in df(In this case it's 2)?

Answer 1

There are multiple ways to do this.

1. The easiest way is to call the .width method which returns the number of columns.
2. You can call the get_column_names() to get the column names as vector, and then call it's len method.
3. You can also call the .shape method to get the tuple (no_of_rows, no_of_columns) and access the second element.

use polars::prelude::*;

fn main() {
    let df = df!("1" => &[1, 2, 3, 4, 5,6], "2" => &[2, 3, 4, 5, 6, 6]).unwrap();
    println!("No of columns: {}", df.width());
    println!("No of columns: {}", df.get_column_names().len());
    println!("No of columns: {}", df.shape().1)
    // This will print: 
    // No of columns: 2
    // No of columns: 2
    // No of columns: 2
}