How to Print Array and Vector data to console in Rust?

How to Print Array and Vector data to console in Rust?

This tutorial demonstrates how to print array and vector data to the console in Rust.

In Rust,{} is typically used with the Display trait to print normal strings. However, the Display trait is not implemented for arrays and vectors.

fn main() {
    let vector = vec![5; 30];
    println!("{}", vector);
}

It throws error[E0277]: Vec<{integer}> doesn’t implement std::fmt::Display and Vec<{integer}> cannot be formatted with the default formatter

error[E0277]: `Vec<{integer}>` doesn't implement `std::fmt::Display`
 --> test.rs:3:20
  |
3 |     println!("{}", v2);
  |                    ^^ `Vec<{integer}>` cannot be formatted with the default formatter
  |
  = help: the trait `std::fmt::Display` is not implemented for `Vec<{integer}>`
  = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
  = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)

The {} placeholder works only with strings in the println macro. So, how do you print arrays or vectors to the console?

You can use {:?} or {vector or array:?} to print data to the console whose data type implements the Debug trait.

fn main() {
    let vector = vec![1, 2, 3, 4, 5]; // vector of integer
    let array = ["one", "two", "three", "four", "five"]; // array of strings

    println!("{:?}", vector);
    println!("{vector:?}");
    println!("{:?}", array);
    println!("{array:?}");

}

Output:

[1, 2, 3, 4, 5]
[1, 2, 3, 4, 5]
["one", "two", "three", "four", "five"]
["one", "two", "three", "four", "five"]

How to Print 2D Vector in Rust?

You can create a 2D vector and iterate over it using iter() and then print each nested vector element using the Debug trait.

Here is a Rust 2d Vector with an example

fn main() {

    let mut vector_2d: Vec<Vec<i32>> = Vec::new();

    2d_vector = vec![
        vec![1,2,3],
        vec![4,5,6],
        vec![7,8,9]
    ];

    vector_2d.iter().for_each(|it| {
             println!("{:#?}", it);
    })
}

This prints each nested vector element.