{

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


This tutorial shows How to print array and vector data to console in Rust.

In Rust, {} is used display trait to display the normal string. display trait is not implemented for Array and Vector.

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)

{} works only with strings of data in the println macro

Then how do you print the array or vector to the console?

{:?} or {vector or array:?} is used to print the data to the console whose data type implements 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?

Created a 2d vector and iterated using iter() and printed using debug trait for each nested vector element.

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);
    })
}
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