In Rust, how to use variable in format! macro?

Question

I have a very simple program:

fn main() { let y = format!("{:0>3}", 11); println!("{}", y); }

The output is the string 011. The problem is that the width specifier 3 in {:0>3} is coming from a variable like this:

fn main() { let x = 3usize; let y = format!("{:0>3}", 11); println!("{}", y); }

How can I use variable x to replace 3 in {:0>3}?

Denys Séguret · Accepted Answer · 2021-06-19 05:05:58Z

fn main() { let x = 3; let y = format!("{:0>width$}", 11, width=x); println!("{}", y); }

As it may be hard to remember the whole formatting syntax, it's a good idea to get used to find the reference.

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