What Is the Difference Between unwrap, expect, and the ? Operator?

Use unwrap to panic with a default message, expect to panic with a custom message, and the ? operator to propagate errors to the caller.

fn main() {
    let file = std::fs::File::open("hello.txt")
        .expect("Failed to open file: custom message");
    
    let contents = std::fs::read_to_string(&file)?;
    
    let value: Option<i32> = Some(42);
    let num = value.unwrap();
}

The ? operator requires the function to return a Result or Option type to propagate the error or None value automatically.

These are three ways to handle situations where code might fail. unwrap and expect crash your program immediately if something goes wrong, with expect letting you write a specific error note. The ? operator is like passing a problem up to your manager; it stops the current task and returns the error to the function that called you so they can decide what to do.