Creating a file without overwriting

Use mode "x" when an existing path should be an error. This check happens atomically during creation, so there is no separate existence-check race.

def demo() -> Result[(), IoError]:
    with open("new.txt", "x")? as file:
        file.write("first version")?
    print(read_text("new.txt")?)?
    Ok(())
def main() -> Result[(), IoError]:
    demo()?
    Ok(())

first version

Add + to an open mode to enable both reading and writing. r+ preserves an existing file, w+ truncates or creates, x+ creates exclusively, and a+ starts at EOF and always appends writes. Writes overwrite bytes at the current position; they do not insert characters. Use care with multibyte text.

def demo() -> Result[(), IoError]:
    write_text("update.txt", "hello")?
    with open("update.txt", "r+")? as file:
        file.read(1)?
        file.write("a")?
    print(read_text("update.txt")?)?
    Ok(())
def main() -> Result[(), IoError]:
    demo()?
    Ok(())

hallo