Read the book copyright statement and license. Some books have separate license for examples. However, if you copy an example from a book into a code, then ver

Read the book copyright statement and license. Some books have separate license for examples. However, if you copy an example from a book into a code, then very often it's fair use, but if you copy the same example from a book into your own book, then very often it's a copyright infringement, unless explicitly allowed by the book license.