Good piece. A (minor) nitpick. On section titled '''Prefer "pure" functions and generators''' two "dedupe" functions are shown. They are stated to be the same

Good piece. A (minor) nitpick. On section titled '''Prefer "pure" functions and generators''' two "dedupe" functions are shown. They are stated to be the same but aren't. The first function returns the number of duplicated elements excluded (an int). The second function returns a set of excluding duplicated elements. It's true (in the first function) that the original list "items" will be modified to exclude the duplicated elements but an additional unshown step is needed in the second to determine the number... i.e len(items) - len(set(items)).