On the one hand it’s annoying, on the other it enforces a discipline of thought in the same way that having to name variables does.

That’s an interesting principle, something like “a block of code that is complex enough to be written across multiple lines of code ought to be given a name,” but standard idiomatic Python already violates that principle by featuring multiple lines in the body of a for loop. The fact that the body of a for loop can be multiple lines but the “body” of a lambda cannot is an arbitrary syntax inconsistency.

    def b(x):
      return x + 1

vs

    x => x + 1