Well, I think for a 9 year old it's fine. I think the stage where you would run into issues is when trying to get into "actual" software development, where the flexibility in scoping and typing afforded by Python can lead to some bad habits (e.g. overusing global/shared variables, declaring them from within functions, catching errors late instead of validating data first, ...)

I don't have a ton of experience with it but I think C# strikes a pretty good balance between strictness and beginner-friendliness. Modern Java isn't all that bad either, though it doesn't have very good options for fun things to build. But again, I don't think this necessarily applies to a child; I'm an educator at a university so both my target audience and point of reference are freshman compsci students.