Is this a PYTHON?? A shocking sight on a UK Riverbank

I found a LARGE PYTHON while doing some early season spate river fishing for Wild Brown Trout, on the Afon Lwyd in Pontypool Park, South Wales. This is definitely not something you expect to see in the Gwent Valleys! Was it a dumped pet, or did it escape into the wild? Thank you for watching, I appreciate it! Gareth #riversidewithme