In some fields, Python is embedded as an interpreter into major binary platforms or commercial apps. So in many of these cases the end user doesn't have a choi

In some fields, Python is embedded as an interpreter into major binary platforms or commercial apps. So in many of these cases the end user doesn't have a choice to use Python 3 until it's on offer. And the vendor has usually integrated Python at a binary level into C code; that's why they provide a Python API. The answer could even be "Red Hat Enterprise Linux 6"; consider that Python 2 is the default in this OS, which ended official support only at the end of last year. Many enterprises _chose_ this platform for its longevity, along with 3rd party vendors of commercial software.