tracking version during run

[Skaperen]

suppose there is a Python script that intends to be run if the host has a version at or above a specific version X.Y. suppose the host also has an older version of Python. the script is complicated and needs to run some of its files under new process instances of Python. suppose the host does not have exact version X.Y but does have both an older one and a newer one. how can i be sure the version newer than X.Y is always run (i did not create the scripts)?