# Checking for system version import sys major, minor, bugfix = sys.version_info[:3] if major < 2: sys.exit('Python 2 is required') def defined(name): # LBYL (Look Before You Leap) return name in globals() or name in locals() or name in vars(__builtins__) def defined2(name): # EAFP (Easier to Ask Forgiveness than Permission) try: eval(name) return True except NameError: return False if defined('bloop') and defined('abs') and callable(abs): print abs(bloop) if defined2('bloop') and defined2('abs') and callable(abs): print abs(bloop)