> I don't understand why sqrt is not a built-in function. > Why do we have to first import the function from the math module? > I use it ALL THE TIME!
For one, it's specific to numeric types. You might use it all the time, but I (for example) almost never need to use it, or to import the math module for my Python work/play. OTOH, I use stuff from the sys and csv modules (and lately, pandas) all the time. I import those modules when necessary. If you don't need them, I suspect you might grumble that they are useless for you. Requiring explicit module import gives programmers more control over the content of their module namespaces if the builtins don't include the kitchen sink. If you skim the output of import builtins dir(builtins) you should see that the two largest classes of builtin identifiers are exceptions (ZeroDivisionError, etc) and types (list, set, etc). Other classes include singleton constants (True, False, None) and general sequence operations (useful for loop control - reversed, iter, zip...). math.sqrt doesn't fit into those object classes. The remainder are a mixture of things, but generally aren't quite as special purpose as that. Granted, there are a couple which might be better left out (IMO), like round and pow, but I suspect their presence might simply be more a matter of them being present since Python's earliest days and reflect a tendency later to avoid gratuitous breakage of existing code. Finally, should have never considered it, I think you might want to study the output of import this Think on the second and last lines in particular. Skip -- https://mail.python.org/mailman/listinfo/python-list
