[lcvriend]

If by "vectorized" you mean: "able to delegate the task of performing mathematical operations on the array's contents to optimized, compiled C code." then I do not think you are correct (unless perhaps you are supplying map with a dict or Series).

Series.map is not compiling your lambda's to C and running it. If there is a built-in method available it usually will be faster. Notable exception are pandas str methods which devolve into Python code but generally with more overhead than map/apply.

[oneoff786]

I mean not writing your own loops. A built in function is indeed better. But usually not what you need. And also, readability > speed when the execution time is trivial, which is it probably should be for pandas scale data.