From the python wiki
The for statement is most commonly used. It loops over the elements of
a sequence, assigning each to the loop variable. If the body of your
loop is simple, the interpreter overhead of the for loop itself can be
a substantial amount of the overhead. This is where the map function
is handy. You can think of map as a for moved into C code.
So simple for loops have overhead that list comprehensions get away with.
