When is StringIO used, as opposed to joining a list of strings?

Question

Using StringIO as string buffer is slower than using list as buffer.

When is StringIO used?

from io import StringIO


def meth1(string):
    a = []
             


        

Answer 1

Well, I don't know if I would like to call that using it as a "buffer", you are just multiplying a string a 100 times, in two complicated ways. Here is an uncomplicated way:

def meth3(string):
    return string * 100

If we add that to your test:

if __name__ == '__main__':

    from timeit import Timer
    string = "This is test string"
    # Make sure it all does the same:
    assert(meth1(string) == meth3(string))
    assert(meth2(string) == meth3(string))
    print(Timer("meth1(string)", "from __main__ import meth1, string").timeit())
    print(Timer("meth2(string)", "from __main__ import meth2, string").timeit())
    print(Timer("meth3(string)", "from __main__ import meth3, string").timeit())

It turns out to be way faster as a bonus:

21.0300650597
22.4869811535
0.811429977417

If you want to create a bunch of strings, and then join them, meth1() is the correct way. There is no point in writing it to StringIO, which is something completely different, namely a string with a file-like stream interface.