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

python stringio
simha picture simha · Jan 19, 2011 · Viewed 63.6k times · Source

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

When is StringIO used?

from io import StringIO


def meth1(string):
    a = []
    for i in range(100):
        a.append(string)
    return ''.join(a)

def meth2(string):
    a = StringIO()
    for i in range(100):
        a.write(string)
    return a.getvalue()


if __name__ == '__main__':
    from timeit import Timer
    string = "This is test string"
    print(Timer("meth1(string)", "from __main__ import meth1, string").timeit())
    print(Timer("meth2(string)", "from __main__ import meth2, string").timeit())

Results:

16.7872819901
18.7160351276

Answer

TryPyPy picture TryPyPy · Jan 19, 2011

The main advantage of StringIO is that it can be used where a file was expected. So you can do for example (for Python 2):

import sys
import StringIO

out = StringIO.StringIO()
sys.stdout = out
print "hi, I'm going out"
sys.stdout = sys.__stdout__
print out.getvalue()

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