What is StringIO in python used for in reality?

Question

I am not a pro and I have been scratching my head over understanding what exactly StringIO is used for. I have been looking around the internet for some examples. However, almos

Answer 1

I've just used StringIO in practice for two things:

• To unit-test a script that does a lot of printing, by redirecting sys.stdout to a StringIO instance for easy analysis;
• To create a guaranteed well-formed XML document (a custom API request) using ElementTree and then write it for sending via a HTTP connection.

Not that you need StringIO often, but sometimes it's pretty useful.

Answer 2

Here's a concrete example of a use case for StringIO: writing some data directly to aws s3, without needing to create a file on local disk:

import csv
import io
import boto3

data = [
    ["test", "data", "headers etc", "123","",],
    ["blah", "123", "35", "blah","",],
    ["abc", "def", "blah", "yep", "blah"]
]

bucket_name = 'bucket_name_here'
session = boto3.Session(
    aws_access_key_id = "fake Access ID"),
    aws_secret_access_key = "fake Secret key"),
    region_name = "ap-southeast-2")
)
s3 = session.resource('s3')
with io.StringIO() as f:
    writer = csv.writer(f, delimiter=",")
    writer.writerows(data)
    resp = s3.Object(bucket_name, "test.csv").put(Body=f.getvalue())

Enjoy your new csv on S3, without having written anything to your local disk!