How to flush StringIO() in python 2.7?

Question

I am trying to redirect output, and flush every once in a while to clear the buffer.

Flushing doesn't do anything - can't even enter the function with debugger.

from io import BytesIO as StringIO

out = StringIO()
out.write("hi")
output = out.getvalue().strip()
assert output == "hi"
out.flush()
output = out.getvalue().strip()
assert output == ""

The second assertion fails, as output is still "hi". flush() did nothing.

What am I getting wrong?

Chirag Kalal · Accepted Answer · 2019-05-13T07:04:54.727

1

Just do one change, Replace out.flush() with out.truncate(0) and then it will be work fine as follows:

from io import BytesIO as StringIO

out = StringIO()
out.write("hi")
output = out.getvalue().strip()
assert output == "hi"
out.seek(0)
out.truncate(0)
output = out.getvalue().strip()
assert output == ""

edited May 13 '19 at 07:04

answered May 13 '19 at 06:53

Chirag Kalal

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1

Having read the duplicate, For future compatibility best to also `out.seek(0)` before `.truncate(0)` – Gulzar May 13 '19 at 06:59
Yeah, It will be perfect. – Chirag Kalal May 13 '19 at 07:01
edit your answer please so I will accept – Gulzar May 13 '19 at 07:03

How to flush StringIO() in python 2.7?

1 Answers1