Why text I/O must be buffered in python 3?

Question

Python 2 supported unbuffered text I/O.

The same approach doesn't work in python 3. Why was unbuffered text I/O disabled?

> import sys > sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0) builtins.ValueError: can't have unbuffered text I/O 

The binary still works fine:

> sys.stdout = os.fdopen(sys.stdout.fileno(), 'wb', 0) # works fine 

Answer 1

This is an open bug, issue # 17404 (last update 2013-03-13): http://bugs.python.org/issue17404

Answer 2

For text files, if you want to use the buffering line-by-line, use open(..., buffering=1)

From python documentation:

1 to select line buffering (only usable in text mode)