Bug report

Bug description:

Printing the empty string in a loop seems to cause memory use of Python to grow without bound.

while True:
    print('', end='')

or

import sys
while True:
    sys.stdout.write('')

The latter apparently does not work in interactive mode.

Relatedly,

while True:
    for _ in range(10**8):
        print('', end='')
    print()

causes memory use to grow to about 1.5GB and then reset when the newline is printed.

CPython versions tested on:

3.14, 3.11, 3.13

Operating systems tested on:

Linux

Linked PRs

• gh-151814: Fix unbounded memory growth from repeated empty writes to io.TextIOWrapper #151817
• [3.15] gh-151814: Fix unbounded memory growth from repeated empty writes to io.TextIOWrapper (GH-151817) #152071
• [3.14] gh-151814: Fix unbounded memory growth from repeated empty writes to io.TextIOWrapper (GH-151817) #152072
• [3.13] gh-151814: Fix unbounded memory growth from repeated empty writes to io.TextIOWrapper (GH-151817) #152073
• gh-151814: Add test for TextIOWrapper.write unbounded memory growth from repeated writes #152244