[New-bugs-announce] [issue6750] threading issue in __builtins__.print

[Jackson Yang]

New submission from Jackson Yang <jackson.yang at augmentum.com>:

# Bug Description
In a multi-threaded environment, the Win32 Python3000 built-in function
"print" may give the output several times.

# How to Reproduce:
import threading
event = threading.Event()
class Test(threading.Thread):
    def __init__(self, ord):
        super().__init__()
        self.ord = ord
    def run(self):
        event.wait()
        print('Hello, world!', self.ord)
threads = tuple(map(Test, range(8)))
tuple(map(lambda thread: thread.start(), threads))
event.set()
tuple(map(lambda thread: thread.join(), threads))
# EOF

# Problem Observed
[The first run, 0 is doubled]
Hello, world! 0
Hello, world! 0
Hello, world! 1
Hello, world! 2
Hello, world! 3
Hello, world! 4
Hello, world! 5
Hello, world! 6
Hello, world! 7

[the second run, 1 and 7 are doubled]
Hello, world! 1
Hello, world! 1
Hello, world! 2
Hello, world! 3
Hello, world! 4
Hello, world! 5
Hello, world! 6
Hello, world! 7
Hello, world! 7
Hello, world! 0

# Expected Result
Each thread gives ONE AND ONLY ONE output.
OR
State this as The Expected Behavior, document it and ask the user to
write something such as critical section.

----------
components: IO
messages: 91807
nosy: nullnil
severity: normal
status: open
title: threading issue in __builtins__.print
type: behavior
versions: Python 3.1

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue6750>
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