来自Magnus Lycka在邮件列表上的回答:

You can skip buffering for a whole python process using python -u or by setting the environment variable PYTHONUNBUFFERED. You could also replace sys.stdout with some other stream like wrapper which does a flush after every call. class Unbuffered(object): def __init__(self, stream): self.stream = stream def write(self, data): self.stream.write(data) self.stream.flush() def writelines(self, datas): self.stream.writelines(datas) self.stream.flush() def __getattr__(self, attr): return getattr(self.stream, attr) import sys sys.stdout = Unbuffered(sys.stdout) print 'Hello'

def disable_stdout_buffering():
    # Appending to gc.garbage is a way to stop an object from being
    # destroyed.  If the old sys.stdout is ever collected, it will
    # close() stdout, which is not good.
    gc.garbage.append(sys.stdout)
    sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)

# Then this will give output in the correct order:
disable_stdout_buffering()
print "hello"
subprocess.call(["echo", "bye"])

不拯救旧的系统。Stdout, disable_stdout_buffering()不是幂等的，多次调用将导致这样的错误:

Traceback (most recent call last):
  File "test/buffering.py", line 17, in <module>
    print "hello"
IOError: [Errno 9] Bad file descriptor
close failed: [Errno 9] Bad file descriptor

另一种可能性是:

def disable_stdout_buffering():
    fileno = sys.stdout.fileno()
    temp_fd = os.dup(fileno)
    sys.stdout.close()
    os.dup2(temp_fd, fileno)
    os.close(temp_fd)
    sys.stdout = os.fdopen(fileno, "w", 0)

(附加到gc。垃圾并不是一个好主意，因为它是放置不可释放循环的地方，您可能需要检查它们。)

重写sys的只写方法是可能的。带有一个调用flush的Stdout。建议的方法实现如下所示。

def write_flush(args, w=stdout.write):
    w(args)
    stdout.flush()

w参数的默认值将保留原来的写入方法引用。定义了write_flush之后，可能会覆盖原来的写操作。

stdout.write = write_flush

代码假设stdout是从sys import stdout以这种方式导入的。

# reopen stdout file descriptor with write mode
# and 0 as the buffer size (unbuffered)
import io, os, sys
try:
    # Python 3, open as binary, then wrap in a TextIOWrapper with write-through.
    sys.stdout = io.TextIOWrapper(open(sys.stdout.fileno(), 'wb', 0), write_through=True)
    # If flushing on newlines is sufficient, as of 3.7 you can instead just call:
    # sys.stdout.reconfigure(line_buffering=True)
except TypeError:
    # Python 2
    sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)

工作人员:“塞巴斯蒂安”，在Python邮件列表的某个地方。

以下代码适用于Python 2.6、2.7和3.2:

import os
import sys
buf_arg = 0
if sys.version_info[0] == 3:
    os.environ['PYTHONUNBUFFERED'] = '1'
    buf_arg = 1
sys.stdout = os.fdopen(sys.stdout.fileno(), 'a+', buf_arg)
sys.stderr = os.fdopen(sys.stderr.fileno(), 'a+', buf_arg)

是的，默认启用。当调用python时，可以在命令行上使用-u选项禁用它。