温温酱
的确有contextlib.redirect_stdout()功能在Python3.4中：from contextlib import redirect_stdoutwith open('help.txt', 'w') as f:
with redirect_stdout(f):
print('it now prints to `help.text`')它类似于：import sysfrom contextlib import contextmanager@contextmanagerdef redirect_stdout(new_target):
old_target, sys.stdout = sys.stdout, new_target # replace sys.stdout
try:
yield new_target # run some code with the replaced stdout
finally:
sys.stdout = old_target # restore to the previous value可以在早期的Python版本上使用。后一版本不是可重复使用..如果想要的话，可以做一个。它不会在文件描述符级别重定向stdout，例如：import osfrom contextlib import redirect_stdout
stdout_fd = sys.stdout.fileno()with open('output.txt', 'w') as f, redirect_stdout(f):
print('redirected to a file')
os.write(stdout_fd, b'not redirected')
os.system('echo this also is not redirected')b'not redirected'和'echo this also is not redirected'不重定向到output.txt档案。若要在文件描述符级别重定向，os.dup2()可用于：import osimport sysfrom contextlib import contextmanagerdef fileno(file_or_fd):
fd = getattr(file_or_fd, 'fileno', lambda: file_or_fd)()
if not isinstance(fd, int):
raise ValueError("Expected a file (`.fileno()`) or a file descriptor")
return fd@contextmanagerdef stdout_redirected(to=os.devnull, stdout=None):
if stdout is None:
stdout = sys.stdout
stdout_fd = fileno(stdout)
# copy stdout_fd before it is overwritten
#NOTE: `copied` is inheritable on Windows when duplicating a standard stream
with os.fdopen(os.dup(stdout_fd), 'wb') as copied:
stdout.flush() # flush library buffers that dup2 knows nothing about
try:
os.dup2(fileno(to), stdout_fd) # $ exec >&to
except ValueError: # filename
with open(to, 'wb') as to_file:
os.dup2(to_file.fileno(), stdout_fd) # $ exec > to
try:
yield stdout # allow code to be run with the redirected stdout
finally:
# restore stdout to its previous value
#NOTE: dup2 makes stdout_fd inheritable unconditionally
stdout.flush()
os.dup2(copied.fileno(), stdout_fd) # $ exec >&copied如果stdout_redirected()被使用，而不是redirect_stdout():import osimport sys
stdout_fd = sys.stdout.fileno()with open('output.txt', 'w') as f, stdout_redirected(f):
print('redirected to a file')
os.write(stdout_fd, b'it is redirected now\n')
os.system('echo this is also redirected')print('this is goes back to stdout')以前在stdout上打印的输出现在转到output.txt只要stdout_redirected()上下文管理器处于活动状态。注：stdout.flush()不刷新Python 3上的C Stdio缓冲区，其中I/O是直接在Python 3上实现的read()/write()系统呼叫。要刷新所有打开的C Stdio输出流，可以调用libc.fflush(None)如果某些C扩展使用基于Stdio的I/O，则显式地：try:
import ctypes from ctypes.util import find_libraryexcept ImportError:
libc = Noneelse:
try:
libc = ctypes.cdll.msvcrt # Windows
except OSError:
libc = ctypes.cdll.LoadLibrary(find_library('c'))def flush(stream):
try:
libc.fflush(None)
stream.flush()
except (AttributeError, ValueError, IOError):
pass # unsupported你可以用stdout参数来重定向其他流，而不仅仅是sys.stdout例如，合并sys.stderr和sys.stdout:def merged_stderr_stdout(): # $ exec 2>&1
return stdout_redirected(to=sys.stdout, stdout=sys.stderr)例子：from __future__ import print_functionimport syswith merged_stderr_stdout():
print('this is printed on stdout')
print('this is also printed on stdout', file=sys.stderr)注：stdout_redirected()混合缓冲I/O(sys.stdout(通常)和未缓冲的I/O(直接对文件描述符的操作)。小心，可能会有缓冲 问题.要回答，您的编辑：您可以使用python-daemon若要守护脚本并使用logging模块(AS)@erikb 85建议)而不是print语句，并仅重定向长期运行的Python脚本的stdout。nohup现在。