如何使用脚本将标准输出重定向到文件和控制台？

Question

我想运行一个 python 脚本并在文本文件中捕获输出，并希望在控制台上显示。

我想将它指定为 python 脚本本身的属性。不要每次都在命令提示符下使用命令echo "hello world" | tee test.txt。

在我尝试过的脚本中：

sys.stdout = open('log.txt','w')

但这不会在屏幕上显示标准输出。

我听说过日志记录模块，但我无法使用该模块来完成这项工作。

Answer 1

您可以在执行 Python 文件时使用 shell 重定向：

python foo_bar.py > file

这会将打印在标准输出上的所有结果从 Python 源文件写入日志文件。

或者如果你想从脚本中记录：

import sys

class Logger(object):
    def __init__(self):
        self.terminal = sys.stdout
        self.log = open("logfile.log", "a")
   
    def write(self, message):
        self.terminal.write(message)
        self.log.write(message)  

    def flush(self):
        # this flush method is needed for python 3 compatibility.
        # this handles the flush command by doing nothing.
        # you might want to specify some extra behavior here.
        pass    

sys.stdout = Logger()

现在你可以使用了：

print "Hello"

这会将“Hello”写入标准输出和日志文件。

Answer 2

我可以同时将输出重定向到控制台和文本文件：

te = open('log.txt','w')  # File where you need to keep the logs

class Unbuffered:

   def __init__(self, stream):

       self.stream = stream

   def write(self, data):

       self.stream.write(data)
       self.stream.flush()
       te.write(data)    # Write the data of stdout here to a text file as well



sys.stdout=Unbuffered(sys.stdout)

Answer 3

使用日志模块来调试和关注您的应用

这是我如何设法记录到文件和控制台/标准输出

import logging
logging.basicConfig(level=logging.INFO,
                    format='%(asctime)s - %(levelname)s - %(message)s',
                    filename='logs_file',
                    filemode='w')
# Until here logs only to file: 'logs_file'

# define a new Handler to log to console as well
console = logging.StreamHandler()
# optional, set the logging level
console.setLevel(logging.INFO)
# set a format which is the same for console use
formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
# tell the handler to use this format
console.setFormatter(formatter)
# add the handler to the root logger
logging.getLogger('').addHandler(console)

# Now, we can log to both ti file and console
logging.info('Jackdaws love my big sphinx of quartz.')
logging.info('Hello world')

从源代码阅读： https://docs.python.org/2/howto/logging-cookbook.html

Answer 4

基于Amith Koujalgi's answer，这是一个可用于日志记录的简单模块 -

transcript.py：

"""
Transcript - direct print output to a file, in addition to terminal.

Usage:
    import transcript
    transcript.start('logfile.log')
    print("inside file")
    transcript.stop()
    print("outside file")
"""

import sys

class Transcript(object):

    def __init__(self, filename):
        self.terminal = sys.stdout
        self.logfile = open(filename, "a")

    def write(self, message):
        self.terminal.write(message)
        self.logfile.write(message)

    def flush(self):
        # this flush method is needed for python 3 compatibility.
        # this handles the flush command by doing nothing.
        # you might want to specify some extra behavior here.
        pass

def start(filename):
    """Start transcript, appending print output to given filename"""
    sys.stdout = Transcript(filename)

def stop():
    """Stop transcript and return print functionality to normal"""
    sys.stdout.logfile.close()
    sys.stdout = sys.stdout.terminal

Answer 5

我设计了一个更简单的解决方案。只需定义一个将打印到文件或屏幕或两者的函数。在下面的示例中，我允许用户输入输出文件名作为参数，但这不是强制性的：

OutputFile= args.Output_File
OF = open(OutputFile, 'w')

def printing(text):
    print text
    if args.Output_File:
        OF.write(text + "\n")

在此之后，将一行打印到文件和/或屏幕所需的只是： 打印（Line_to_be_printed）

Answer 6

from IPython.utils.io import Tee
from contextlib import closing

print('This is not in the output file.')        

with closing(Tee("outputfile.log", "w", channel="stdout")) as outputstream:
    print('This is written to the output file and the console.')
    # raise Exception('The file "outputfile.log" is closed anyway.')
print('This is not written to the output file.')   

# Output on console:
# This is not in the output file.
# This is written to the output file and the console.
# This is not written to the output file.

# Content of file outputfile.txt:
# This is written to the output file and the console.

IPython.utils.io 中的 Tee 类可以满足您的需求，但它缺少在 with 语句中调用它所需的 __enter__ 和 __exit__ 方法。这些是contextlib.closing添加的。

Answer 7

这是一个简单的上下文管理器，它打印到控制台并将相同的输出写入文件。它还会将任何异常写入文件。

import traceback
import sys

# Context manager that copies stdout and any exceptions to a log file
class Tee(object):
    def __init__(self, filename):
        self.file = open(filename, 'w')
        self.stdout = sys.stdout

    def __enter__(self):
        sys.stdout = self

    def __exit__(self, exc_type, exc_value, tb):
        sys.stdout = self.stdout
        if exc_type is not None:
            self.file.write(traceback.format_exc())
        self.file.close()

    def write(self, data):
        self.file.write(data)
        self.stdout.write(data)

    def flush(self):
        self.file.flush()
        self.stdout.flush()

使用上下文管理器：

print("Print")
with Tee('test.txt'):
    print("Print+Write")
    raise Exception("Test")
print("Print")

Answer 8

我在这里尝试了一些解决方案，但没有找到同时写入文件和控制台的解决方案。所以这就是我所做的(based on this answer)

class Logger(object):
    def __init__(self):
        self.terminal = sys.stdout

    def write(self, message):
        with open ("logfile.log", "a", encoding = 'utf-8') as self.log:            
            self.log.write(message)
        self.terminal.write(message)

    def flush(self):
        #this flush method is needed for python 3 compatibility.
        #this handles the flush command by doing nothing.
        #you might want to specify some extra behavior here.
        pass
sys.stdout = Logger()   

此解决方案使用更多的计算能力，但可靠地将所有数据从标准输出保存到记录器文件中，并且使用更少的内存。为了我的需要，我还在 self.log.write(message) 中添加了时间戳。效果很好。

Answer 9

这种方式在我的情况下非常有效。我只是根据这个线程中提供的其他代码添加了一些修改。

import sys, os 

orig_stdout = sys.stdout  # capture original state of stdout

te = open('log.txt','w')  # File where you need to keep the logs

class Unbuffered:
   def __init__(self, stream):
       self.stream = stream

   def write(self, data):
       self.stream.write(data)
       self.stream.flush()
       te.write(data)    # Write the data of stdout here to a text file as well

sys.stdout=Unbuffered(sys.stdout)




#######################################
##  Feel free to use print function  ##
#######################################

print("Here is an Example =)")

#######################################
##  Feel free to use print function  ##
#######################################




# Stop capturing printouts of the application from Windows CMD
sys.stdout = orig_stdout  # put back the original state of stdout
te.flush()  # forces python to write to file
te.close()  # closes the log file

# read all lines at once and capture it to the variable named sys_prints
with open('log.txt', 'r+') as file:
    sys_prints = file.readlines() 

# erase the file contents of log file
open('log.txt', 'w').close()

Answer 10

要将输出重定向到文件和终端而不修改 Python 脚本在外部的使用方式，您可以使用 pty.spawn(itself):

#!/usr/bin/env python
"""Redirect stdout to a file and a terminal inside a script."""
import os
import pty
import sys

def main():
    print('put your code here')

if __name__=="__main__":
    sentinel_option = '--dont-spawn'
    if sentinel_option not in sys.argv:
        # run itself copying output to the log file
        with open('script.log', 'wb') as log_file:
            def read(fd):
                data = os.read(fd, 1024)
                log_file.write(data)
                return data

            argv = [sys.executable] + sys.argv + [sentinel_option]
            rc = pty.spawn(argv, read)
    else:
        sys.argv.remove(sentinel_option)
        rc = main()
    sys.exit(rc)

如果pty 模块不可用（在 Windows 上），那么您可以将其替换为更便携的teed_call() function，但它提供普通管道而不是伪终端——它可能会改变某些程序的行为。

基于pty.spawn 和subprocess.Popen 的解决方案与将sys.stdout 替换为类似文件的对象相比的优势在于，它们可以在文件描述符级别捕获输出，例如，如果脚本启动其他进程也可以在 stdout/stderr 上产生输出。请参阅我对相关问题的回答：Redirect stdout to a file in Python?

Answer 11

基于Brian Burns edited answer，我创建了一个更容易调用的单个类：

class Logger(object):

    """
    Class to log output of the command line to a log file

    Usage:
    log = Logger('logfile.log')
    print("inside file")
    log.stop()
    print("outside file")
    log.start()
    print("inside again")
    log.stop()
    """

    def __init__(self, filename):
        self.filename = filename

    class Transcript:
        def __init__(self, filename):
            self.terminal = sys.stdout
            self.log = open(filename, "a")
        def __getattr__(self, attr):
            return getattr(self.terminal, attr)
        def write(self, message):
            self.terminal.write(message)
            self.log.write(message)
        def flush(self):
            pass

    def start(self):
        sys.stdout = self.Transcript(self.filename)

    def stop(self):
        sys.stdout.log.close()
        sys.stdout = sys.stdout.terminal

Answer 12

根据@Arnold Suiza 的回答，这里有一个函数，您可以在开始时运行一次，然后将所有内容立即打印到标准输出和文件：

def print_to_file(filename):
    orig_stdout = sys.stdout  # capture original state of stdout

    class Unbuffered:
        def __init__(self, filename):
            self.stream = orig_stdout
            self.te = open(filename,'w')  # File where you need to keep the logs

        def write(self, data):
            self.stream.write(data)
            self.stream.flush()
            self.te.write(data)    # Write the data of stdout here to a text file as well
            self.te.flush()

    sys.stdout=Unbuffered(filename)

现在只需在程序启动时运行 print_to_file('log.txt') 就可以了！

Answer 13

我试过了：

"""
Transcript - direct print output to a file, in addition to terminal.

Usage:
    import transcript
    transcript.start('logfile.log')
    print("inside file")
    transcript.stop()
    print("outside file")
"""

import sys

class Transcript(object):

    def __init__(self, filename):
        self.terminal = sys.stdout, sys.stderr
        self.logfile = open(filename, "a")

    def write(self, message):
        self.terminal.write(message)
        self.logfile.write(message)

    def flush(self):
        # this flush method is needed for python 3 compatibility.
        # this handles the flush command by doing nothing.
        # you might want to specify some extra behavior here.
        pass

def start(filename):
    """Start transcript, appending print output to given filename"""
    sys.stdout = Transcript(filename)

def stop():
    """Stop transcript and return print functionality to normal"""
    sys.stdout.logfile.close()
    sys.stdout = sys.stdout.terminal
    sys.stderr = sys.stderr.terminal

Answer 14

您可以使用带有 print rint 的“chevron”语法的 >> python 将输出重定向到文件，如docs中所示

让我们看看，

fp=open('test.log','a')   # take file  object reference 
print >> fp , "hello world"            #use file object with in print statement.
print >> fp , "every thing will redirect to file "
fp.close()    #close the file 

签出文件 test.log 你会得到数据 并在控制台上打印只需使用 plain print 语句。