如何输出到控制台和文件？

Question

我试图在python中找到一种方法将脚本执行日志重定向到文件以及stdoutpythonic方式.有没有简单的方法来实现这一目标？

Answer 1

使用日志记录模块(http://docs.python.org/library/logging.html):

import logging

logger = logging.getLogger('scope.name')

file_log_handler = logging.FileHandler('logfile.log')
logger.addHandler(file_log_handler)

stderr_log_handler = logging.StreamHandler()
logger.addHandler(stderr_log_handler)

# nice output format
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
file_log_handler.setFormatter(formatter)
stderr_log_handler.setFormatter(formatter)

logger.info('Info message')
logger.error('Error message')

Answer 2

我想出了这个[未经测试]

import sys

class Tee(object):
    def __init__(self, *files):
        self.files = files
    def write(self, obj):
        for f in self.files:
            f.write(obj)
            f.flush() # If you want the output to be visible immediately
    def flush(self) :
        for f in self.files:
            f.flush()

f = open('out.txt', 'w')
original = sys.stdout
sys.stdout = Tee(sys.stdout, f)
print "test"  # This will go to stdout and the file out.txt

#use the original
sys.stdout = original
print "This won't appear on file"  # Only on stdout
f.close()

print>>xyz在python中期望一个write()函数xyz.您可以使用自己的自定义对象.或者,您也可以让sys.stdout引用您的对象,在这种情况下即使没有它也将进行编辑>>xyz.

Answer 3

我只想建立在Serpens的答案并添加一行:

logger.setLevel('DEBUG')

这将允许您选择记录的消息级别.

例如,在Serpens示例中,

logger.info('Info message')

不会被记录,因为它默认只记录警告及以上.

有关所用级别的更多信息,请参阅此处

Answer 4

可能是最短的解决方案：

def printLog(*args, **kwargs):
    print(*args, **kwargs)
    with open('output.out','a') as file:
        print(*args, **kwargs, file=file)

printLog('hello world')

向sys.stdout和写入“hello world” ，其output.out工作方式与 print() 完全相同。

Note: Please do not specify the file argument for the printLog function. Calls like printLog('test',file='output2.out') are not supported.

Answer 5

这是对 @UltraInstinct 的 Tee 类的一个小改进，修改为上下文管理器并捕获任何异常。

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()

要使用上下文管理器：

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