python - 将所有标准输出存储到文件中，同时仍将其显示在屏幕上

Question

除了python，这里似乎有所有语言的问题/答案。 (至少我没找到)

从这个问题Redirect stdout to a file in Python?我了解到，为了将所有输出从屏幕重定向到一个文件，我只需要使用:

import sys

some_list = ['elem1', 'elem2']

for elem in some_list:

    sys.stdout = open(elem + '.log', 'w')

    # Do lots of stuff that print messages.
    print 'lots of stuff for', elem

print 'Code finished'

这会将所有输出存储到 elemx.log文件:

elem1.log
lots of stuff for elem1

elem2.log
lots of stuff for elem2
Code finished

关于这种方法我有两个问题:

1- 如何使最后一行打印行(即:Code finished)不存储在为最后一个 elem 创建的文件中？

2- 如何让存储的输出同时显示在屏幕上？

Answer 1

wrapper 很性感

import sys

class Logger(file):
    def __init__(self,*a,**kw):
        # copy original stdout to instance
        self.stdout = sys.stdout
        return super(Logger,self).__init__(*a,**kw)

    def write(self,data):
        self.stdout.write(data) # to screen
        return super(Logger,self).write(data) #to file

    def writelines(self,lines):
        for line in lines: self.write(line)

    def close(self):
        # return it back
        sys.stdout = self.stdout



some_list = ['elem1', 'elem2']

for elem in some_list:
    with Logger("/tmp/1/{}.log".format(elem), "w") as sys.stdout:
    # Do lots of stuff that print messages.
        print 'lots of stuff for', elem



print 'Code finished'

结果

$ python2 out.py 
Code finished
$ ls
elem1.log  elem2.log  out.py

很酷的副作用:

print 'this on screen'

with Logger("/tmp/1/main.log", "w") as sys.stdout:
     print 'this on screen an in main.log'

     with Logger("/tmp/1/sub.log", "w") as sys.stdout:
          print 'this on screen, in man.log and in sub.log'

print 'only on screen again'