How can I truncate sys.stderr due to exception handling?
import sys
try:
sys.stderr.write('Someone written here')
raise Exception
except:
# would like to clean sys.stderr here
sys.stderr.write('I only want this')
sys.exit(1)
I would like standard error to contains only the string "I only want this"
Would something like this help you? It would only work if you had only printed a single line to stderr so far: Python - Remove and Replace Printed items
The other way to do it would just be to append stderr to a string and print it in a finally, though this would not allow you to print incrementally in real time.
import sys
stderr_str = ''
try:
stderr_str += 'Someone written here'
raise Exception
except:
# would like to clean sys.stderr here
stderr_str = ''
stderr_str += 'I only want this'
finally:
sys.stderr.write(stderr_str)
Edit: You could also try redefining stderr to a file-like object, as is detailed in this answer. This should work even if third part modules write to stderr.
Example:
bash-3.2$ ls
a.py b.py
bash-3.2$ cat a.py
import sys
import b
sys.stderr = open('stderr.log', 'a')
b.raise_exception()
bash-3.2$ cat b.py
def raise_exception():
return 1/0
bash-3.2$ python a.py
bash-3.2$ ls
a.py b.py b.pyc stderr.log
bash-3.2$ cat stderr.log
Traceback (most recent call last):
File "a.py", line 5, in <module>
b.raise_exception()
File "/Users/username/tmp2/b.py", line 2, in raise_exception
return 1/0
ZeroDivisionError: integer division or modulo by zero
You could basically use a technique like this to capture all the stderr until the end, and then either write it to stderr, or just ignore it and write your new output to stderr.
