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pythonexceptionatexit

finally versus atexit

I end up having to write and support short python wrapper scripts with the following high-level structure:

try:
    code
    ...
    ...
except:
    raise
finally:
    file_handle.close()
    db_conn.close()

Notice that all I do in the except block is re-raise the exception to the script caller sans window-dressing; this is not a problem in my particular context. The idea here is that cleanup code should always be executed by means of the finally block, exception or not.

Am I better off using an atexit handler for this purpose? I could do without the extra level of indentation introduced by try.

Solution

  • Just use contextlib.closing

    with closing(resource1) as f1, closing(resource2) as f2:
    f1.something()
    f2.something()

    And they will be automatically closed. Files objects can be used directly as contexts so you don't need the closing call.

    If close is not the only method used by your resources, you can create custom functions with the contextlib.contextmanager decorator.