*Created originally on Bitbucket by [cgsv (Victor Chen)](https://bitbucket.org/%7B1235c03c-3476-44ab-91da-03f83c8ed192%7D/)* In current version(2.5.11), I've found that [openpyxl/compat/__init__.py](https://bitbucket.org/openpyxl/openpyxl/src/6f966d4852dfa8fad0433fe347671faebb93bf64/openpyxl/compat/__init__.py#lines-59) may cause memory leakage when using Python 2.7. In line 59 ``` #!python warnings.simplefilter('default', DeprecationWarning) ``` This line will be executed every time a deprecated function is called. But unfortunately python 2.7 will simply append this deprecation type to a global list without checking for duplicates (python 3.x will check for it anyhow). So this will be an issue for those who are using 2.7. I think It is better to move this line outside the function or only execute it once when started.