How to suppress py.test internal deprecation warnings

I think you do not want to hide all warnings, but just the ones that are not relevant. And in this case, deprectation warnings from imported python modules.

Having a read on pytest documentation about Warnings Capture:

Both -W command-line option and filterwarnings ini option are based on Python’s own -W option and warnings.simplefilter, so please refer to those sections in the Python documentation for other examples and advanced usage.

So you can filter warnings with python's -W option!

It seems that pytest completely removes filters, because it shows all those DeprecationWarning when running, and Python's documentation about Default Warning Filters clearly says:

In regular release builds, the default warning filter has the following entries (in order of precedence):

default::DeprecationWarning:__main__
ignore::DeprecationWarning
ignore::PendingDeprecationWarning
ignore::ImportWarning
ignore::ResourceWarning

So in your case, if you want let say to filter types of warning you want to ignore, such as those DeprecationWarning, just run the pytest command with -W option :

$ pytest path-to-test-folder -W ignore::DeprecationWarning

EDIT: From colini's comment, it is possible to filter by module. Example to ignore deprecation warnings from all sqlalchemy :

ignore::DeprecationWarning:sqlalchemy.*:

You can then list your installed modules that creates too much noise in the output of pytest

EDIT2: For more precise control, the Python documentation about Describing Warning Filters states that the general way to write such warning filters is:

action:message:category:module:line

Use with file rather than in command line:

You may prefer list those filters in pytest.ini file :

[pytest]
filterwarnings =
    ignore::DeprecationWarning

From pytest --help:

--disable-pytest-warnings
                      disable warnings summary, overrides -r w flag

pytest -p no:warnings, or add the following to your pytest.ini or tox.ini:

[pytest]
addopts = -p no:warnings

The result will be green without any indication of warnings. See documentation at https://docs.pytest.org/en/latest/warnings.html#disabling-warnings-summary.

This can be a valid use case for a test suite where you want clean output.

Be aware that always hiding all warnings may cause you to miss important warnings. If you want to hide only specific warnings, look at Cloc's answer.

I don't want to hide all warning, so I put this in pytest.ini

[pytest]
filterwarnings =
    ignore::DeprecationWarning