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+These directories specify the Python (and system) dependencies for the LMS and Studio.
+
+- ``edx`` contains the normal Python requirements files
+- ``edx-sandbox`` contains the requirements files for Codejail
+- ``constraints.txt`` is shared between the two
+
+(In a normal `OEP-18`_-compliant repository, the ``*.in`` and ``*.txt`` files would be
+directly in the requirements directory.)
+
+.. _OEP-18: https://github.com/edx/open-edx-proposals/blob/master/oeps/oep-0018-bp-python-dependencies.rst