added some possible sources

README.md

 # python-c-interface
 
-Repo for interfacing python with c. Main goal is to be able to compile a function and give the pointer to that function to a c program.
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+Repo for interfacing python with c. Main goal is to be able to compile a function and give the pointer to that function to a c program.
+
+# Leads:
+# https://stackoverflow.com/questions/17980167/writing-python-ctypes-for-function-pointer-callback-function-in-c
+# https://wiki.python.org/moin/IntegratingPythonWithOtherLanguages
+# https://cffi.readthedocs.io/en/release-1.4/using.html?highlight=re
+# http://www.swig.org/Doc1.3/SWIG.html#SWIG_nn30
+# https://stackoverflow.com/questions/51273804/returning-a-function-python-c-api
+# https://docs.scipy.org/doc/numpy/reference/c-api.types-and-structures.html#c.PyArray_ArrFuncs.fillwithscalar
+# https://stackoverflow.com/questions/43162622/python-passing-pointers-between-c-and-python-with-ctypes
+# https://stackoverflow.com/questions/4213095/python-and-ctypes-how-to-correctly-pass-pointer-to-pointer-into-dll
+
+# https://stackoverflow.com/questions/41954269/create-c-function-pointers-structure-in-python
+# https://stackabuse.com/enhancing-python-with-custom-c-extensions/ Read
+# https://stackoverflow.com/questions/49941617/runtime-generation-and-compilation-of-cython-functions
+# https://realpython.com/cpython-source-code-guide/
+# https://docs.python.org/3.6/c-api/index.html
+# https://stackoverflow.com/questions/6626167/build-a-pyobject-from-a-c-function
+# https://docs.python.org/3.6/extending/newtypes_tutorial.html?highlight=pointer
+# https://realpython.com/cpython-source-code-guide/
+# https://diseraluca.github.io/blog/2019/03/21/wetting-feet-with-python-c-api
+# https://docs.python.org/3/c-api/function.html
+
+# http://koichitamura.blogspot.com/2008/06/this-is-small-python-capi-tutorial.html
+# https://cython.readthedocs.io/en/latest/src/userguide/external_C_code.html#including-verbatim-c-code probably works too!
+# https://www.oreilly.com/library/view/python-cookbook/0596001673/ch16s07.html
+# https://stackoverflow.com/questions/53215786/when-writing-a-python-extension-in-c-how-does-one-pass-a-python-function-in-to
+# https://pythonextensionpatterns.readthedocs.io/en/latest/refcount.html
+# https://bitbucket.org/cffi/cffi/issues/265/cffi-doesnt-allow-creating-pointers-to
+# https://stackoverflow.com/questions/40166645/a-c-pointer-passed-between-c-and-python-using-capsule-is-empty
+# https://www.youtube.com/watch?v=2B0CMF3cYPA
+# https://stackoverflow.com/questions/16993927/using-cython-to-link-python-to-a-shared-library