beginning chapter on python

README.md

@@ -318,6 +318,7 @@ In this section, we present miscellaneous material.
 | 3 | [Variadic Functions](./more/varargs/README.md) | [Link](./more/varargs/README.pdf) |
 | 4 | [Under the hood: System Calls](./more/system_calls/README.md) | [Link](./more/system_calls/README.pdf) |
 | 5 | [Determining string literal lengths for C functions](./more/strlen_for_c/README.md) | [Link](./more/strlen_for_c/README.pdf) |
+| 6 | [Calling Assembly Language From Python](./python/) | [Link](./python/README.pdf) |
 
 ## Macro Suite
 

python/README.md

@@ -0,0 +1,75 @@
+# Python / Assembly Language
+
+It is possible to call your assembly language code from Python. In fact,
+it can be insanely easy. It can also be difficult. What differentiates
+the two are the arguments you need to pass.
+
+Python stores data ina very different way than C and therefore assembly
+language. All Python data types are objects, which for sets and dicts
+can make things difficult and outside the scope of this book.
+
+If you want to explore the subject deeply, we suggest
+[this link](https://realpython.com/python-bindings-overview)
+
+## Simple EXample
+
+Take this trivial C function:
+
+```c
+int square(int x) {
+    return x * x;
+}
+```
+
+It could be written in this way using our Apple / Linux convergence
+macros:
+
+```text
+#include "apple-linux-convergence.S"
+
+/*
+    gcc -fPIC -shared -o my_square.so function.S 
+*/
+        .p2align    2
+        .text
+        GLABEL      square
+
+#if defined(__APPLE__)
+_square:
+#else
+square:
+#endif
+
+        mul     x0, x0, x0
+        ret
+
+        .end
+```
+
+This function is a leaf and requires no interaction with the stack.
+
+Notice there is no `main()`.
+
+Using the following command line, turn your assembly language module
+into a "shared object" or .so file:
+
+```text
+gcc -fPIC -shared -o my_square.so function.S
+```
+
+`-fPIC` means generate position independent code. This allows the library
+to be relocated wherever the program loading the library wants it.
+
+Then, in Python:
+
+```python
+from ctypes import *
+
+so_file  = "./my_square.so"
+my_funcs = CDLL(so_file)
+print(my_funcs.square(10))
+```
+
+It just works.
+
+## More to Come Here

python/test.py

@@ -1,4 +1,5 @@
 from ctypes import *
+
 so_file  = "./my_square.so"
 my_funcs = CDLL(so_file)
 print(my_funcs.square(10))