python examples added

python/README.md

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+# Examples of embedded GF grammars in Python
+
+The grammars use the Python binding available in
+
+https://github.com/GrammaticalFramework/gf-core
+
+see
+
+`src/runtime/python/` 
+
+for installing the Python module `pgf`, and
+
+`src/runtime/c/`
+
+for the C runtime library that the bindings are based on.
+You don't need Haskell to build these.
+
+A general tutorial on the Python bindings can be found in
+
+http://www.grammaticalframework.org/doc/runtime-api.html#python
+
+A guide to GF for Python programmers can be found in
+
+https://daherb.github.io/GF-for-Python-programmers/
+
+
+## Translator
+
+A minimal translator can be found in
+
+[`minitranslator.py`](./minitranslator.py)
+
+This program reads one line of input and translates it from English to Swedish by using `MiniGrammar.pgf`. Example:
+```
+$ echo "the cat is black" | python3 minitranslator.py
+katten är svart
+```
+A more general version is in
+
+[`translator.py`](./translator.py)
+
+This program reads input line by line, tokenizes it (by a simple tokenizer), and uses an arbitrary pgf and language codes. Example:
+```
+$ cat findrawscript.txt | python3 translator.py Draw Fin Eng
+# translating with Draw.pgf from DrawFin to DrawEng
+draw a small red circle
+draw a big yellow square
+move the small red circle
+remove it
+```
+
+
+## Drawing figures
+
+A minimal drawing program with natural language input can found in
+
+[`minidraw.py`](./minidraw.py)
+
+This program reads one line of input in English and converts it to an action of drawing a circle or a square. Example:
+```
+$ python3 minidraw.py
+draw a circle
+```
+The result is [this window](./dump-minidraw.png).
+The program uses the simple graphics library from
+
+https://mcsp.wartburg.edu/zelle/python/graphics.py
+
+We also presuppose the grammar to be compiled with
+`
+make draw
+`
+A more complete version (using the same grammar) is in
+
+[`draw.py`](./draw.py)
+
+This program opens a session where it reads input line by line, in a language specified by a language code. Example:
+```
+$ python3 draw.py Eng
+draw a small red circle
+draw a blue square
+move it        
+move the small red circle
+```
+The result is [this window](./dump-draw.png).
+
+The grammar, [`Draw.gf`](./Draw.gf), illustrates a few things...
+
+
+## Answering queries
+
+A minimal query answering program with natural language input can found in
+
+[`miniquery.py`](./miniquery.py)
+
+This program reads one line of input in English and executes a query, which is either asking if a number is prime, or calculating a sum. Examples:
+```
+$ echo "is 143 prime" | python3 miniquery.py 
+False
+$ echo "1 + 2 + 3" | python3 miniquery.py 
+6
+```
+We presuppose the grammar to be compiled with
+`
+make query
+`
+A more complete version (using the same grammar) is in
+
+[`query.py`](./query.py)
+
+This program uses a large grammar with more predicates, operations, and logical forms such as quantifiers. It still reads just one line of input, but allows the language to be specified by a language code. Example:
+```
+$ echo "what is the factorial of 12" | python3 query.py Eng 
+479001600
+$ echo "prime numbers between 200 and 300" | python3 query.py Eng 
+[211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293]
+WARNING: ambiguous
+$ echo "are all prime numbers odd" | python3 query.py Eng 
+False
+```
+The grammar, [`Query.gf`](./Query.gf), illustrates a few things...
+