Add hello-covenantsql demo

Author: ggicci

.gitignore

@@ -102,3 +102,6 @@ venv.bak/
 
 # mypy
 .mypy_cache/
+
+# Project specified
+.vscode/

Pipfile

@@ -0,0 +1,14 @@
+[[source]]
+url = "https://pypi.org/simple"
+verify_ssl = true
+name = "pypi"
+
+[packages]
+pycovenantsql = "*"
+
+[dev-packages]
+pylint = "*"
+yapf = "*"
+
+[requires]
+python_version = "3.6"

Pipfile.lock

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+# CovenantSQL Python Demos
+
+This project contains several domos for demonstrating how to utilize CovenantSQL's python driver.
+
+## 1. Setup
+
+```bash
+git clone https://github.com/CovenantSQL/python-demos.git
+cd python-demos
+pipenv install
+```
+
+## 2. Run a Demo
+
+```bash
+pipenv shell
+cd hello-covenantsql
+chmod u+x main.py
+./main.py
+```

README.md

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+# hello-covenantsql
+
+CovenantSQL's "hello world" demo.
+
+## Usage
+
+```bash
+./main.py
+```
+
+Expected output:
+
+```
+$ ./main.py
+create table
+insert sample data
+affected rows: 1, lastrowid: 1
+select data from the table
+(1, '2018-11-06T18:21:23Z', 'Apple', 'appleisdelicious')
+
+$ ./main.py
+create table
+insert sample data
+affected rows: 1, lastrowid: 2
+select data from the table
+(1, '2018-11-06T18:21:23Z', 'Apple', 'appleisdelicious')
+(2, '2018-11-06T18:21:35Z', 'Apple', 'appleisdelicious')
+```
+
+**NB:** you can tweak database configurations through environment variables:
+
+```bash
+COVENANTSQL_HOST=192.168.2.xxx COVENANTSQL_PORT=12345 ./main.py
+```
+
+Available environment variables are:
+
+- **COVENANTSQL_HOST:** domain of the CovenantSQL adapter service;
+- **COVENANTSQL_PORT:** port of the CovenantSQL adapter service;
+- **COVENANTSQL_PRIVATE_KEY:** path of the private key file;
+- **COVENANTSQL_PROXY_PEM:** path of the proxy pem file;
+- **COVENANTSQL_DATABASE:** database name (hash).

hello-covenantsql/README.md

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+#!/usr/bin/env python3
+"""
+PyCovenantSQL driver demo: hello-covenantsql
+"""
+
+import os
+import pycovenantsql
+
+DB_CONFIG = {
+    'host':
+    os.getenv('COVENANTSQL_HOST', '127.0.0.1'),
+    'port':
+    int(os.getenv('COVENANTSQL_PORT', '11105')),
+    'key':
+    os.getenv(
+        'COVENANTSQL_PRIVATE_KEY',
+        './test/service/node_c/admin.test.covenantsql.io-key.pem',
+    ),
+    'https_pem':
+    os.getenv(
+        'COVENANTSQL_PROXY_PEM',
+        './test/service/node_c/admin.test.covenantsql.io.pem',
+    ),
+    'database':
+    os.getenv(
+        'COVENANTSQL_DATABASE',
+        '057e55460f501ad071383c95f691293f2f0a7895988e22593669ceeb52a6452a',
+    ),
+}
+
+
+def main():
+    """
+    Main program
+    """
+
+    conn = pycovenantsql.connect(**DB_CONFIG)
+    with conn.cursor() as cursor:
+        # Create a new table
+        sql_create_table = """
+        CREATE TABLE IF NOT EXISTS `users` (
+            `id` INTEGER PRIMARY KEY AUTOINCREMENT,
+            `created_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+            `email` VARCHAR(255) NOT NULL,
+            `password` VARCHAR(255) NOT NULL
+        );
+        """
+        print('create table')
+        cursor.execute(sql_create_table)
+
+        # Insert some data
+        print('insert sample data')
+        sql_insert_data = """INSERT INTO `users` (`email`, `password`) VALUES (%s, %s)"""
+        affected_rows = cursor.execute(
+            sql_insert_data,
+            ('Apple', 'appleisdelicious'),
+        )
+        print('affected rows: %d, lastrowid: %d' % (
+            affected_rows,
+            cursor.lastrowid,
+        ))
+
+        # Query data
+        print('select data from the table')
+        sql_select_data = """SELECT * FROM `users`"""
+        cursor.execute(sql_select_data)
+        for row in cursor:
+            print(row)
+        conn.close()
+
+
+if __name__ == '__main__':
+    main()