The rampart-python module

Preface

License

The Python library is licensed under the PSF LICENSE.

The rampart-python module is released under the MIT license.

What does it do?

The rampart-python module includes functions which import Python modules and scripts, executes them and translates variables between Python and JavaScript.

How does it work?

The module and the embedded Python interpreter are used to load Python modules and scripts into the Python environment. Translation of variables between the two languages are handled automatically. As the Python Library does not function in parallel in multiple threads, if run in rampart.threads the module will run in multiple processes.

Loading the Javascript Module

Loading of the sql module from within Rampart JavaScript is a simple matter of using the require statement:

var python=require("rampart-python");
Return value:

An Object with the functions listed below.

Python Module Functions

python.import()

Import a python module.

Usage:

var python=require("rampart-python");

/* same as "import mymod" in Python */
var mymod=python.import("mymod");
Return Value:

An Object with callable properties corresponding to the functions of the imported module.

Example:

var python = require("rampart-python");

var pathlib = python.import('pathlib');

var pvar = pathlib.PosixPath('./');

python.importString()

Import a python module or script from a String.

Usage:

var python=require("rampart-python");

var mymod = python.importString(pyscript[, scriptName);

Where:

  • script is a String, the python source code

  • scriptName is a String, an optional name for this script for error reporting. Default is "module_from_string".

Return Value:

An Object with callable properties corresponding to the functions of the imported module.

Example:

var python=require("rampart-python");

var pyscript=`
def makedict(k,v):
    return {k:v}
`;

var mymod = python.importString(pyscript);

var pvar = mymod.makedict("mykey", ["val1", "val2"]);

python.importFile()

Import a python module or script from a file. Same as python.importString() except the source is loaded from the named file.

Usage:

var python=require("rampart-python");

var mymod = python.importFile(fileName);

Where:

  • fileName is a String, the path of the file to be imported.

Return Value:

An Object with callable properties corresponding to the functions of the imported module.

pvar.toString()

Return the string version of the python variable.

Example:

var python = require("rampart-python");

var pathlib = python.import('pathlib');

var pvar = pathlib.PosixPath('./');

rampart.utils.printf( "pathlib=%s\npvar=%s\npvar.resolve()=%s\n",
    pathlib.toString(), pvar.toString(), pvar.resolve().toString() );

/* output:
    pathlib=<module 'pathlib' from '/usr/local/rampart/modules/python3-lib/pathlib.py'>
    pvar=.
    pvar.resolve()=/path/to/my/current/directory
*/
Return Value:

An String.

pvar.toValue()

Translate the python variable referenced in pyvar to a JavaScript variable.

Example:

var python=require("rampart-python");
var printf = rampart.printf;

var mymod = python.importString("/path/to/myscript.py");

var pvar = mymod.makedict("mykey", ["val1", "val2"]);

printf( "mykey = %s\nmykey.toValue=%3J\n",
    pvar.mykey.toString(), pvar.mykey.toValue() );

/* output:
    mykey = ('val1', 'val2')
    mykey.toValue=[
       "val1",
       "val2"
    ]
*/

Handling Variables

From Javascript to Python

Variables passed to Python functions are automatically converted as follows:

JavaScript Type

Python Type

Number

Float

String

String

Array

Tuple

Object

Dictionary

Buffer

Bytes Object

Date

Datetime

Undefined

None

null

None

Where possible, translations can be specified by creating an Object with pyType and value properties set.

Example:

var python=require("rampart-python");
var printf = rampart.utils.printf;

var pyscript=`
def printvar(v):
    print( "%-30s %s" % (type(v), v))
`;

var mymod = python.importString(pyscript);

mymod.printvar({pyType: "date",    value: 946713599999});
mymod.printvar({pyType: "int",     value: "1234567800000000000000000000000000000000000000"});
mymod.printvar({pyType: "list",    value: ["a", "b", "c"]});
mymod.printvar({pyType: "tuple",   value: "d"});
mymod.printvar({pyType: "complex", value: [1,2]});
mymod.printvar({pyType: "dict",    value: "e"});

/* output:
    <class 'datetime.datetime'>    1999-12-31 23:59:59.999000
    <class 'int'>                  1234567800000000000000000000000000000000000000
    <class 'list'>                 ['a', 'b', 'c']
    <class 'tuple'>                ('d',)
    <class 'complex'>              (1+2j)
    <class 'dict'>                 {'0': 'e'}
*/

From Python to JavaScript

Translation of return values from Python are automatic when using .toValue(). For types which cannot be translated, a string representation (same as .toString()) will be returned instead.

Example:

var python=require("rampart-python");
var printf = rampart.utils.printf;

var pyscript=`
def retvar(v):
    return v
`;

var mymod = python.importString(pyscript);

var ret;

ret=mymod.retvar({pyType:"date", value: 946713599999});
printf("%J\n", ret.toValue());

ret=mymod.retvar({pyType: "int",     value: "1234567800000000000000000000000000000000000000"});
printf("%J\n", ret.toValue());

ret=mymod.retvar({pyType: "list",    value: ["a", "b", "c"]});
printf("%J\n", ret.toValue());

ret=mymod.retvar({pyType: "tuple",   value: "d"});
printf("%J\n", ret.toValue());

ret=mymod.retvar({pyType: "complex", value: [1,2]});
printf("%J\n", ret.toValue());

ret=mymod.retvar({pyType: "dict",    value: "e"});
printf("%J\n", ret.toValue());

ret=mymod.retvar(mymod);
printf("%J\n", ret.toValue());

/* output:
    "1999-12-31T23:59:59.999Z"
    1.2345678e+45
    ["a","b","c"]
    ["d"]
    [1,2]
    {"0":"e"}
    <module 'module_from_string' from '/home/user/src/mytest.js'>
*/

Python to Python

Variables returned from a Python function can be used as parameters to other Python functions. No translation will be performed.

Example:

 var python=require("rampart-python");
 var printf = rampart.utils.printf;

 var pyscript=`
 def retvar(v):
     return v

 def add(a,b):
     return a+b;
 `;

 var a = mymod.retvar({pyType: "complex", value: [1,2]});
 var b = mymod.retvar({pyType: "complex", value: [3,4]});
 var ret = mymod.add(a, b);
 printf("%J\n", ret.toValue());

 /* output:
     [3,4]

    note that var a and b hold the Python variables and are
    not translated when mymod.add(a,b) is called.
*/

Python Named Arguments

Named arguments to Python functions may be use as shown in the following example:

var python=require("rampart-python");
var printf = rampart.utils.printf;

var pyscript=`
def retvar(v):
    return v

def add(a,b):
    return a+b;
`;

var comp1 = mymod.retvar({pyType: "complex", value: [1,2]});
var comp2 = mymod.retvar({pyType: "complex", value: [3,4]});

var myNamedArgs = { pyArgs: {a:comp1, b:comp2} };

var ret = mymod.add( myNamedArgs );
printf("%J\n", ret.toValue());

/*
   calling in JavaScript:
       mymod.add( {pyArgs: {a:comp1, b:comp2} } );
   is equivalent to calling with named arguments in python:
       add(a=comp1, b=comp2);
*/

Example Use Importing Data

var python = require('rampart-python');
var Sql = require('rampart-sql');
var printf = rampart.utils.printf;

/* create the rampart sql db*/
var sql = new Sql.init("./pytest-sql", true);

/* the sqlite db */
var dbfile="./test.db";

/* use python to create and connect to sqlite db */
var pysql = python.import('sqlite3');
var connection = pysql.connect(dbfile);
var cursor = connection.cursor();

/* create a test table */
cursor.execute("create table IF NOT EXISTS test(i int, i2 int);");

/* insert some test data into the db */
for (var i=0; i<100; i+=2) {
    cursor.execute("insert into test values(?,?)", [i,   i+1]);
}

/* print out what we have */
cursor.execute("select * from test");
res = cursor.fetchall().toValue();
printf("Dump of sqlite table:\n%J\n", res);


/* create rampart sql table and copy data from sqlite */
sql.exec("create table test (i int, i2 int);");
for (i=0;i<res.length;i++) {
    sql.exec("insert into test values(?,?);", res[i]);
}

var res2 = sql.exec("select * from test", {returnType:"array", maxRows:-1});
printf("Dump of rampart sql table:\n%J\n", res2.rows);

/* output:
    Dump of sqlite table:
    [[0,1],[2,3],[4,5],[6,7],[8,9],[10,11],[12,13],[14,15],[16,17],[18,19],[20,21],[22,23],[24,25],
      [26,27],[28,29],[30,31],[32,33],[34,35],[36,37],[38,39],[40,41],[42,43],[44,45],[46,47],[48,49],
      [50,51],[52,53],[54,55],[56,57],[58,59],[60,61],[62,63],[64,65],[66,67],[68,69],[70,71],[72,73],
      [74,75],[76,77],[78,79],[80,81],[82,83],[84,85],[86,87],[88,89],[90,91],[92,93],[94,95],[96,97],[98,99]]
    Dump of rampart sql table:
    [[0,1],[2,3],[4,5],[6,7],[8,9],[10,11],[12,13],[14,15],[16,17],[18,19],[20,21],[22,23],[24,25],
      [26,27],[28,29],[30,31],[32,33],[34,35],[36,37],[38,39],[40,41],[42,43],[44,45],[46,47],[48,49],
      [50,51],[52,53],[54,55],[56,57],[58,59],[60,61],[62,63],[64,65],[66,67],[68,69],[70,71],[72,73],
      [74,75],[76,77],[78,79],[80,81],[82,83],[84,85],[86,87],[88,89],[90,91],[92,93],[94,95],[96,97],[98,99]]

*/