Convert String to Code

How To Convert String To Runnable Code In Java

Janino is a popular choice for an on-demand-compiler. It's being used by many open source projects.

The usage is straight forward. The code

import org.codehaus.janino.ScriptEvaluator;

public class App {

    public static void main(String[] args) throws Exception {

        String x = "System.out.println(\"X\");"; //<-- dont forget the ; in the string here
        ScriptEvaluator se = new ScriptEvaluator();  
        se.cook(x);
        se.evaluate(new Object[0]);    
    }
}

prints x.

As others have already pointed out, loading code from the database and executing it might be a bit risky.

How can I convert string to source code in python?

You can use eval() function to evaluate Python source code.

Quoting the documentation:

eval(expression, globals=None, locals=None)

The arguments are a string and optional globals and locals. If provided, globals must be a dictionary. If provided, locals can be any mapping object.

What are the ways to convert a String into runnable code?

You can simple execute your code contained inside String using Quasiquotes(Experimental Module).

import scala.reflect.runtime.universe._
import scala.reflect.runtime.currentMirror
import scala.tools.reflect.ToolBox

// TO compile and run code we will use a ToolBox api.
val toolbox = currentMirror.mkToolBox()

// write your code starting with q  and put it inside double quotes.
// NOTE : you will have to use triple quotes if you have any double quotes usage in your code.
val code1 = q"""new String("hello")"""
//compile and run your code.
val result1 = toolbox.compile(code1)()

// another example
 val code2 = q"""
 case class A(name:String,age:Int){
    def f = (name,age)
 }
 val a = new A("Your Name",22)
 a.f
 """

 val result2 = toolbox.compile(code2)()

Output in REPL :

// Exiting paste mode, now interpreting.

import scala.reflect.runtime.universe._
import scala.reflect.runtime.currentMirror
import scala.tools.reflect.ToolBox
toolbox: scala.tools.reflect.ToolBox[reflect.runtime.universe.type] = scala.tools.reflect.ToolBoxFactory$ToolBoxImpl@69b34f89
code1: reflect.runtime.universe.Tree = new String("hello")
result1: Any = hello
code2: reflect.runtime.universe.Tree =
{
  case class A extends scala.Product with scala.Serializable {
    <caseaccessor> <paramaccessor> val name: String = _;
    <caseaccessor> <paramaccessor> val age: Int = _;
    def <init>(name: String, age: Int) = {
      super.<init>();
      ()
    };
    def f = scala.Tuple2(name, age)
  };
  val a = new A("Your Name", 22);
  a.f
}
result2: Any = (Your Name,22)

scala> 

To learn more about Quasiquotes :
http://docs.scala-lang.org/overviews/quasiquotes/setup.html

How to convert a string to python code in python?

Yes, eval() only evaluates expressions, not statements or suites (which comprise full Python programs).

You're looking for the exec() function.

exec("for i in range(100):\n\tprint(i)")

However, do remember you usually don't need eval() or exec(), and especially you'll never want to exec() or eval() user input.

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