Scala – exiting the repl console with a background process

For Python 2 give execfile a try. (See other answers for Python 3)

execfile('file.py')

Example usage:
Let's use "copy con" to quickly create a small script file...

C:\junk>copy con execfile_example.py
a = [9, 42, 888]
b = len(a)
^Z
        1 file(s) copied.

...and then let's load this script like so:

C:\junk>\python27\python
Python 2.7.1 (r271:86832, Nov 27 2010, 18:30:46) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> execfile('execfile_example.py')
>>> a
[9, 42, 888]
>>> b
3
>>>

It appears that you're trying to run & compile programs from within the Scala REPL (read-evaluate-print loop - a kind of Scala interpreter) and you cannot do that in the REPL. The REPL allows you to type in Scala statements and see them execute immediately. (If you're not sure how you entered the REPL, you probably just entered the command scala from the command line.) The REPL is useful for testing ideas, and for experimenting with Scala. For example:

C:\some\path> scala
Welcome to Scala version 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_91).
Type in expressions for evaluation. Or try :help.

scala> println ("Hello!")
Hello!

scala> val x = 10
x: Int = 10

scala> val y = x * 5
y: Int = 50

scala> sys.exit
C:\some\path>

However, the REPL isn't what you would use to compile & run Scala programs - you need to do that from the command line (or from a tool such as sbt). If you want to run your program directly from the command line, without using the REPL (that is, without being in Scala, as you put it) then you would need to do the following:

Firstly, compile your program using scalac:

C:\some\path> scalac Hello.scala

If that succeeds, you can then run the program with the scala command (which looks for a Hello.class file):

C:\some\path> scala Hello

(Here C:\some\path is the location of the files Hello.scala & Hello.class.)

Alternatively, as you have already discovered, you can run your Scala program as a script in the REPL. You can do this from the command line as follows (note the addition of the filetype .scala after Hello compared to the command above):

C:\some\path> scala Hello.scala

or from within the REPL:

scala> :load Hello.scala

Hope this helps!