Interpreter base classes in Python

Python's interactive mode works on the principle of REPL (Read - Evaluate - Print - Loop). The code module in Python's standard library provides classes nd convenience functions to set up REPL environment from within Python script.

Following two classes are defined in code module:

InteractiveInterpreter: This class deals with parsing and interpreter state (the user’s namespace)

InteractiveConsole: Closely emulate the behavior of the interactive Python interpreter.

Two convenience functions in the module are:

interact(): Convenience function to run a read-eval-print loop.

compile_command(): This function is useful for programs that want to emulate Python’s interpreter main loop (the REPL).

Interactive Interpreter methods

runsource(): Compile and run some source in the interpreter.

runcode(): Execute a code object

Interactive Console methods:

Because the InteractiveConsole class is a subclass of InteractiveInterpreter, above methods are automatically available. Additionally following methods are defined.

interact(): Closely emulate the interactive Python console.

push(): Push a line of source text to the interpreter.

resetbuffer(): Remove any unhandled source text from the input buffer.

raw_input(prompt="")

Write a prompt and read a line by defaultfrom sys.stdin

Example

import code
x = 10
y = 20
def add(x,y):
   return x+y
print (add(x,y))
code.interact(local=locals())
print (x,y)
print (add(x,y))

In the above code, two vaiables are defined and passed to a function. The we invoke he interactive console. The argument local=locals() allows use of local namespace as the default within the interpreter loop.

If you assign different values to variables and exit the console by pressing ctrl+D, those values are now passed to the function

Output

addition= 30
Python 3.6.6 |Anaconda custom (64-bit)| (default, Oct 9 2018, 12:34:16)
[GCC 7.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> x=100
>>> y=200
>>>

now exiting InteractiveConsole...
100 200
addition = 300