A Lisp written in Python. It is designed to have access to variables created in the Python script from which it is run. While the interpreter does have its own symbol table (so defining a name var will not overwrite the variable var in the Python script), if a symbol isn't found in the table, it will be looked for in the global context of the Python script from which the interpreter was called. This is mostly useful for creating functions in Python and then calling them in PyParens.

It also has a lot of minor problems, like:

• Comments are not yet implemented
• The lexical analyzer is very slow
• Only double quoted strings are allowed
• It is a toy and is not tested
• I'm not done building the default environment

Some examples:

pl> (define a 3)
R: 3
pl> (print (+ a 3) )
6
NR~

What is happening here is I am setting a variable (which is now accessible in Python, too, through the env table) called a. I then print (using the standard Python print function) the result of a + 3. Of course, print returns nothing, so the interpreter informs me of this with NR~.

pl> (define a 1)
R: 1
pl> (if (= a 1) (print "Yes") (print "No"))
Yes
NR~

Here, I'm using an if statement. It is a special form. I plan to implement it as a Python function and put it in the symbol table eventually.

Other special forms include import and .. They go well together:

pl> (. (import math) pi)
R: 3.141592653589793