Python self-evaluating strings

[Arnaud Delobelle]

Hi all,

An earlier post today got me thinking about "quines" (programs that  
output themselves) in Python.  I tried to find some on the web but  
didn't find many ([1]).  In particular I didn't find any that  
corresponded to my instinctive (LISP-induced, probably) criterion:

def self_evaluating(s):
	"Return True if string s evaluates to itself"
	return s == eval(s)

Here is the result of my efforts so far:

1. Starting from the classic idea (lambda x:x%x)('lambda x:x%x') I got  
the following
v=(lambda x:x%('"''""'+x+'"''""'))("""(lambda x:x%%('"''""'+x+'"''""')) 
(%s)""")

2. (Given that if s is a nonempty string, s*2 is a longer string).   
Starting from the idea "%s %s" % (("%s %s",)*2) I got the following
u="\"%s\" %% ((r\"%s\",)*2)" % ((r"\"%s\" %% ((r\"%s\",)*2)",)*2)

Most of my problems in creating these 2 was with finding a suitable  
way of quoting strings that propagates well. Both u and v are one- 
liners.  I'm hoping for no funky line wrapping here.

Note: I'm not quoting the string as it makes no difference since they  
evaluate to themselves:)

I'd like to know if anyone on the list has indulged in this time- 
bending/mind-wasting activity before.  If so, it would be nice to  
create a list of such expressions.

Quining's-better-than-ironing'ly yours

-- 
Arnaud

[1] http://www.nyx.net/~gthompso/self_pyth.txt