I am amazed that people say Lisp is about macros. I think it's about being homoiconic. You can make some ugly form of macros in ANY language. Homoiconic-ness is what makes you want to make macros with Lisp. But it is much more than just about macros. Language REBOL is for example fully homoiconic.

  >> a: [ 300 3 ]
  >> insert a 'add
  >> probe a
  [ add 1 2 ]
  >> print first a
  add
  >> do first a 100 1
  == 101
  >> do a
  == 303
  >> f: func [] a
  >> f
  == 3
  >> change second :f 'subtract
  >> f
  == 297

all code is data (blocks of words and values).

From * Io * example below I would say it's a little different. It's more like it has a runtime api to change/generate it's runtime. I think SmallTalk has something similar to this.

* Factor * has compile time macros. At runtime it has quotations, which are blocks of code (separate from it's other data strucures I think, but don't shoot me if I'm wrong) that can be modified and executed by your code with few specific words like curry and compose. This means you have a little less freedom than in rebol where block of code is in no way different than a block of data. What is awesome about factor is that it also compiles quotations at runtime.

Otherwise Factor is very very cool, and I envy some runtime features of Io a lot.

And Python has as little to do with lisp as Visual Basic. Python is the world's best dynamic Imperative lang IMHO :)