Is Python a functional programming language?

[Nobody]

On Tue, 11 May 2010 18:31:03 -0700, Paul Rubin wrote:

>>> is called an "equation" rather than an "assignment".  It declares "x is
>>> equal to 3", rather than directing x to be set to 3.  If someplace else
>>> in the program you say "x = 4", that is an error, normally caught by
>>> the compiler, since x cannot be equal to both 3 and 4.
>>
>> In both ML and Haskell, bindings are explicitly scoped, i.e.
>> 	let x = 3 in ...	(Haskell)
> 
> I'm not talking about nested bindings.  I'm talking about two different
> bindings of the same symbol in the same scope:
> 
>     $ cat meow.hs
>     x = 3
>     x = 4
>     $ ghc meow.hs
> 
>     meow.hs:2:0:
>         Multiple declarations of `Main.x'
>         Declared at: meow.hs:1:0
>                      meow.hs:2:0

It may be worth noting the interactive behaviour:

	$ ghci
	GHCi, version 6.8.2: http://www.haskell.org/ghc/  :? for help
	Loading package base ... linking ... done.
	Prelude> let x = 7
	Prelude> let f y = x + y
	Prelude> f 3
	10
	Prelude> let x = 5
	Prelude> f 3
	10

The main point is that variables aren't mutable state.

An important secondary point is that, unlike Python, free (global)
variables in a function body are substituted when the function is defined,
not when it's called.