Can tuples be replaced with lists all the time?

Sat Feb 22 23:49:19 EST 2014

Sam <lightaiyee at gmail.com> writes:
> My understanding of Python tuples is that they are like immutable
> lists.

That's a common expression, but I think it's not a helpful way to think
of them.
Rather, the different sequence types have different semantic purposes:
* For representing a sequence where each item means exactly the same no
 matter which position it's in (a “homogeneous sequence”), use a list.
* For representing a sequence where the meaning of each item is strongly
 dependent on its position in the sequence (a “heterogeneous
 sequence”), use a tuple.
See <URL:http://docs.python.org/3/library/stdtypes.html> for the
official Python description of the type differences.
> If this is the cause, why can't we replace tuples with lists all the
> time (just don't reassign the lists)? Correct me if I am wrong.

Because we need to represent different semantic concepts in our code,
and have each type support the semantics with different operations.
-- 
 \ “I went camping and borrowed a circus tent by mistake. I didn't |
 `\ notice until I got it set up. People complained because they |
_o__) couldn't see the lake.” —Steven Wright |
Ben Finney