Puzzling difference between lists and tuples

[Ethan Furman]

On 9/17/20 8:24 AM, William Pearson wrote:

> I am puzzled by the reason for this difference between lists and tuples.
> 
> A list of with multiple strings can be reduced to a list with one string with the expected results:

> for n in ['first']:
>      print n

['first'] is a list.

> for n in ('first'):
>      print n

('first') is not a tuple.  The tuple operator is actually the comma:

 >>> not_a_tuple = ('first')
 >>> type(not_a_tuple)
<class 'str'>

 >>> is_a_tuple = 'first',
 >>> type(is_a_tuple)
<class 'tuple'>

I tend to use both as it makes it stand out a bit more:

 >>> still_a_tuple = ('first', )
 >>> type(still_a_tuple)
<class 'tuple'>

The only time the parentheses are required for tuple building is when 
they would otherwise not be interpreted that way:

some_func('first', 'second')   # some_func called with two str args

some_func(('first', 'second')) # some_func called with one tuple arg

--
~Ethan~