For loop with 2 elements. No zip

[buran]

So, in this way I iterate on only one tuple.

yes, like @bowlofred already mentioned, brackets are not mandatory. item is still a tuple. But here it is also in the docs:

Tuples may be constructed in a number of ways:

• Using a pair of parentheses to denote the empty tuple: ()
  
• Using a trailing comma for a singleton tuple: a, or (a,)
  
• Separating items with commas: a, b, c or (a, b, c)
  
• Using the tuple() built-in: tuple() or tuple(iterable)
  

The constructor builds a tuple whose items are the same and in the same order as iterable’s items. iterable may be either a sequence, a container that supports iteration, or an iterator object. If iterable is already a tuple, it is returned unchanged. For example, tuple('abc') returns ('a', 'b', 'c') and tuple( [1, 2, 3] ) returns (1, 2, 3). If no argument is given, the constructor creates a new empty tuple, ().

Note that it is actually the comma which makes a tuple, not the parentheses. The parentheses are optional, except in the empty tuple case, or when they are needed to avoid syntactic ambiguity. For example, f(a, b, c) is a function call with three arguments, while f((a, b, c)) is a function call with a 3-tuple as the sole argument.