Why tuples need brackets to list comprehension

Question

It is well known that tuples are not defined by brackets, but by commas. Quote from the documentation :

A tuple consists of several values ​​separated by commas

Thus:

myVar1 = 'a', 'b', 'c'
type(myVar1)
# Result:
<type 'tuple'>

Another striking example:

myVar2 = ('a')
type(myVar2)
# Result:
<type 'str'>  

myVar3 = ('a',)
type(myVar3)
# Result:
<type 'tuple'>

Even a singleton tuple needs a comma, and parentheses are always used to avoid confusion. My question is: Why can't we omit the parentheses of arrays in list comprehension? For example:

myList1 = ['a', 'b']
myList2 = ['c', 'd']

print([(v1,v2) for v1 in myList1 for v2 in myList2])
# Works, result:
[('a', 'c'), ('a', 'd'), ('b', 'c'), ('b', 'd')]

print([v1,v2 for v1 in myList1 for v2 in myList2])
# Does not work, result:
SyntaxError: invalid syntax

Is it not understanding the second list of just syntactic sugar for the next cycle that works?

myTuples = []
for v1 in myList1:
    for v2 in myList2:
        myTuple = v1,v2
        myTuples.append(myTuple)
print myTuples
# Result:
[('a', 'c'), ('a', 'd'), ('b', 'c'), ('b', 'd')]

Answer 1

Python LL (1), , .

[(v1, v2) for v1 in myList1 for v2 in myList2]

- .

[ # An opening bracket; must be some kind of list
[( # Okay, so a list containing some value in parentheses
[(v1
[(v1,
[(v1, v2
[(v1, v2)
[(v1, v2) for # Alright, list comprehension

, , .

[v1, v2 for v1 in myList1 for v2 in myList2]

[ # List-ish thing
[v1 # List containing a value; alright
[v1, # List containing at least two values
[v1, v2 # Here the second value
[v1, v2 for # Wait, what?

, , , , LL (1) . , .

Answer 2

", " , .

/set/tuple , for.

:

$ python3.6 test.py
  File "test.py", line 1
    [a, b for a, b in c]
            ^
SyntaxError: invalid syntax

:

$ python3.6 -m tokenize test.py
0,0-0,0:            ENCODING       'utf-8'        
1,0-1,1:            OP             '['            
1,1-1,2:            NAME           'a'            
1,2-1,3:            OP             ','            
1,4-1,5:            NAME           'b'            
1,6-1,9:            NAME           'for'          
1,10-1,11:          NAME           'a'            
1,11-1,12:          OP             ','            
1,13-1,14:          NAME           'b'            
1,15-1,17:          NAME           'in'           
1,18-1,19:          NAME           'c'            
1,19-1,20:          OP             ']'            
1,20-1,21:          NEWLINE        '\n'           
2,0-2,0:            ENDMARKER      ''