I am learning python and I have as simple list as this
z = [1,2,3,4,5,6,7,8,9]
and I am just trying to unpack it, which throws me syntax error.
a,*b,c = z
>>> a,*b,c = z
File "<stdin>", line 1
a,*b,c = z
^
SyntaxError: invalid syntax
I tried changing the order of variable as well but same error. Any suggestion pls.
What your are trying to do does not work in Python2 because it does not have support for extended tuple unpacking - you pretty much have to use slicing.
>>> z = [1,2,3,4,5,6,7,8,9]
>>> a, b, c = z[0], z[1:-1], z[-1]
>>> a
1
>>> b
[2, 3, 4, 5, 6, 7, 8]
>>> c
9
Using Python3, you are allowed one wildcard:
Demo:
>>> z = [1,2,3,4,5,6,7,8,9]
>>> a, *b, c = z
>>> a
1
>>> b
[2, 3, 4, 5, 6, 7, 8]
>>> c
9
>>> *a, b, c = z
>>> a
[1, 2, 3, 4, 5, 6, 7]
>>> b
8
>>> c
9
>>> *a, *b, c = z
File "<stdin>", line 1
SyntaxError: two starred expressions in assignment
Python3.5 comes with some additional unpacking generalizations
>>> [1, 2, *[3, 4]]
[1, 2, 3, 4]
[*sublist for sublist in nested_list] in 3.5 to flatten a list of lists.
[*itertools.chain(*nested_list)] works. Not too bad; shortens if you import chain into global namespace directly.Here is a quote from PEP-3132
For example, if seq is a slicable sequence, all the following assignments are equivalent if seq has at least three elements:
a, b, c = seq[0], list(seq[1:-1]), seq[-1] a, *b, c = seq [a, *b, c] = seq
In Python2.7, only the first version is legal syntax.
Since you already know z is a list, you can just write
a, b, c = z[0], z[1:-1], z[-1]
This will work for Python2.7 and Python3.x
seq is a generator this won't work, better to do lst = list(seq) then slice lst.
*bis not a valid name for a variable*b? Were you trying to separate the first and last element from the middle of the list?