PEP 3132 -- Extended Iterable Unpacking inconsistent assignment of * variable

[cigani]

BPO	38516
Nosy	@stevendaprano, @cigani

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-10-18.12:11:14.454>
labels = ['3.7', 'library']
title = 'PEP 3132 -- Extended Iterable Unpacking inconsistent assignment of * variable'
updated_at = <Date 2019-10-18.12:41:04.898>
user = 'https://github.com/cigani'

bugs.python.org fields:

activity = <Date 2019-10-18.12:41:04.898>
actor = 'steven.daprano'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-10-18.12:11:14.454>
creator = 'mjaquier'
dependencies = []
files = []
hgrepos = []
issue_num = 38516
keywords = []
message_count = 2.0
messages = ['354881', '354886']
nosy_count = 2.0
nosy_names = ['steven.daprano', 'mjaquier']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue38516'
versions = ['Python 3.7']

[cigani]

x = [1,2,3]

Case (1)
*b, = x
*b == [1, 2, 3]

Case(2)
*b, _ = x 
b = [1,2]

Is it not more logical for this to give consistent values regardless.

i.e.,

*b, = [1,2,3] ; b == [1,2]

*b, _ = [1,3,2] ; b == [1,2] ; _ == [3]

[stevendaprano]

Why would they give the same result when the code is different?

#1 assign c, d, e and everything left over goes into b
*b, c, d, e, = [1, 2, 3, 4]

#2 assign c, d and everything left over goes into b
*b, c, d, = [1, 2, 3, 4]

#3 assign c and everything left over goes into b
*b, c, = [1, 2, 3, 4]

#4 assign nothing and everything left over goes into b
*b, = [1, 2, 3, 4]