Python 3.4 bugs

[vasyayugov]

BPO	24463
Nosy	@smontanaro, @ronaldoussoren, @ned-deily

^{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 = <Date 2015-06-18.11:29:20.243>
created_at = <Date 2015-06-18.11:01:13.014>
labels = ['OS-mac', 'type-bug', 'invalid']
title = 'Python 3.4 bugs'
updated_at = <Date 2015-06-18.11:29:20.221>
user = 'https://bugs.python.org/vasyayugov'

bugs.python.org fields:

activity = <Date 2015-06-18.11:29:20.221>
actor = 'skip.montanaro'
assignee = 'none'
closed = True
closed_date = <Date 2015-06-18.11:29:20.243>
closer = 'skip.montanaro'
components = ['macOS']
creation = <Date 2015-06-18.11:01:13.014>
creator = 'vasya yugov'
dependencies = []
files = []
hgrepos = []
issue_num = 24463
keywords = []
message_count = 2.0
messages = ['245460', '245462']
nosy_count = 4.0
nosy_names = ['skip.montanaro', 'ronaldoussoren', 'ned.deily', 'vasya yugov']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue24463'
versions = ['Python 3.4']

[vasyayugov]

This code:

w = [[0] * 2] * 2
w[1][1] = 1
print(w)

prints
[[0, 1], [0, 1]]
Is it a bug?

[smontanaro]

Not a bug. The two elements of w are references to the same list:

>>> w = [[0] * 2] * 2
>>> w
[[0, 0], [0, 0]]
>>> [id(elt) for elt in w]
[21743952, 21743952]