New submission from Jaap Woldringh <jjhwoldri...@ziggo.nl>:
Python used:
Python 3.6.9 (default, Nov 7 2019, 10:44:02)
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
In Ubuntu 18.04.3
But in any other version of Python3, and Python2, that I tried, the behaviour
of a (square) matrix depends on how it is created; as I can demonstrate in a
test program matrix_experiment.py that is attached to this report.
1. it behaves as expected when created by entering all it’s elements like so:
A = [[ 1,2,3],[1,2,3],[1,2,3]]
2. If it is created by appending predefined rows, it behaves as if all rows are
the same as the last row:
row = [1,2,3]
B=[]
for i in range(3):
B.appends(row)
The result matrix is the same as A: [[1, 2, 3], [1, 2, 3], [1, 2, 3]]
Both results are equal:
print(A==B) gives True.
But when using B the result is disastrous as the attached matrix_experiment.py
program shows.
I consider this a very serious bug, and first filed it at Ubuntu’s Launchpad,
but I don't find it there.
So now I file this again, at Python.org itself, using my new account.
----------
components: Tests
files: matrix_experiment.py
messages: 360182
nosy: jjhwoldringh
priority: normal
severity: normal
status: open
title: A matrix (list of lists) behaves differently, depending how it is created
type: behavior
versions: Python 3.6
Added file: https://bugs.python.org/file48849/matrix_experiment.py
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue39368>
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