Message 159899 - Python tracker

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In-reply-to
Author	darrell
Recipients	darrell
Date	2012年05月04日.04:13:41
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<1336104822.52.0.958479666589.issue14719@psf.upfronthosting.co.za>

Content
N = 5 board_1 = [[0 for _ in range(N)] for __ in range(N)] is not the same as: board_2= [[0]N]N One makes a proper list of lists (the first), the second makes a new kind of animal were board_2[1][1] = 99 changes a whole column. Oddly, testing board_1 == board_2 is True! I'm teaching Python to non-majors, and this is a tough one to explain.

Content

N = 5
board_1 = [[0 for _ in range(N)] for __ in range(N)]
is not the same as:
board_2= [[0]*N]*N
One makes a proper list of lists (the first), the second makes a new kind of animal were board_2[1][1] = 99 changes a whole column.
Oddly, testing board_1 == board_2 is True!
I'm teaching Python to non-majors, and this is a tough one to explain.

History
Date	User	Action	Args
2012年05月04日 04:13:42	darrell	set	recipients: + darrell
2012年05月04日 04:13:42	darrell	set	messageid: <1336104822.52.0.958479666589.issue14719@psf.upfronthosting.co.za>
2012年05月04日 04:13:41	darrell	link	issue14719 messages
2012年05月04日 04:13:41	darrell	create

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