Fast way to make list with same entry multiple times in Python?

Question

Is there an elegant way in python to make a list of duplicate things?

For example, I want to make a list of 7 lefts, like so:

x = ['left', 'left', 'left', 'left', 'left', 'left', 'left']

other than doing something like:

x = []
for y in xrange(7):
    x.append('left')

is there a way to efficiently make a list of 7 lefts? I had hoped for something like: x = ['left' * 7], but of course that gives me ['leftleftleftleftleftleftleft'].

Thanks a lot, Alex

Yeah, looks like that's pretty much the same question, sorry. — Alex S, Dec 22 '13 at 22:34

score 9 · Accepted Answer · answered Dec 22 '13 at 22:01

If you want (or simply are okay with) a list of references to the same object, list multiplication is what you want:

x = ['left'] * 7

If you need separate objects, e.g. if you're initializing a list of lists, you want a list comprehension:

x = [[] for _ in xrange(7)]

score 3 · Answer 2 · answered Dec 22 '13 at 22:00

3

What about something like x = ['left'] * 7?

answered Dec 22 '13 at 22:00

Paulo Bu

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score 3 · Answer 3 · answered Dec 22 '13 at 22:30

3

>>> list = ['left' for x in range(7)]
>>> list
>>>['left', 'left', 'left', 'left', 'left', 'left', 'left']

answered Dec 22 '13 at 22:30

Xar

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score 1 · Answer 4 · answered Dec 22 '13 at 22:00

1

['left'] * 7

or

[ 'left' for _dummy in range(7) ]

answered Dec 22 '13 at 22:00

shx2

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score 0 · Answer 5 · answered Dec 22 '13 at 22:01

0

Lost comprehension

['Left' for _ in range(7)]

answered Dec 22 '13 at 22:01

migajek

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Fast way to make list with same entry multiple times in Python?

5 Answers5