Python - Creating a Nested List with value using One line code [duplicate]

Question

I want to create a nested list in one line. List will be:

a = [["-","-",..."-"],["-","-",..."-"],...["-","-",..."-"]]

Each inner list should have 10 "-"s and the nested list should have 10 lists in it.

I've tried that one but it does not work as i wanted:

a = ["-","-","-","-","-","-","-","-","-","-"]*10

print(a)

Output was:

['-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-']

ScottC · Accepted Answer · 2022-12-24 09:00:09Z

1

The following code should produce a nested list as expected:

Code:

a = [["-"]*10]*10
print(a)

Output:

[['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-']]

answered Dec 24, 2022 at 9:00

ScottC

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Comments

Yash Mehta · Accepted Answer · 2022-12-24 09:07:00Z

#Not in refrenced form
a = [['-' for col in range(10)] for row in range(10)] 
print(a)

#If you wanted in refrenced form
a=[['-']*10]*10
print(a)

Example of not refrenced..

a = [['-' for col in range(10)] for row in range(10)] 
a[0][0]='change'
print(a)

Output:-

[['change', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['-', '-', '-', '-', '-', '-', '-', '-', '-', '-']]

Example of referenced..

a=[['-']*10]*10
a[0][0]='change'
print(a)

Output:-

[['change', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['change', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['change', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['change', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['change', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['change', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['change', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['change', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['change', '-', '-', '-', '-', '-', '-', '-', '-', '-'], ['change', '-', '-', '-', '-', '-', '-', '-', '-', '-']]

hyunjun · Accepted Answer · 2022-12-24 09:27:38Z

0

You can use python itertools.repeat()

from itertools import repeat
list(repeat(["-"]*10, 10))

answered Dec 24, 2022 at 9:27

hyunjun

215 bronze badges

1 Comment

tripleee Over a year ago

Please don’t post images of code, error messages, or other textual data.

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