How to split list based on characters and then make sub-lists?

Question

How do I split a list into sub-lists, and then further split that to make each character an independent value?

I need to do this all inside of Python, version 3.6.5. The list will be in integers.

I need to convert

[123, 456]

into

[[1,2,3], [4,5,6]]

EDIT:

And after I have done that, how do I print the first character of the first sublist?

Note: Splitting integer in Python? and Turn a single number into single digits Python don't solve or answer my problem, as they do not explain how to make sub-lists out of them.

More [here](https://stackoverflow.com/questions/1906717/splitting-integer-in-python). Sometimes, a little search helps and is quicker than posting question which shows no research effort and no attempt like yours — Sheldore, Dec 29 '18 at 17:43
*"they do not explain how to make sub-lists"* - so what? They show you how to process one number, so then you just need to apply the same logic to each of them in the list. — jonrsharpe, Dec 29 '18 at 17:51
What have *you tried* to get the first character of the first sub list, and what is the problem with it? This isn't a code-writing service. — jonrsharpe, Dec 29 '18 at 18:21
Please don't change your question after it has been answered and you have accepted an answer. — jpp, Dec 29 '18 at 21:01

score 2 · Accepted Answer · edited Dec 29 '18 at 19:12

2

For example, using list comprehension:-

my_list = ['123', '456']
[list(x) for x in my_list]

If my_list is a list of integers:-

my_list = [123, 456]
[[int(x) for x in str(n)] for n in my_list]

edited Dec 29 '18 at 19:12

Arihan Sharma - Sir John A Mac

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answered Dec 29 '18 at 17:39

Tom Ron

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`my_list = ['123', '456']`? The OP never said that the input is strings. Why are you making this assumption out of nowhere? You should add explanation similar to "If my_list is a list of integers-" for strings – Sheldore Dec 29 '18 at 17:45
Please see my full answer – Tom Ron Dec 29 '18 at 17:45
Will this divide them into sub-lists though? – Arihan Sharma - Sir John A Mac Dec 29 '18 at 17:47
@ArihanSharma-SirJohnAMac: Try the code and check the output – Sheldore Dec 29 '18 at 17:49
yes it will, I suggest reading more about list comprehension - https://www.pythonforbeginners.com/basics/list-comprehensions-in-python – Tom Ron Dec 29 '18 at 17:49
Checked, it just outputs `[123, 456]`. – Arihan Sharma - Sir John A Mac Dec 29 '18 at 17:53
Did you check my_list or did you check the output? (it does not assign the result to any variable) – Tom Ron Dec 29 '18 at 17:54
@TomRon You forgot to re-assign `my_list`. – Arihan Sharma - Sir John A Mac Dec 29 '18 at 17:54
@TomRon Also: This takes a lot of time. Is there a faster way? – Arihan Sharma - Sir John A Mac Dec 29 '18 at 17:55
It is your call what to do with the result. I have to think regarding faster way but not sure I have the time to compare several implementations – Tom Ron Dec 29 '18 at 17:58
@TomRon Now how do I print the first character of the first sublist? – Arihan Sharma - Sir John A Mac Dec 29 '18 at 17:59

score 2 · Answer 2 · answered Dec 29 '18 at 17:43

2

A simple list comprehension will do, the idea is iterate over the characters in the string representation of the numbers:

[[int(x) for x in str(s)] for s in l]

answered Dec 29 '18 at 17:43

Netwave

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Will this divide them into sub-lists though? – Arihan Sharma - Sir John A Mac Dec 29 '18 at 17:48
@ArihanSharma-SirJohnAMac, Indeed, that is why we have a list within the list. – Netwave Dec 29 '18 at 17:49
Now how do I print the first character of the first sublist? – Arihan Sharma - Sir John A Mac Dec 29 '18 at 17:59

How to split list based on characters and then make sub-lists?

2 Answers2