If I have a list like:
a = ['AB', ['CD', 'DE'], 'FG']
How do I transform it to a 2D list as shown:
[['AB', 'CD', 'FG'], ['AB', 'DE', 'FG']]
Using itertools.product also expands 'AB' to 'A', 'B'.
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Shankar Bhagwan
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No, that gives [('A', 'CD', 'F'), ('A', 'CD', 'G'), ('A', 'DE', 'F'), ('A', 'DE', 'G'), ('B', 'CD', 'F'), ('B', 'CD', 'G'), ('B', 'DE', 'F'), ('B', 'DE', 'G')] – Shankar Bhagwan Sep 11 '17 at 00:07
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The only one example is not clear enough to know what you need to do in the general case: can you have more nested lists, with various depth? How would you handle them? – Julien Sep 11 '17 at 00:09
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No, there is only two level of nesting. – Shankar Bhagwan Sep 11 '17 at 00:10
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1But can you have for example `['AB',['CD',EF'],['GH','IJ','KL']]`? – Julien Sep 11 '17 at 00:11
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No. There can be only list with in the parent list. – Shankar Bhagwan Sep 11 '17 at 00:12
2 Answers
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You can use itertools.product as follows:
>>> list(itertools.product(*(x if isinstance(x, list) else [x] for x in a)))
[('AB', 'CD', 'FG'), ('AB', 'DE', 'FG')]
Here we simply take the product, where we first transform singletons such as 'AB' into a list ['AB'].
If you require a list of lists for your output, simply transform them:
>>> [list(x) for x in itertools.product(
... *(x if isinstance(x, list) else [x] for x in a))]
[['AB', 'CD', 'FG'], ['AB', 'DE', 'FG']]
donkopotamus
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Thanks - is there a way to keep it a list of list instead of a list of tuple. – Shankar Bhagwan Sep 11 '17 at 00:15
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I remember in my first days, Googling how to get a list of this to a list of that, and a list of that to a list of the other, and split, and join, and blah blah. Oh, and then...regex can do it all! And later...no! Don't use regex! *Hehe...* – Sep 11 '17 at 00:29
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Here's what I came up with:
b = []
for i in range(len(a)):
if type(a[i]) is list:
for j in range(len(a[i])):
b.append(a[:i] + [a[i][j]] + a[i+1:])
Jared Jensen
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