Issue with itertools.product that not list as expected

Question

Python itertools.product module not working as expect when I'm extracting string "[1,2], [3,4], [5,6,7], [8,9]" from a json object here:

},
 "combos_matrix": "[1,2], [3,4], [5,6,7], [8,9]"
},

But it's working when I put directly numbers in ():

list(itertools.product([1,2], [3,4], [5,6,7], [8,9]))

Here is my results when I extract data from json and try the function

Json sample:

},
"combos_matrix": "[1,2], [3,4], [5,6,7], [8,9]"
},

Code by using json object:

combos_matrix = map_json["world"]["combos_matrix"]
print(combos_matrix)
combos_list = list(itertools.product(combos_matrix))
print(combos_list)

Output:

[1,2], [3,4], [5,6,7], [8,9]
[('[',), ('1',), (',',), ('2',), (']',), (',',), (' ',), ('[',), ('3',), (',',), ('4',), (']',), (',',), (' ',), ('[',), ('5',), (',',), ('6',), (',',), ('7',), (']',), (',',), (' ',), ('[',), ('8',), (',',), ('9',), (']',)]

What I'm expecting and this is the result when I give the function directly the list of numbers:

Code:

combos_list = list(itertools.product([1,2], [3,4], [5,6,7], [8,9]))
print(combos_list)

Output:

[(1, 3, 5, 8), (1, 3, 5, 9), (1, 3, 6, 8), (1, 3, 6, 9), (1, 3, 7, 8), (1, 3, 7, 9), (1, 4, 5, 8), (1, 4, 5, 9), (1, 4, 6, 8), (1, 4, 6, 9), (1, 4, 7, 8), (1, 4, 7, 9), (2, 3, 5, 8), (2, 3, 5, 9), (2, 3, 6, 8), (2, 3, 6, 9), (2, 3, 7, 8), (2, 3, 7, 9), (2, 4, 5, 8), (2, 4, 5, 9), (2, 4, 6, 8), (2, 4, 6, 9), (2, 4, 7, 8), (2, 4, 7, 9)]

Can you help on this guy, I guess I'm missing something.

If it's under your control, you might want to fix the way the data gets created: you probably want `combos_matrix to be a list of lists rather than a string — Thierry Lathuille
– Thierry Lathuille, Commented Mar 24, 2024 at 21:18
What does the documentation of the data say about the format of that string? — no comment
– no comment, Commented Mar 24, 2024 at 22:09

meshkati · Accepted Answer · 2024-03-24 21:15:17Z

1

Extracting combos_matrix from JSON objects makes it a string representation of the list, but you need the actual list, you can get it from json.loads():

combos_matrix = map_json["world"]["combos_matrix"]
print(combos_matrix)

combos_matrix_json = f'[{combos_matrix}]'

combos_list = json.loads(combos_matrix_json)

combos_result = list(itertools.product(*combos_list))
print(combos_result)

Output:

[1,2], [3,4], [5,6,7], [8,9]
[(1, 3, 5, 8), (1, 3, 5, 9), (1, 3, 6, 8), (1, 3, 6, 9), (1, 3, 7, 8), (1, 3, 7, 9), (1, 4, 5, 8), (1, 4, 5, 9), (1, 4, 6, 8), (1, 4, 6, 9), (1, 4, 7, 8), (1, 4, 7, 9), (2, 3, 5, 8), (2, 3, 5, 9), (2, 3, 6, 8), (2, 3, 6, 9), (2, 3, 7, 8), (2, 3, 7, 9), (2, 4, 5, 8), (2, 4, 5, 9), (2, 4, 6, 8), (2, 4, 6, 9), (2, 4, 7, 8), (2, 4, 7, 9)]

answered Mar 24, 2024 at 21:15

meshkati

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Comments

Andrej Kesely · Accepted Answer · 2024-03-24 22:20:30Z

1

The type of the dictionary value is string, so you need to convert this string to a list first (NOTE: your string is missing the initial [ and final ], so when converting this string to a list it needs to be added).

For string->list conversion you can use ast.literal_eval:

from ast import literal_eval
from itertools import product

dct = {"combos_matrix": "[1,2], [3,4], [5,6,7], [8,9]"}

lst = literal_eval(f"[{dct['combos_matrix']}]")
for p in product(*lst):
    print(p)

Prints:

(1, 3, 5, 8)
(1, 3, 5, 9)
(1, 3, 6, 8)
(1, 3, 6, 9)
(1, 3, 7, 8)
(1, 3, 7, 9)
(1, 4, 5, 8)
(1, 4, 5, 9)
(1, 4, 6, 8)
(1, 4, 6, 9)
(1, 4, 7, 8)
(1, 4, 7, 9)
(2, 3, 5, 8)
(2, 3, 5, 9)
(2, 3, 6, 8)
(2, 3, 6, 9)
(2, 3, 7, 8)
(2, 3, 7, 9)
(2, 4, 5, 8)
(2, 4, 5, 9)
(2, 4, 6, 8)
(2, 4, 6, 9)
(2, 4, 7, 8)
(2, 4, 7, 9)

edited Mar 24, 2024 at 22:20

answered Mar 24, 2024 at 21:14

Andrej Kesely

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5 Comments

no comment Over a year ago

I think it would be good to say why you convert it to a list first, instead of evaluating it to a tuple.

no comment Over a year ago

I mean, someone might think you could just do the simpler literal_eval(dct['combos_matrix']), without realizing why you didn't do that.

Andrej Kesely Over a year ago

@nocomment I've updated my answer and put a note about it there.

no comment Over a year ago

Hmm, that explains a detail of the list conversion, not why you decided to convert to a list. Now I wonder whether you actually do have a reason for that other than that is the only thing you thought of. Do you realize that using literal_eval(dct['combos_matrix']) does work here? And do you realize why it's still bad?

no comment Over a year ago

In case someone ever wonders: the issue with literal_eval(dct['combos_matrix']) is that it wouldn't work if there weren't four sublists but only one or zero.

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