Element of List of list to List

user_4359303 0
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I have a list of list(tuple of tuple?) of number

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

I want to transform in:

(123,456,789)

I did with this code, can you suggest to me a better way to do it?

listacomb = []
for list in permdue:
    for number in list:
        numerix += "".join(str(number))
    listacomb.append(numerix)
    numerix=""
return listacomb
list-comprehension list python
3 Answers

You can do a list comprehension:

data = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
output = tuple([int("".join(map(str, inner_list))) for inner_list in data])
print(output)

Output:

(123, 456, 789)

References:

user_31294140

Here is a math approach to doing this. We can iterate each sublist backwards and build out the desired number.

permdue = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
listacomb = []

for list in permdue:
    list = reversed(list)
    m = 1
    numerix = 0
    for number in list:
        numerix += number * m
        m = m * 10
    listacomb.append(numerix)

print(listacomb)  # [123, 456, 789]

This approach avoids the performance penalizing string solution. It works, for example, by taking [1, 2, 3] and computing 3 + 20 + 100, to obtain 123.

user_18632290

It can be done without reversal like this:

permdue = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
listacomb = []

for p in permdue:
    n = 0
    for p_ in p:
        n = n * 10 + p_
    listacomb.append(n)
print(listacomb)

Output:

[123, 456, 789]
user_175803810
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