How to merge an array with its array elements in Python?

Question

I have an array like below;

constants = ['(1,2)', '(1,5,1)', '1']

I would like to transform the array into like below;

constants = [(1,2), 1, 2, 3, 4, 5, 1]

For doing this, i tried some operations;

from ast import literal_eval
import numpy as np
constants = literal_eval(str(constants).replace("'",""))
constants = [(np.arange(*i) if len(i)==3 else i) if isinstance(i, tuple) else i for i in constants]

And the output was;

constants = [(1, 2), array([1, 2, 3, 4]), 1]

So, this is not expected result and I'm stuck in this step. The question is, how can i merge the array with its parent array?

I don't need convert it. I need to convert tuples has 3 values. — Ceylan B.
– Ceylan B., Commented Aug 10, 2018 at 11:50
@taras Yes it does. But it's not my problem. The problem is how to merge it with parent array. — Ceylan B.
– Ceylan B., Commented Aug 10, 2018 at 11:52

Rakesh · Accepted Answer · 2018-08-10 12:06:09Z

1

This is one approach.

Demo:

from ast import literal_eval

constants = ['(1,2)', '(1,5,1)', '1']
res = []
for i in constants:                
    val = literal_eval(i)              #Convert to python object
    if isinstance(val, tuple):         #Check if element is tuple
        if len(val) == 3:              #Check if no of elements in tuple == 3
            val = list(val)
            val[1]+=1
            res.extend(range(*val))
            continue            
    res.append(val)
print(res)

Output:

[(1, 2), 1, 2, 3, 4, 5, 1]

edited Aug 10, 2018 at 12:06

answered Aug 10, 2018 at 12:00

Rakesh

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5 Comments

Ceylan B. Over a year ago

what if the array: constants = ['(1,2)', '(1,5,1)', '1', '(0.1, 0.9, 0.1)'] ? The error is: 'float' object cannot be interpreted as an integer.

Rakesh Over a year ago

What is the expected output of ['(1,2)', '(1,5,1)', '1', '(0.1, 0.9, 0.1)'] ?

Ceylan B. Over a year ago

The expected result: [(1,2), 1, 2, 3, 4, 5, 1, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9]

Ceylan B. Over a year ago

I solved it; just change the range(*val) to np.arange(*val).

Rakesh Over a year ago

Yes...I was about to post that :)

Green Cloak Guy · Accepted Answer · 2018-08-10 11:57:42Z

I'm going to assume that this question is very literal, and that you always want to transform this:

constants = ['(a, b)', '(x, y, z)', 'i']

into this:

transformed = [(a,b), x, x+z, x+2*z, ..., y, i]

such that the second tuple is a range from x to y with step z. So your final transformed array is the first element, then the range defined by your second element, and then your last element. The easiest way to do this is simply step-by-step:

constants = ['(a, b)', '(x, y, z)', 'i']
literals = [eval(k) for k in constants]    # get rid of the strings
part1 = [literals[0]]                      # individually make each of the three parts of your list
part2 = [k for k in range(literals[1][0], literals[1][1] + 1, literals[1][2])]    # or if you don't need to include y then you could just do range(literals[1])
part3 = [literals[2]]
transformed = part1 + part2 + part3

Cendre · Accepted Answer · 2018-08-10 12:00:09Z

0

I propose the following:

res = []
for cst in constants:

    if isinstance(cst,tuple) and (len(cst) == 3):
        #add the range to the list
        res.extend(range(cst[0],cst[1], cst[2]))
    else:
        res.append(cst)

res has the result you want. There may be a more elegant way to solve it.

answered Aug 10, 2018 at 12:00

Cendre

1148 bronze badges

Comments

Andriy Ivaneyko · Accepted Answer · 2018-08-10 12:01:02Z

0

Please use code below to resolve parsing described above:

from ast import literal_eval


constants = ['(1,2)', '(1,5,1)', '1']
processed = []

for index, c in enumerate(constants):
    parsed = literal_eval(c)
    if isinstance(parsed, (tuple, list)) and index != 0:
        processed.extend(range(1, max(parsed) + 1))
    else:
        processed.append(parsed)

print processed  # [(1, 2), 1, 2, 3, 4, 5, 1]

edited Aug 10, 2018 at 12:01

answered Aug 10, 2018 at 11:52

Andriy Ivaneyko

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4 Comments

Ceylan B. Over a year ago

TypeError: isinstance expected 2 arguments, got 3

Ceylan B. Over a year ago

The result is not i wanted. The result should be; [(1,2), 1, 2, 3, 4, 5, 1]

taras Over a year ago

@AndriyIvaneyko, what if a tuple is not the first element of the list?

Andriy Ivaneyko Over a year ago

@taras item will be appended.

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