Writing list and list of list inside the same file in Python

Question

I have a file say, file1.txt which looks something like below.

27,28,29,30,1,0.67
31,32,33,34,1,0.84
35,36,37,38,1,0.45
39,40,41,42,1,0.82
43,44,45,46,1,0.92
43,44,45,46,1,0.92
51,52,53,54,2,0.28
55,56,57,58,2,0.77
59,60,61,62,2,0.39
63,64,65,66,2,0.41
75,76,77,78,3,0.51
90,91,92,93,3,0.97

Where the last column is the fitness and the 2nd last column is the class. Now I read this file like :

rule_file_name = 'file1.txt'
rule_fp = open(rule_file_name)

list1 = []
for line in rule_fp.readlines():
    list1.append(line.replace("\n","").split(","))

Then a default dictionary was created to ensure the rows are separated according to the classes.

from collections import defaultdict

classes = defaultdict(list)
for _list in list1:
    classes[_list[-2]].append(_list)

Then they are paired up within each class using the below logic.

from random import sample, seed
seed(1)
for key, _list in classes.items():
    _list=sorted(_list,key=itemgetter(-1),reverse=True)

    length = len(_list)
    middle_index = length // 2
    first_half = _list[:middle_index]
    second_half = _list[middle_index:]
    result=[]
    result=list(zip(first_half,second_half))

Later using the 2 rows of the pair, a 3rd row is being created using the below logic:

ans=[[random.choice(choices) for choices in zip(*item)] for item in result]

So if there were initially 12 rows in the file1, that will now form 6 pairs and hence 6 new rows will be created. I simply want to append those newly created rows to the file1 using below logic:

list1.append(ans)
print(ans)
    
with open(f"output.txt", 'w') as out:
    new_rules = [list(map(str, i)) for i in list1]
    for item in new_rules:
        out.write("{}\n".format(",".join(item)))
        #out.write("{}\n".format(item))

But now my output.txt looks like:

27,28,29,30,1,0.67
31,32,33,34,1,0.84
35,36,37,38,1,0.45
39,40,41,42,1,0.82
43,44,45,46,1,0.92
43,44,45,46,1,0.92
51,52,53,54,2,0.28
55,56,57,58,2,0.77
59,60,61,62,2,0.39
63,64,65,66,2,0.41
75,76,77,78,3,0.51
90,91,92,93,3,0.97
['43', '44', '41', '46', '1', '0.82'],['27', '28', '45', '46', '1', '0.92'],['35', '36', '33', '38', '1', '0.84']
['55', '60', '57', '58', '2', '0.77'],['51', '64', '53', '66', '2', '0.28']
['75', '91', '77', '93', '3', '0.51']

But my desired outcome is:

27,28,29,30,1,0.67
31,32,33,34,1,0.84
35,36,37,38,1,0.45
39,40,41,42,1,0.82
43,44,45,46,1,0.92
43,44,45,46,1,0.92
51,52,53,54,2,0.28
55,56,57,58,2,0.77
59,60,61,62,2,0.39
63,64,65,66,2,0.41
75,76,77,78,3,0.51
90,91,92,93,3,0.97
43,44,41,46,1,0.82
27,28,45,46,1,0.92
35,36,33,38,1,0.84
55,60,57,58,2,0.77
51,64,53,66,2,0.28
75,91,77,93,3,0.51

That isn't a text file, its a csv file and you'd find it much easier to import it as a csv file — Sayse
– Sayse, Commented Apr 11, 2022 at 7:08
Can you guide me in case of the above code, if I change the extension to .csv then how the code will be modified! Or what are the added benefits I am going to get! — Dev
– Dev, Commented Apr 11, 2022 at 7:14
You don't need to change the extension, even if you've called it a text file its still a csv file in its contents, field names for a start so you can read each line in as a dictionary with actual keys rather than hard to explain logic — Sayse
– Sayse, Commented Apr 11, 2022 at 7:24
Okay I got the logic, and understood. But for now just for the above case can you give me a solution please, else I need to change at different places and just for this case I want to keep this convention fixed. — Dev
– Dev, Commented Apr 11, 2022 at 10:19
Maybe you should do not list1.append(ans), but list1.extend(ans)? — Danil Kononyhin
– Danil Kononyhin, Commented Apr 11, 2022 at 10:50

Giovanni Tardini · Accepted Answer · 2022-04-11 08:15:40Z

1

I would use numpy, it is flexible and compact.

import numpy as np

fin = 'file1.txt'
col1, col2, col3, col4, jclass, fitness = np.loadtxt(fin, unpack=True, delimiter=',')
rows = np.column_stack((col1, col2, col3, col4, jclass, fitness))

print(rows[0])
print(rows[-1])
print(fitness)

Then apply your logic to the rows array

answered Apr 11, 2022 at 8:15

Giovanni Tardini

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1 Comment

Dev Over a year ago

Can you just give me the solution for the above case which is stated in the question! From the next time onward I will follow this approach.

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