error in CSV resetting with seek(0)

[Rahul Gupta]

consider the following code
import csv
import numpy as np

with open("D:\PHD\obranking\\demo.csv", mode='r') as csv_file1, open("D:\PHD\obranking\\demo.csv", mode='r') as csv_file2:
    csv_reader1 = csv.DictReader(csv_file1)
    csv_reader2 = csv.DictReader(csv_file2)


    filename = "cell_split_demo.csv"
    with open("D:\PHD\obranking\\cell_split_demo.csv", 'w') as csvfilew1:
        fields = (range(0, 300))
        csvwriter1 = csv.DictWriter(csvfilew1, fieldnames=fields)
        csvwriter1.writeheader()

        for i, row in enumerate(csv_reader1):
            print(f"value_i({i}) label({row['label']})")
            for j, line in enumerate(csv_reader2):
                if j <= i:
                    matrixrows[j] = []
                    if row['label'] != line['label']:
                        print(f"value_j({j})Unequal label({line['label']})")
                    else:
                        print(f"value_j({j})   equal label({line['label']})")
                        pass
                else:
                    break
            csv_file2.seek(0)
Here is some of the out_put samples
value_i(0) label(BW)
value_j(0)   equal label(BW)
value_i(1) label(BW)
value_j(0)   Unequal label(label)
value_j(1)   equal label(BW)
value_i(2) label(BW)
value_j(0)   Unequal label(label)
value_j(1)   equal label(BW)
value_j(2)   equal label(BW)
You can see for j=0 while i goes from 1 to n it is not able to acess line['label'] value.
Kindly help what is wrong with this?