python how to delete a line from a txt file and add data

Question

my program reads all txt files from a folder and convert the numbers in the txt files. one of my txt file for example is this

1 0.487500 0.751667 0.112500 0.246667
0 0.464375 0.648333 0.046250 0.083333
4 0.500000 0.352500 0.055000 0.098333

they all have the same frame like above but the rows could have less or more. so far i've been able to convert them using below code

import os


for root, dirs, files in os.walk('./'):
    for idx, file in enumerate(files):
        fname, ext = os.path.splitext(file)
        if ext in ['.txt']:
            with open((file),'r') as f:
                lines = f.readlines()
                for line in lines:
                    item = line.split(" ")
                    item[1] = float(item[1])
                    item[1] = ((item[1]) * 800 - 256) / 288
                    item[1] = '{:.6f}'.format(round(item[1],6))
                    item[1] = str(item[1])

            
                    item[2] = float(item[2])
                    item[2] = ((item[2]) * 600 - 88) / 512
                    item[2] = '{:.6f}'.format(round(item[2],6))
                    item[2] = str(item[2])

            
                    item[3] = float(item[3])
                    item[3] = ((item[3]) * 800) / 288
                    item[3] = '{:.6f}'.format(round(item[3],6))
                    item[3] = str(item[3])



                    item[4] = float(item[4])
                    item[4] = ((item[4]) * 600) / 512
                    item[4] = '{:.6f}'.format(round(item[4],6))
                    item[4] = str(item[4])

                    item = ' '.join(item)
                    print (item)

and result using the above code and the txt file is

1 0.465278 0.708985 0.312500 0.289063
0 0.401042 0.587890 0.128472 0.097656
4 0.500000 0.241211 0.152778 0.115234

which works great but i need to replace the results to the original. how would i be able to do it?