How to replace string occurrences in python file?

Use csv.reader with delimiter="\x01" to split by the SOH character. Then, as you read each line, split each element by "=" and keep only the values.

import csv

filedata = []
with open('file.txt', 'r') as file:
    reader = csv.reader(file, delimiter="\x01")
    for row in reader:
        # Split each item in row
        # Keep only second element of each split
        values = [item.split("=", 1)[1] for item in row]
        filedata.append(values)

print(filedata)

which gives

[['Fix1.1', '70', 'AE', '237'], 
 ['Fix1.1', '71', 'AE', '238'], 
 ['Fix1.1', '72', 'AE', '239'], 
 ['Fix1.1', '73', 'AE', '240']]

You can write this list of lists to a file using csv.writer.writerows().

with open('outfile.txt', 'w') as f:
    w = csv.writer(f)
    w.writerows(filedata)

and your output file has:

Fix1.1,70,AE,237
Fix1.1,71,AE,238
Fix1.1,72,AE,239
Fix1.1,73,AE,240

If all you care about is to read the original file and write the new file, you can combine these two operations in one loop:

import csv

filedata = []
with open('file.txt', 'r') as file_in, open('outfile.txt', 'w') as file_out:
    reader = csv.reader(file_in, delimiter="\x01")
    writer = csv.writer(file_out)
    for row in reader:
        # Split each item in row
        # Keep only second element of each split
        values = [item.split("=", 1)[1] for item in row]
        # filedata.append(values)
        # Instead of appending to a container list,
        # Write to the output file
        writer.writerow(values)