Python extracts the lines containing a certain string in the file and writes them into a new file

with open(r"test.log", encoding='utf-8') as f: # read data from TXT file
    list = []
    for line1 in f:
        if line1 != '\n': # remove blank lines
            l = line1.split() # This sentence uses spaces to split the file content into character segments
            list.append(l) # Put l into the array
    for item in list: # Display the lines containing a certain string under a certain character field through a for loop
        if len(item) > 1 and item[1] == 'time': # Extract the line containing the time string. Use this to judge that some lines in the file are only one character long.
            f = open("time_test.txt", "a") # Store the extracted lines into a new file, and "a" stores data in an appended way
            f.write(item[6] + "\n")