change first line of a file in python

Question

I only need to read the first line of a huge file and change it.

Is there a trick to only change the first line of a file and save it as another file using Python? A

Answer 1

An alternate solution that does not require iterating over the lines that are not of interest.

def replace_first_line( src_filename, target_filename, replacement_line):
    f = open(src_filename)
    first_line, remainder = f.readline(), f.read()
    t = open(target_filename,"w")
    t.write(replacement_line + "\n")
    t.write(remainder)
    t.close()