read from source file one line at a time and write to target file one line at time.

#read a file and write to a file
import sys

def read_file(filename):
    file = open(filename, "r")
    lines = file.readlines()
    return lines

def write_file(filename, lines):
    file = open(filename, "w")
    for line in lines:
        file.write(line)
        
if __name__ == "__main__":
    if len(sys.argv) != 3:
        print("Usage: python read_file.py <source_file> <target_file>")
        sys.exit(1)
    source_filename = sys.argv[1]
    target_filename = sys.argv[2]
    lines = read_file(source_filename)
    lines = list(filter(lambda l: len(l.strip()) != 0, lines))
    write_file(target_filename, lines)