How can i look for a string in a file row by row without using readlines().
if string found then write the line in another file.
Basically I am trying to extract rows that have a specific string in them.
If there are a varying number of lines to read, readline() is not recommended, once you'll have to check if the end of file was reached.
Using a simple for loop, you can get the result you want:
file = open('your_file.txt', 'r') lines =  # Initialize output array for line in file: if "YOUR STRING" in line: lines.append(line) # Here you will have all the "selected" lines in the lines array # Now, you can write to the output file out_file = open('output_file.txt', 'w') for line in lines: out_file.write(line)
Hope it helps.