with open("test.txt") as f: lines = f.readlines() lines # ['This is the first line.\n', 'This is the second line.\n'] lines = "This is the line that's replaced.\n" lines # ["This is the line that's replaced.\n", 'This is the second line.\n'] with open("test.txt", "w") as f: f.writelines(lines)
Here is what the above code is Doing:
1. Open the file in read mode.
2. Read the lines into a list.
3. Modify the first line.
4. Open the file in write mode.
5. Write the modified lines to the file.