```python
lines = ["Line 1\n", "Line 2\n", "Line 3\n"]
with open('output.txt', 'w') as f:
    f.writelines(lines)  # Writes all lines at once [1][3]

# Alternative with join()
with open('output.txt', 'w') as f:
    f.write('\n'.join(lines))  # Joins with newlines automatically [1][4]

```