Batch Output the Right Way
Buffer with a list and join to print fast.
Batch Output the Right Way is a free Coding Interview Prep lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Coding Interview Prep learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Output Can Be Slow Too
Just like reading, writing matters. Calling print() thousands of times flushes repeatedly and can quietly cost you the time limit.
Collect, Then Print
The fix is to gather your answers in a list first, then send them out in a single write at the end.
out = []Append Each Answer
Inside your loop, push each result onto the list with append instead of printing it on the spot.
out.append(str(answer))Strings Only, Please
join works on text, so convert numbers to strings before storing them, or convert at join time.
out.append(str(x))Join Into One Block
Glue the list together with join, using a newline so each answer lands on its own line.
result = "\n".join(out)Print It All at Once
Now a single print(result) sends every answer in one go, far faster than many small prints.
print("\n".join(out))Skip str with a Generator
You can convert on the fly: pass a generator of str() calls straight into join, no separate step needed.
print("\n".join(str(x) for x in out))Space-Separated Output
Need values on one line? Join with a space instead of a newline to print them side by side.
print(" ".join(map(str, row)))Use sys.stdout for More Speed
For the very fastest output, write directly with sys.stdout.write, which skips print() formatting.
import sys
sys.stdout.write(result)Remember the Trailing Newline
sys.stdout.write does not add a line break, so append a newline yourself if the judge expects one.
sys.stdout.write(result + "\n")When a Few Prints Are Okay
If you only output a line or two, plain print() is fine. Batch only when the answer count is large.
Quick Check
Why bother buffering output?
Recap: Batch Output
You learned to buffer answers in a list and emit them with one join-and-print. Same idea as fast input, applied to the write side. 🖨️
Frequently asked questions
Is the “Batch Output the Right Way” lesson free?
Yes — the full text of “Batch Output the Right Way” is free to read here on the web, and the Coding Interview Prep course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Coding Interview Prep course, upgrade to CoddyKit PRO.
What will I learn in “Batch Output the Right Way”?
Buffer with a list and join to print fast. You practise Coding Interview Prep with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Coding Interview Prep?
No prior experience is required. Coding Interview Prep on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Batch Output the Right Way” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Coding Interview Prep lesson?
Yes. Every Coding Interview Prep lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- input() vs sys.stdin Showdown
- Parse Many Numbers on One Line
- Batch Output the Right Way
- Read N Lines and Edge Cases