Lesson 10 of 12

Filter and sort: work with tables

Keep only the rows that match with Filter Rows, and put them in order with Sort Rows: top 5s, rankings and searches. Run each one, then see it as real code.

About 6 minutes · 3 parts, each with a program to try

Part 1 of 3

Filter Rows: keep the ones that match

A table is a list of rows, and each row has fields: {name: "Arun", marks: 92}.

Filter Rows makes a new list of only the rows where a condition is true, like row.marks > 80. The list it came from stays as it was.

ExampleAbove 80 Try it

Start
Create students = [{name: "Arun", marks: 92}, {name: "Priya", marks: 76}, {name: "Kavin", marks: 88}]
For each s in toppers
Repeat →
1. Tell s.name
back to the top for the next lap
End

It showsArunKavin

1from types import SimpleNamespace2
3students = [SimpleNamespace(name="Arun", marks=92), SimpleNamespace(name="Priya", marks=76), SimpleNamespace(name="Kavin", marks=88)]4toppers = []5for row in students:6    if row.marks > 80:7        toppers.append(row)8for s in toppers:9    print(s.name)

Part 2 of 3

Sort Rows: put them in order

Sort Rows makes a sorted copy: by one field, like marks, smallest or biggest first.

Fill in Keep the first to keep only the top few: 3 for the top 3.

ExampleTop 2 Try it

Start
Create students = [{name: "Arun", marks: 92}, {name: "Priya", marks: 76}, {name: "Kavin", marks: 88}]
For each s in top
Repeat →
1. Tell s.name + ": " + s.marks
back to the top for the next lap
End

It showsArun: 92Kavin: 88

1from types import SimpleNamespace2
3students = [SimpleNamespace(name="Arun", marks=92), SimpleNamespace(name="Priya", marks=76), SimpleNamespace(name="Kavin", marks=88)]4top = sorted(students, key=lambda row: row.marks, reverse=True)[:2]5for s in top:6    print(s.name + ": " + str(s.marks))

Part 3 of 3

What Filter Rows really does

Filter Rows is a shortcut for a loop you already know: For Each row, a Decision, and Change a List to add it.

This program does the same as the first one, the long way. View Code shows Filter Rows as this loop too.

ExampleAbove 80, the long way Try it

Start
Create students = [{name: "Arun", marks: 92}, {name: "Priya", marks: 76}, {name: "Kavin", marks: 88}]
Create toppers = []
For each row in students
Repeat →
1. Is row.marks > 80 true?
2. Yes →
  1. Add row.name to the end of toppers
3. No →
  nothing, just carry on
back to the top for the next lap
Tell join(toppers)
End

It showsArun, Kavin

1from types import SimpleNamespace2
3students = [SimpleNamespace(name="Arun", marks=92), SimpleNamespace(name="Priya", marks=76), SimpleNamespace(name="Kavin", marks=88)]4toppers = []5for row in students:6    if row.marks > 80:7        toppers.append(row.name)8print(", ".join(toppers))

Blocks in this lesson

Filter Rows Sort Rows

Quick check

marks is [70, 95, 80]. Sort Rows biggest first, keeping the first 2. What's left?

Practise this

World 5 challengesBuild it yourself, with three hints each.🛒 Supermarket TrolleyA Story Mode story that uses it.