Using multiple conditions

When you use multiple conditions in a list comprehension, it means you are adding extra rules about which items should go into the list.

Syntax:

[x for x in range(20) if x % 2 == 0 and x % 3 == 0]

Let’s dissect it:

What’s Happening Here?

The goal is to create a list of numbers from 0 to 19 that satisfy two conditions:

1. The number is divisible by 2 (even number).
2. The number is divisible by 3.

Step-by-step walkthrough

Imagine you’re going through numbers 0 to 19 one by one:

1. For each number (x), check if it’s divisible by 2 (no remainder).
2. Then, check if it’s also divisible by 3.
3. If both conditions are true, add the number to the new list.

Example in action

Let’s work it out for range(20) (numbers 0 to 19):

| Number | Divisible by 2? | Divisible by 3? | Added to List? |
|--------|------------------|------------------|----------------|
| 0      | Yes              | Yes              | ✅              |
| 1      | No               | No               | ❌              |
| 2      | Yes              | No               | ❌              |
| 3      | No               | Yes              | ❌              |
| 4      | Yes              | No               | ❌              |
| 5      | No               | No               | ❌              |
| 6      | Yes              | Yes              | ✅              |
| 7      | No               | No               | ❌              |
| 8      | Yes              | No               | ❌              |
| 9      | No               | Yes              | ❌              |
| 10     | Yes              | No               | ❌              |
| 11     | No               | No               | ❌              |
| 12     | Yes              | Yes              | ✅              |
| ...    | ...              | ...              | ...            |

The final list is:

[0, 6, 12, 18]

Why Use and?

The and keyword ensures that both conditions must be true for a number to be included:

Real-Life analogy

Imagine you’re picking players for a game. Your rules are:

1. The player must be taller than 180 cm.
2. The player must be younger than 25 years.

You only select players who meet both conditions. Anyone who doesn’t fit both is skipped.