conditional_logic.qmd

---
filters:
  - pyodide
---

# Conditional Logic

{{< video https://youtu.be/9Fix--fIVEc >}}

In the Principles of Programming section, we talked about Conditional Logic.

![](assets/2024-05-14-21-25-24.png)

In Python, we apply conditional logic using IF / ELIF / ELSE statements.  Let’s see how it works.

Let’s imagine we want to check someone’s age to determine whether they should be sent to room A or room B of our clinic :

![](assets/2024-05-14-21-25-37.png)

:::{.callout-tip}
Note the tab indentations - these are important as they indicate a block of code.  In this case, there are two blocks of code - one to run if the patient age is less than 60, one to run if that’s not the case.  In this case, each block is a single line of code, but blocks can be as long as we need.
:::

![](assets/2024-05-14-21-25-50.png)

![](assets/2024-05-14-21-26-03.png)

Let's try running this with some different age variables to see the impact!

```{pyodide-python}
age = 12

if age < 16:
    print("Please go to room A")
else:
    print("Please go to room B")
```

```{pyodide-python}
age = 55

if age < 16:
    print("Please go to room A")
else:
    print("Please go to room B")
```

If we provide an invalid option - here we provide a name as a string instead - then running the code will give us an error because it doesn't know how to compare a string (the name) to an integer (the bit on the right of our comparison operator (16)).

```{pyodide-python}
age = "Bob"

if age < 16:
    print("Please go to room A")
else:
    print("Please go to room B")
```

## Comparison Operators

There are many comparison operators in Python.  We use these to express relational statements that resolve to a Boolean - True or False.  They are therefore used in conditional logic.

![](assets/2024-05-14-21-26-22.png)

You won't be able to play along, but have a watch of this game of 'comparison operators' to learn more about comparisons.

{{< video https://youtu.be/wAAy0S96bks >}}