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# Conditionals

---

CS 65 // 2021-03-02

## Extra Credit Activities
- MathCS Seminar (Dr. Enes Akbuga)
    + **Topic:** Mathematics Education
    + **When:** Friday, 2:00pm to 3:00pm
    + **Where:** Zoom (email me for the link)
- [Global Citizen Forum](https://www.drake.edu/diversity/initiatives/globalcitizenforum2021/)
    + Conference on equity and inclusion in higher ed
    + March 3-5

# Questions
## ...about anything?

# Conditionals

## Conditionals
- Conditionals allow us to ask **true/false questions** about the state of our program and based on the answer to the question, do something specific
- **Is the lid of the PB still on?**
    + If so, call the “take off lid” subroutine before continuing
- **Did the user enter bad input?**
    + If so, ask them to type in something not broken
    + Otherwise, continue with the program normally

## Conditionals
- Conditionals in Python have the following form:

```py
if first_condition:
    print("First condition was true!")
elif second_condition:
    print("First condition was false AND second was true!")
else:
    print("None of the above conditions were true!")
```

- 
 The conditions must be expressions that evaluate to `True` or `False`
- 
 These are called **Boolean expressions**
- 
 The `elif` and `else` parts are optional and may be omitted

# Boolean Values

## The `bool` Type
- A **bool** in Python is a value that is `True` or `False`
- 
 **Purpose:**
    + Allow us to evaluate True/False questions and handle cases separately
- 
 **Express:**
    + `True`, `False`
- 
 **Operations:**
    + 
 `and`, `or`, `not`, ...

## Boolean Expressions
- **Boolean expressions** are expressions that eventually evaluate to a `bool`
- 
 Boolean expressions can consist of **and** and **or** operations
    + `x and y`
    + `x or y`
- 
 **Comparison operators** also return bools
    + `x < 3`
    + `y == "hello"`
    + `z != 5`

## Boolean Expressions
- You can also use comparators on strings
    + What do you think `"hello` < "world" will do?
- 
 What happens if you combine operations into more complicated expressions?
    + (3 < 7) and (7 == 6)
    + (3 < 7) or (7 == 6)

# Self Check

# Lab Time