slides-01-02.qmd

---
title: "python basics (slides)"
format: revealjs
slide-number: true
---

# CSc 110 Python Basics

## CS Buddy Mentor Program Sign-Up

![sign-up QR Code](images/csBuddy.jpeg)

## Announcements

-   Sign-up for your lab session at [xinchenyu.github.io/csc110-spring2025/short-projects.html](https://xinchenyu.github.io/csc110-spring2025/short-projects.html)
-   My office hours changed to Wednesday 10:30am-12:00pm.
-   Full schedule for office hours can be found at [xinchenyu.github.io/csc110-spring2025/tas.html](https://xinchenyu.github.io/csc110-spring2025/tas.html)
-   Next lecture is Jan 22, next Wednesday.

## Did you set up your workspace?

-   Did you download Python 3?
-   Did you download VS Code (or PyCharm, or Mu)?
-   If not, that's fine, you can use [vscode.dev](https://vscode.dev/)

# What is a program?

## The `print` function

-   What does the print function do?

## The `print` function

-   `print()` sends characters (strings) to the **standard output**
-   By default, the **standard output** of a python program goes to the console.

```{python}
#| echo: true
print("some characters")
```

<br />

```{python}
#| echo: true
print('some characters')
```

## String operations

String concatenation:

-   What will the standard output display when the code below is run?

```{python}
#| echo: true
#| eval: false
print("hello" + "world")
```

## String operations

In your groups, try the following operations:

-   String repetition: `"abc" * 4`
-   String concatenation with `+` and `,`. What is the difference?
-   Combine both repetition and concatenation to print the following:

```{python}
#| echo: false
#| eval: true
print("They sang", "Aa" * 10)
```

## String operations 

solution 1:
```{python}
#| echo: true
#| eval: true
print("They sang", "Aa" * 10)
```

solution 2:
```{python}
#| echo: true
#| eval: true
print("They", "sang", "Aa" * 10)
```

solution 3:
```{python}
#| echo: true
#| eval: true
print("They" + " "  + "sang" + " " + "Aa" * 10)
```

## Multiple `print` statements

-   What will the standard output display when the code below is run?

```{python}
#| echo: true
#| eval: false
print('Are')
print('You')
print('In')
print('College?')
```

## Multiple `print` statements

-   By default, the `print` function moves the cursor to the next line after printing, unless you specify otherwise.

```{python}
#| echo: true
#| eval: true
print('Are', end = ' ')
print('You', end = ' ')
print('In', end = ' ')
print('College?', end = ' ')
```

What other characters can you use for values for the `end` parameter?

## Dealing with special characters

Write a simple program that prints the following output to the python console:

<br />

```{=html}
<pre style="font-size: 30px">

   He said, "What's up?" 
   Joe's friend didn't reply.

</pre>
```

## Dealing with special characters 

double quotes:
```{python}
#| echo: true
#| eval: true
print("He said, \"What's up?\"")
print("Joe's friend didn't reply.")
```

single quotes:
```{python}
#| echo: true
#| eval: true
print('He said, "What\'s up?"')
print('Joe\'s friend didn\'t reply.')
```

# Variables

## Variables and assignment

-   Variables are names in a program that represent a stored value
-   We can assign names to particular values in our program
-   When we give a value a name, or update the value stored in a variable, this is called assigning a variable

## Demonstration of variable assignment

Variable assignment does not produce any output to the console. Run the following code:

```{python}
#| echo: true
#| eval: false
first_name = "Mary"
family_name = "Silva"
```

How would we print these variables?

## Variables improve readability

Without variables:
```{python}
#| echo: true
#| eval: true
print("The total price is", 100 * 1.08)
```

With variables:
```{python}
#| echo: true
#| eval: true
base_price = 100
tax_rate = 1.08
total_price = base_price * tax_rate
print("The total price is", total_price)
```


## Basic Types

-   string: `"hello"` or `'hello'`
-   integer: `3`
-   float: `3.14`
-   bool: `True` or `False`

Use the function `type()` with each literal type.

## Operations

-   `+` : plus 

-   `-` : minus

-   `*` : multiple

-   `/` : divide

-   `**` : power

-  `//` : divide and floor

-  `%` : modulos
   
<br />


## Operations - examples

```{python}
#| echo: true
#| eval: true
print(10 + 5 - 5) # addition and subtraction
print(10 * 5 / 4) # multiplication and division
print(25 ** 2) # square 
print(25 ** 0.5) # square root 
print(13 // 4) # division and round down to the nearest integer
print(13 % 4) # remainder 
```

# Order of Operations

## PEMDAS

-   What does PEMDAS stand for?
-   The operator precedence:
    -   **P**arentheses
    -   **E**xponentiation
    -   **M**ultiplication and **D**ivision (including // and %)
    -   **A**ddition and **S**ubtraction

## PEMDAS

What value will each of these variables take on? No computers!

```{=html}
<pre>
a1 = 5 /  5 * 10  * 5
a2 = 5 / (5 * 10) * 5

b1 = 5 *  10 - 2
b2 = 5 * (10 - 2)

c = (3 // (4 // 5)) + 1
</pre>
```

## PEMDAS -- answer

```{python}
#| echo: true
#| eval: true
a1 = 5 /  5 * 10  * 5
a2 = 5 / (5 * 10) * 5

b1 = 5 *  10 - 2
b2 = 5 * (10 - 2)

# c = (3 // (4 // 5)) + 1 ERROR -- Zero Division

print(a1)
print(a2)
print(b1)
print(b2)
```

Note that the division operator returns a float even when both numerator and denominator are integers


# Rounding numbers with built-in function `round()`

## `round()`

Use the round() function to get a floating-point number rounded to the specified number of decimals.

Syntax:

```{python}
#| echo: true
#| eval: false
round(number, ndigits*)
```

The number of digits (`ndigits`) is optional, but we will often round number to two decimals:

```{python}
#| echo: true
#| eval: true
round(392.68750000000006, 2)
```

## `round()`

Use the round() function to get a floating-point number rounded to the specified number of decimals.

Syntax:

```{python}
#| echo: true
#| eval: false
round(number, ndigits*)
```

Rounding is done toward the nearest even choice:

```{python}
#| echo: true
#| eval: true
print(round(51.6))
print(round(51.4))
print(round(51.5))
print(round(50.5))
```


## Operations and Variable Assignments

Variable assignments are not like math --- they can appear in equations that make no mathematical sense.

<br />

```{python}
#| echo: true
#| eval: false
x = 5
print(x)
x = x + 2
print(x)
```

<br />

`x = x + 2` means "take the current value of x, add it with 2, and assign the resulting value (7) to x as its new value."

## Combining variables and operations

Write code to calculate the area of a circle when radius is 3:

1.  Assign integer 3 to radius
2.  Calculate the area (use $\pi$ as 3.1415) and round it to two decimals
3.  Print the area

## Comments

Comments are text that is meant to be read, but not executed. The purpose is to improve readability.

```{python}
#| echo: true
#| eval: true
# assign a radius value
radius = 3
# compute the area of a circle and round to two decimals
area = round(3.1415 * radius ** 2, 2)
# print the area
print(area)
```


## Questions

-  What if we want to get the area of circles when the radius is 1, 2, 3, 4 and 5?
-  Can we do it more efficiently?


## Quiz 02

<center>
<div class="cleanslate w24tz-current-time w24tz-large" style="display: inline-block !important; visibility: hidden !important; min-width:300px !important; min-height:145px !important;"><a href="//24timezones.com/Tucson/time" style="text-decoration: none" class="clock24" id="tz24-1695057604-c1393-eyJob3VydHlwZSI6IjEyIiwic2hvd2RhdGUiOiIwIiwic2hvd3NlY29uZHMiOiIwIiwiY29udGFpbmVyX2lkIjoiY2xvY2tfYmxvY2tfY2I2NTA4ODZjNDg0OWVlIiwidHlwZSI6ImRiIiwibGFuZyI6ImVuIn0=" title="World Time :: Tucson" target="_blank" rel="nofollow"></a>current time<div id="clock_block_cb650886c4849ee"></div></div>
<script type="text/javascript" src="//w.24timezones.com/l.js" async></script>
</center>

You have 5 minutes to complete the quiz.