Networks

# Networks

Week 11

---

## Review

![](https://media1.giphy.com/media/v1.Y2lkPTc5MGI3NjExcmZocTNjeHRkZGJ1Z3ZueHM3NWdxd3U1ZTZvd2VteHNybWVteGlwdyZlcD12MV9naWZzX3NlYXJjaCZjdD1n/3D4HBmyRdlPotgeZbu/giphy.webp)

What does this print?

```py
scores = [85, 92, 78]
print( len(scores) )
```

```
3
```

What does this print?

```py
scores = [85, 92, 78]
scores[1] = 100
print(scores)
```

```
[85, 100, 78]
```

What is an algorithm?

A list of instructions for a specific task

What is one time through a loop called?

An iteration

How does a `while` loop know when to stop?

A boolean condition

What is wrong with this code?

```py []
print_count = 0
while print_count < 4:
    print("Hello!")
```

The condition never changes

How many times does this loop run?

```py
for _ in []:
    print("Hello, World!")
```

0

What does this print?

```py
for n in range(3):
    print(n)
```

```
0
1
2
```

When should you use a `for` loop?

When doing something for each item in a list

---

## Networks

What is a network?

> A system of lines or channels that cross or interconnect

NOTES: from American Heritage Dictionary

**Road** network

![road map](https://ontheworldmap.com/usa/state/washington/washington-road-map.jpg)

**Neural** network

![human brain](https://upload.wikimedia.org/wikipedia/commons/c/cc/Brain_model_-_Insula.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail_unscaled)

**Social** network

![Facebook](https://upload.wikimedia.org/wikipedia/en/1/12/Original-facebook.jpg?utm_source=en.wikipedia.org&utm_campaign=imageinfo&utm_content=thumbnail_unscaled)

**Cellular** network

![cell tower](https://dgtlinfra.com/wp-content/uploads/2024/01/Cell-Towers-Near-Me-Nearby-Cellular-Sites-Local-Base-Stations-Antennas-1068x598.jpg)

**Computer** network

![modem and router](https://itheroes.org/wp-content/uploads/2024/09/a-photo-of-a-modem-and-router-on-a-desk-the-modem-BfsFaSXiRyyuDcovd_ymig-UpZbXAN-TMak7m68DSAECw.png)

In a network, each computer has a unique address

```txt
127.0.0.1
```

A network interface (hardware) allows computer to send/receive data

![network interface](https://tecadmin.net/wp-content/uploads/2023/06/network-interface-controller.jpg)

A **modem** converts digital to analog signal

![CISCO modem](https://b2645180.smushcdn.com/2645180/wp-content/uploads/2023/01/Cisco-DPC3008-DOCSIS-3.0-Cable-Modem.png?lossy=1&strip=1&webp=1)

NOTES: "modulator-demodulator" converts binary to radio/telephone signal

A **router** directs traffic

![router](https://www.pcguide.com/wp-content/uploads/2023/11/Best-wired-router.jpg)

Often both devices are combined

Each computer agrees to use the same **protocol** to communicate

![handshake](https://wallpapers.com/images/hd/handshake-pictures-d6nbg7n6rnhlapmd.jpg)

NOTES: like a language, it's an agreed-upon way to talk. Think of implied response to "knock knock" jokes.

**LAN** stands for "local area network"

![Minecraft LAN mode](https://staticg.sportskeeda.com/editor/2025/02/3deec-17399429963216-1920.jpg)

Campus area network is common

![George Fox University campus](https://www.georgefox.edu/about/_assets-location/images/dji_0321.webp)

The **internet** is the most famous

![internet graph](https://upload.wikimedia.org/wikipedia/commons/d/d2/Internet_map_1024.jpg?utm_source=en.wikipedia.org&utm_campaign=index&utm_content=original)

NOTES: network visualization from 2005. Will learn more about it next week.

**Wi-Fi** is a way to connect to LAN _wirelessly_

_Wi-Fi is not the same as the internet!_

---

## Dictionaries

A _dictionary_ is a data structure in Python

It is important for web programming

NOTES: a list is a data structure that we already learned about. Dictionary is similar to JSON.

Key-value data structure

```py
data = { "name": "Rylan", "age": 27 }
```

Each key must be unique

```py
print({ "name": "Rylan", "name": "foo" })
```

```txt
{'name': 'foo'}
```

Can be accessed with square brackets

```py
data = { "name": "Rylan", "age": 27 }
print( data["name"] )
```

```txt
Rylan
```

Can be updated like a list

```py
data = { "name": "Rylan", "age": 27 }
data["name"] = "foo"
print( data["name"] )
```

```txt
foo
```

What happens when _accessing_ a key that doesn't exist?

```py
data = { "name": "Rylan", "age": 27 }
print( data["foo"] )
```

```txt
KeyError: 'foo'
```

What happens when _updating_ a key that doesn't exist?

```py
data = { "name": "Rylan", "age": 27 }
data["foo"] = "bar"
print( data )
```

```txt
{'name': 'Rylan', 'age': 27, 'foo': 'bar'}
```

Removing a dictionary item

```py
data = { "name": "Rylan", "age": 27 }
del data["age"]
print( data )
```

```txt
{'name': 'Rylan'}
```

Using with a `for` loop

```py
data = { "name": "Rylan", "age": 27 }
for key in data:
    print(key, ": ", data[key])
```

```txt
name :  Rylan
age :  27
```

---

## Exercise

- Create store inventory using dictionary
- The key is the item's name
- The value is a price
- Allow user to search for items

```txt
Enter item name: bananana
There are no items like "bananana"
```

```txt
Enter item name: ban
- Banana:  $0.49
- Bandana: $9.99
```

```py
items = {
    "Banana": 0.49,
    "Bandana": 9.99
}
search = input("Enter an item: ").lower()
items_found = 0
for key in items:
    if search in key.lower():
        items_found += 1
        print(f'{key:7}: ${items[key]:.2f}')
if items_found == 0:
    print(f'There are no items like "{search}"')
```

---

![Jimmy Fallon thats it](https://media4.giphy.com/media/v1.Y2lkPTc5MGI3NjExd2NmamM3NmR2c3RtenR3bGV5dnR1MnNyM3BzNnh3ZGNwYTFyZ2V6YyZlcD12MV9pbnRlcm5hbF9naWZfYnlfaWQmY3Q9Zw/uSZQ6WPIcpouUEpNTe/giphy.gif)