VannKit: List and Dictionary

​List and Dictionay

List and dictionary have a distinct role to play in python programming.

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​List and Dictionay

​In this lesson we will study List and Dictionary

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Let us look on each type separately, and later in the lesson we will combine them.​

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​List: Lists are written within square brackets [ ].

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​Note 1: This list consists of strings since each elements has " "

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Example 1:

thislist 1= ["apple", "banana", "cherry"]

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Example 2:

thislist 2= ["apple", "banana", "cherry", 1, 4. 6. true, false]

​Note 2: This list consists of strings, intgers and bolian values

Audio Response

State two things you learn from the watching the video.

Open Audio Recorder

Multiple Choice

What does the [ ] mean as shown below?

1

1. B = ["apple", "banana", "cherry"]

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• Line 1 are fruits

• Line 1 is a list called B

​List length

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To determine how many items a list has, use the len( ) function:

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Example: Print the number of items in the list:

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D = ["apple", "banana", "cherry"]

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print( len(D) )

​Here we are asking to print the number of items in list called 'D'

The result should be 3​

Audio Response

What is this asking?

list1 = ["apple", "banana", "cherry"]

list2 = [1, 5, 7, 9, 3]

list3 = [True, False, False]

print(len (list2))

Open Audio Recorder

Open Ended

Q1 part 1

Using the example shown below,

Create a list with four elements.

Estimate the number of elements in the list, using `len` function

Example: D = ["apple", "banana", "cherry"]

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print( len(D) )

​Extracting an element from a list

To show how to do this, we will use

thislist 2= ["apple", "banana", "cherry", 1, 4. 6. true, false]​

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Subject | Subject

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NOTES:​

1. Each item in a list is said to be ordered.

2. This means that items occupy a unique position in the list,.

3. This position starts numbering sequence: 0, 1, 2, 3, 4...​

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thislist 2= ["apple", "banana", "cherry", 1, 4. 6. true, false]​

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​index 0

​index 1

index 2

​index 7

...​

​Extracting an element from a list

Subject | Subject

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thislist 2= ["apple", "banana", "cherry", 1, 4. 6. true, false]​

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​index 0

​index 1

​index 2

​index 7

​index 3

​index 4

​index 5

• ​To extract an element from this list, all you need to know is the list position

• Let's assume you want to extract, false from the list

• "cherry holds position 7 in list called thislist 2

• ​So to extract, we will write....

  • result=thislist 2​[7]

​NOTE: The result list is similar to list 2, but it is saying that it wants only the item in index 7 of thislist 2.

​index 6

Multiple Choice

What will be printed?

list1 = ["apple", "banana", "cherry"]

list2 = [1, 5, 7, 9, 3]

list3 = [True, False, False, 2, 4, 5]

print(len (list2))

• 3

• 5

• 6

Multiple Choice

What will be printed?

list1 = ["apple", "banana", "cherry"]

list2 = [1, 5, 7, 9, 3]

list3 = [True, False, False, 2, 4, 5]

print(len (list3))

• 3

• 5

• 6

Multiple Choice

What will be printed?

list1 = ["apple", "banana", "cherry"]

list2 = [1, 5, 7, 9, 3]

list3 = [True, False, False, 2, 4, 5]

print(len (list1))

• 3

• 5

• 6

​List: Data Type

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​List items can be of any data type:

​Example 1

String, int and boolean data types:

1. list1 = ["apple", "banana", "cherry"]

2. list2 = [1, 5, 7, 9, 3]

3. list3 = [True, False, False]

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​List: Data Type

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​List items can be of any data type:

​Example 2

A list with strings, integers and boolean values:​

​list1 = ["abc", 34, True, 40, "male"]

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​We will end list for now, and start the Dictionary part of the lesson

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​Dictionary

​Dictionary is similar to list, except that Dictionary provide more information.

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Dictionary stores data values in value pairs. (that is, two at a time)

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​List vs Dictionary

​list = ["Eggs","milk", "cheese, "Yogurt", "Butter", "More Cheese"]

​Note:

Indexing starts 0,

• 1st item, "eggs' is at index 1​

• 2nd item, "milk" is at index 2​

• and so on​

​List vs Dictionary

​dictionary = {  "Eggs": "2.59",  "Milk": "3.19",  "Cheese": 4.80, "Yogert": 1.35, "Butter": 2.59, "More Cheese: 6.19}

​List vs Dictionary

​list1 = ["Eggs","milk", "cheese, "Yogurt", "Butter", "More Cheese"]

​dictionary = {  "Eggs": "2.59",  "Milk": "3.19",  "Cheese": 4.80, "Yogert": 1.35, "Butter": 2.59, "More Cheese: 6.19}

​List vs Dictionary

​dictionary = {  "Eggs": "2.59",  "Milk": "3.19",  "Cheese": 4.80, "Yogert": 1.35, "Butter": 2.59, "More Cheese: 6.19}

​list = ["Eggs","milk", "cheese, "Yogurt", "Butter", "More Cheese"]

​NOTE:

1. ​The list itemizes each items in the list

2. The dictionary gives more information, it also give the pricing information

3. The dictionary information is in pairs​

​Access Values in a Python Dictionary

​Using the key names

Items in a dictionary can be accessed using the key names.

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​Note

The Key name is the 1st item in the ordered pair

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​Example1 = { 

 "brand": "Ford",  

"model": "Mustang",  

"year": 1964}

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​In the example1 dictionary, the key names are

• " brand"

• ​"model"

• ​"year"

• ​"year"

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​Access Values in a Python Dictionary

​Using the key names

​Example1 = { 

 "brand": "Ford",  

"model": "Mustang",  

"year": 1964}

​Let's say we want to extract "Mustang" from the directory.

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The key name is "model"​

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So we will write:

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x = example1["model"]

Fill in the Blank

prices = {  "Eggs": "2.59",  "Milk": "3.19",  "Cheese": 4.80, "Yogert": 1.35, "Butter": 2.59, "More Cheese: 6.19}

Complete the statement that would assess the cost of 'Cheese' from the dictionary

x= dictionary[---------]

$$Q1\ part2$$  

Fill in the Blank

prices = {  "Eggs": "2.59",  "Milk": "3.19",  "Cheese": 4.80, "Yogert": 1.35, "Butter": 2.59, "More Cheese: 6.19}

Write the statement that would assess the cost of 'Milk' from the dictionary

$$Q1,\ part\ 2$$   

Open Ended

Create a list with four elements and extract first element from the list