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Introduction to Arrays

Week 6 -Topic 1 Introduction to Arrays · Whatisin thislesson?

Introduction to Arrays

Week 6 -Topic 1 Introduction to Arrays

Whatisin thislesson?

  1. List
  2. Introduction to List (Recap)
  3. Processing List
  4. Using List for File Handling
  5. List with record file
  6. List with number file
  7. Multi-Dimensional List
  8. Plotting List Data with the matplotlib Package 11th January 2026 Tram Tran
8-3
  1. Lists Figure 8-6 A list of integers
  2. A list is an object that contains multiple data items.
  3. Each item that is stored in the list is called an element.

For example:

even_numbers = [2, 4, 6, 8, 10]
  • Elements are enclosed in brackets and separated by commas.
8-4

Lists Iterating Over a List with the for Loop

numbers = [99, 100, 101, 102]

for n in numbers: print n

8-5

Lists Indexing

my_list = [10, 20, 30, 40]

print my_list[index]

10 20 30 40
0 1 2 3
- 4 -3 -2 -1

my_list

8-6

Lists Slicing

days = [‘Sunday’, ‘Monday’, ‘Tuesday’, ‘Wednesday’,

‘Thursday’, ‘Friday’, ‘Saturday’]

mid_days = days[2:5] # from indexes 2 up to but not including 5

# [‘Tuesday’, ‘Wednesday’,‘Thursday’] Sunday Monday Tuesday WednesdayThursday Friday Saturday

0 1 2 3 4 5 6
- 7 -6 -5 -4 -3 -2 -1

days

8-7

Lists Finding Items in a List with in and not in Program 8-9 (in_list.py)

8-8

Lists Passing a List as an Argument to a Function Program 8-18 (total_function.py)

8-9

Lists Returning a List from a Function Program 8-19 (return_list.py)

8-10
  1. Using List for File Handling Working with Lists and Files … Saving a list as a File

Program 8-21 (writelines.py)

8-11
  1. Using List for File Handling Working with Lists and Files … Reading a list from a File

Program 8-23 (read_list.py)

7-12
  1. Using List for File Handling Concept:

The data that is stored in a file is frequently organized in records. A record is a complete set of data about an item, and a field is an individual piece of data within a record.

7-13
  1. Using List for File Handling: Processing

Records

  • A file’s data is organized into records and fields
  • Record – a complete set of data that describes one item
  • Field – a single piece of data within a record Figure 7-19 Records in a file
7-14
  1. Using List for File Handling: Processing

Records

7-15
  1. Using List for File Handling: Processing

Records class Department:

IT, HR, SALES, FINANCE = range(1, 5)
Department_names = ['IT', 'HR', 'Sales', 'Finance']

class Employee: def __init__(self, name, emp_id, department):

self.name = name
self.emp_id = emp_id
self.department = department

def __str__(self): return f"Name: {self.name}\nID: {self.emp_id}\nDepartment: {self.department}"

7-16

Save List as file from employee import Employee # Write employees to file def write_employees(file, emp_list): file.write(str(len(emp_list)) + "\n") # number of employees while index < len(emp_list): file.write(emp_list[index].name + "\n") file.write(emp_list[index].emp_id + "\n") file.write(str(emp_list[index].department) + "\n") def main(): # Create employees manually (sample data)

employees = []
count = int(input("How many employees? "))

while index < count: print("\nEmployee", index + 1)

name = input("Name: ")
emp_id = input("ID: ")
department = int(input("Department
(1-4): "))
emp = Employee(name, emp_id,

department) employees.append(emp) # Open file for writing

a_file = open("input.txt", "w")

write_employees(a_file, employees) a_file.close() print("\nEmployees saved successfully!")

if __name__ == "__main__":

main()

7-17
  1. Using List for File Handling: Processing

Records from employee import Employee, Department_names # Reads and returns a single employee from the file def get_employee(file):

name = file.readline().strip()
emp_id = file.readline().strip()
department = int(file.readline().strip())

return Employee(name, emp_id, department) # Reads and returns a list of employees from the file def get_employees(file):

emp_list = []
count = int(file.readline()) # first line =

number of employees while index < count:

emp = get_employee(file)

emp_list.append(emp) return emp_list # Prints employees def print_employees(emp_list):

total = len(emp_list)

while index < total: print("Name:", emp_list[index].name) print("ID:", emp_list[index].emp_id) print("Department:", Department_names[emp_list[index].department – 1]) print() def main():

a_file = open("input.txt", "r") # open for

reading

employees = get_employees(a_file)

print_employees(employees) a_file.close()

if __name__ == "__main__":

main()

Multi-Dimensional List

  1. Two-Dimensional Lists
  2. CONCEPT: A two- dimensional list is a list that has other lists as its elements.
  3. Why Use Two- Dimensional Lists?
  4. Two-dimensional lists are useful for working with multiple sets of data. 1-19

Two-Dimensional Lists

1-20
  1. Plotting List Data with the matplotlib Package
  2. matplotlib package is a specialized library used for generating two-dimensional charts and graphs.
  3. Installation: install it separately after Python is already on your system. 1-21

Plotting List Data with the matplotlib Package

  • matplotlib package is a specialized library used for generating two-dimensional charts and graphs.
  • Installation: install it separately after Python is already on your system. 1-22 VS Code: 1.Ctrl + Shift + P 2.Python: Select Interpreter 3.Python 3.11

Plotting List Data with the matplotlib Package

1-23

Plotting List Data with the matplotlib Package

1-24

Copyright © 2009 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

QUESTIONS

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Recap

  1. List
  2. Introduction to List (Recap)
  3. Processing List
  4. Using List for File Handling
  5. List with record file
  6. List with number file
  7. Multi-Dimensional List
  8. Plotting List Data with the matplotlib Package 1-26
1-27