5 Levels of Writing Python Lists

 

Level 1: Basic List Creation and Access

# Creating a list

fruits = ['apple', 'banana', 'cherry']

# Accessing elements

print(fruits[0])  

# Adding an element

fruits.append('date')

print(fruits)  

# Removing an element

fruits.remove('banana')

print(fruits) 

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apple

['apple', 'banana', 'cherry', 'date']

['apple', 'cherry', 'date']

Level 2: List Slicing and Iteration

# Slicing a list

print(fruits[1:3])  # Output: ['cherry', 'date']

# Iterating over a list

for fruit in fruits:

    print(fruit)

    

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['cherry', 'date']

apple

cherry

date

Level 3: List Comprehensions

List comprehensions offer a concise way to create lists. They can replace loops for generating list elements.

# Creating a list of squares using list comprehension

squares = [x**2 for x in range(10)]

print(squares)  

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[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

Level 4: Nested Lists and Multidimensional Arrays

# Creating a nested list (2D array)

matrix = [

    [1, 2, 3],

    [4, 5, 6],

    [7, 8, 9]

]

# Accessing elements in a nested list

print(matrix[1][2])  # Output: 6

# Iterating over a nested list

for row in matrix:

    for elem in row:

        print(elem, end=' ')

    print()

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6

1 2 3 

4 5 6 

7 8 9 

Level 5: Advanced List Operations

# List comprehension with conditionals

even_squares = [x**2 for x in range(10) if x % 2 == 0]

print(even_squares)  

# Using higher-order functions: map, filter, and reduce

from functools import reduce

numbers = [1, 2, 3, 4, 5]

# Map: Apply a function to all items in the list

doubled = list(map(lambda x: x * 2, numbers))

print(doubled)  #

# Filter: Filter items based on a condition

even_numbers = list(filter(lambda x: x % 2 == 0, numbers))

print(even_numbers)  

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[0, 4, 16, 36, 64]

[2, 4, 6, 8, 10]

[2, 4]

# Reduce: Reduce the list to a single value

sum_of_numbers = reduce(lambda x, y: x + y, numbers)

print(sum_of_numbers)  

# List references and copying

list1 = [1, 2, 3]

list2 = list1  # list2 is a reference to list1

list2.append(4)

print(list1)  

# Proper copying

list3 = list1.copy()

list3.append(5)

print(list1)  

print(list3)  

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15

[1, 2, 3, 4]

[1, 2, 3, 4]

[1, 2, 3, 4, 5]