tgoop.com/DataScience4/8545
Create:
Last Update:
Last Update:
💡 Python Lists Cheatsheet: Essential Operations
This lesson provides a quick reference for common Python list operations. Lists are ordered, mutable collections of items, and mastering their use is fundamental for Python programming. This cheatsheet covers creation, access, modification, and utility methods.
# 1. List Creation
my_list = [1, "hello", 3.14, True]
empty_list = []
numbers = list(range(5)) # [0, 1, 2, 3, 4]
# 2. Accessing Elements (Indexing & Slicing)
first_element = my_list[0] # 1
last_element = my_list[-1] # True
sub_list = my_list[1:3] # ["hello", 3.14]
copy_all = my_list[:] # [1, "hello", 3.14, True]
# 3. Modifying Elements
my_list[1] = "world" # my_list is now [1, "world", 3.14, True]
# 4. Adding Elements
my_list.append(False) # [1, "world", 3.14, True, False]
my_list.insert(1, "new item") # [1, "new item", "world", 3.14, True, False]
another_list = [5, 6]
my_list.extend(another_list) # [1, "new item", "world", 3.14, True, False, 5, 6]
# 5. Removing Elements
removed_value = my_list.pop() # Removes and returns last item (6)
removed_at_index = my_list.pop(1) # Removes and returns "new item"
my_list.remove("world") # Removes the first occurrence of "world"
del my_list[0] # Deletes item at index 0 (1)
my_list.clear() # Removes all items, list becomes []
# Re-create for other examples
numbers = [3, 1, 4, 1, 5, 9, 2]
# 6. List Information
list_length = len(numbers) # 7
count_ones = numbers.count(1) # 2
index_of_five = numbers.index(5) # 4 (first occurrence)
is_present = 9 in numbers # True
is_not_present = 10 not in numbers # True
# 7. Sorting
numbers_sorted_asc = sorted(numbers) # Returns new list: [1, 1, 2, 3, 4, 5, 9]
numbers.sort(reverse=True) # Sorts in-place: [9, 5, 4, 3, 2, 1, 1]
# 8. Reversing
numbers.reverse() # Reverses in-place: [1, 1, 2, 3, 4, 5, 9]
# 9. Iteration
for item in numbers:
# print(item)
pass # Placeholder for loop body
# 10. List Comprehensions (Concise creation/transformation)
squares = [x**2 for x in range(5)] # [0, 1, 4, 9, 16]
even_numbers = [x for x in numbers if x % 2 == 0] # [2, 4]
Code explanation: This script demonstrates fundamental list operations in Python. It covers creating lists, accessing elements using indexing and slicing, modifying existing elements, adding new items with
append(), insert(), and extend(), and removing items using pop(), remove(), del, and clear(). It also shows how to get list information like length (len()), item counts (count()), and indices (index()), check for item existence (in), sort (sort(), sorted()), reverse (reverse()), and iterate through lists. Finally, it illustrates list comprehensions for concise list generation and filtering.#Python #Lists #DataStructures #Programming #Cheatsheet
━━━━━━━━━━━━━━━
By: @DataScience4