Master Python Lists: Essential Operations and Practical Examples

List Characteristics

A mutable ordered collection that can store items of any type, including other lists.

Defined with square brackets [] and items separated by commas.

Elements are accessed by zero‑based indices and support negative indexing.

Creating Lists

Simply place comma‑separated values inside brackets:

list1 = [1, 2, 3, 4, 5]
list2 = [12, "kkk", ["12", "bb"]]

Basic List Operations

Access elements, get length, and combine lists:

# Indexing
list1[1]          # 2
list1[-1]         # 5
len(list1)         # 5
# Concatenation
list3 = list1 + list2
# Repetition
list4 = ["hello world"] * 3
# Membership test
7 in list1        # False
7 in list2        # True

Iterating Over a List

for e in list1:
    print(e)
# Output: 1 2 3 4 5

Common Built‑in Functions

max(list1)         # 5
min(list1)         # 1
list1.index(2)    # 1
sum(list1)         # 15
sum(list1)/len(list1)  # 3.0

List Methods

append(item)

– add an element to the end. count(item) – count occurrences. extend(iterable) – extend list with another iterable. pop(index) – remove and return element at index. remove(item) – remove first matching element. reverse() – reverse in place. sort() – sort in ascending order.

list1.append(15)
list1
# [1, 2, 3, 4, 5, 15]
list4 = [1,2,3,5,6,1,23,5,6,1,2,3,4,5,15]
list4.pop(1)       # 2
list4.remove(5)    # removes first 5
list4.reverse()
list4.sort()
list4
# [1, 1, 1, 2, 3, 3, 4, 5, 5, 6, 6, 15, 23]

Slicing and Advanced Indexing

# Slice (start:stop)
list4[3:6]          # [2, 3, 3]
# Slice with step
list4[3:10:2]       # [2, 3, 5]
# Reverse slice
list4[::-1]         # [23, 15, 6, 6, 5, 5, 4, 3, 3, 2, 1, 1, 1]
# Assign to slice
list4[3:6] = [22, 22, 22]
list4
# [1, 1, 1, 22, 22, 22, 4, 5, 5, 6, 6, 15, 23]

Conversion to Set

unique = set(list4)   # {1, 2, 3, 4, 5, 6, 15, 22, 23}
len(unique)          # 9

Next Steps

The next article in this series will cover Python dictionaries, a more powerful data structure for key‑value mapping.