Join Lists
2 min read ·
Joining lists means combining two or more lists into one.
Python provides multiple ways to join lists, and each method behaves differently.
Choosing the right method is important for performance, readability, and correctness.
Join Lists Using + Operator
The
+ operator creates a new list by concatenating lists.Original lists remain unchanged.
Join Lists Using extend()
The
extend() method adds elements of one list to another list.list2 remains unchanged.Join Lists Using append() (Nested Result)
Using
append() adds the entire list as a single element.This creates a nested list.
Join Lists Using Loop
Useful when you need custom logic while joining.
Join Lists Using List Comprehension
Join Lists Using itertools.chain()
This method is memory-efficient for large lists.
Join More Than Two Lists
Join Lists with Different Data Types
Common Mistakes
Expecting extend() to Return a List
extend() returns None.Using append() Instead of extend()
Creates nested list unintentionally.
Performance Comparison
extend()is faster than+for large lists+creates a new listappend()should not be used for joining lists