How to Merge Python Lists Efficiently Using List Comprehensions

Introduction

Hello everyone, I’m PiPi. Recently a member of a Python group asked a basic list‑processing question, so I’m sharing the solution here.

Problem Statement

The original task is to transform a left‑hand list into a merged right‑hand list as shown in the figure.

Solutions

Several answers were provided. The first solution, contributed by users “流水线” and “hclw”, is illustrated below.

Another, more complex implementation was later shared, also achieving the same result.

My original code, which also works, is shown below.

Among the many possible methods, using a list comprehension is the most Pythonic.

Conclusion

This article examined a basic Python list problem, provided detailed analysis and multiple code implementations, and highlighted the list‑comprehension technique as the preferred solution.