How do you concatenate two lists in Python?

Concatenating Lists in Python using the + Operator

In Python, one of the most straightforward ways to merge two lists together, that is to concatenate them, is using the + operator. The + operator is Python's built-in solution for concatenation of lists.

Practical Example

For instance, consider the below example:

# Define two lists
list1 = ['a', 'b', 'c']
list2 = [1, 2, 3]

# Concatenate the lists
merged_list = list1 + list2

print(merged_list)

When you run this code, the output will be:

['a', 'b', 'c', 1, 2, 3]

Both lists list1 and list2 are merged into merged_list, preserving the order of elements from both lists.

Additional Insights and Best Practices

While using the + operator for concatenating two lists, keep in mind that it creates a new list, leaving the original lists unchanged. If you want to extend a list in-place, you may consider other options like the extend() method in Python.

Here's how to use it:

# Define two lists
list1 = ['a', 'b', 'c']
list2 = [1, 2, 3]

# Use extend() method
list1.extend(list2)

print(list1)

The extend() method modifies list1 directly and doesn't create a new list. You may choose to use the + operator or the extend() method depending on whether you need the original lists to remain unchanged or not.

Remember that, while other answers like using the * operator, the append() method, or the concat() method might look plausible, they either do not achieve the same result or do not exist as built-in Python methods for list concatenation.

In conclusion, using the + operator is the correct and the most intuitive way to concatenate two lists in Python. It's a powerful tool you can utilize to enhance the flexibility of your Python code.