How Do Python\'s `append()` and ` =` Operators Differ When Used on Lists?

Understanding Differences Between Python Append() and = Operator on Lists

The append() method and the = operator behave differently when operating on lists. append() adds the given element to the end of the list, while = concatenates the elements of the operand list to the existing list.

Consequences of Using =

Using = with a list as an operand results in a new list that combines the original list with the operand list's elements. For example:

<code class="python">c = [1, 2, 3]
c += c
print(c)  # [1, 2, 3, 1, 2, 3]</code>

Recursion with append()

In contrast, append() appends the list itself as a single element, which leads to infinite recursion if the list is added to itself. This occurs because the list's last element, accessed through c[-1], now refers to the list itself, creating a recursive loop.

<code class="python">c = [1, 2, 3]
c.append(c)
print(c)  # [1, 2, 3, [...]]  # infinite recursion</code>

Alternative Option: extend()

To append the elements of one list to another, use the extend() method. It modifies the original list in-place, unlike = which creates a new list:

<code class="python">c = [1, 2, 3]
c.extend(c)
print(c)  # [1, 2, 3, 1, 2, 3]</code>

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