add appendleft term

content/python/concepts/deque/terms/appendleft/appendleft.md

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+---
+Title: 'appendleft()'
+Description: 'Adds an element to the left end (front) of the deque.'
+Subjects:
+  - 'Computer Science'
+  - 'Data Science'
+Tags:
+  - 'Collections'
+  - 'Data Structures'
+  - 'Deques'
+  - 'Methods'
+  - 'Python'
+CatalogContent:
+  - 'learn-python-3'
+  - 'paths/computer-science'
+---
+
+The **`appendleft()`** method adds an element to the left end (front) of a `collections.deque` object. This is useful for managing elements in a queue-like structure, where items are added and removed from opposite ends.
+
+## Syntax
+
+```pseudo
+deque.appendleft(element)
+```
+
+**Parameters:**
+
+- `element`: The item to add to the left end (front) of the deque.
+
+**Return value:**
+
+- `None`. The deque is modified in place.
+
+## Example: Adding elements to the left side of a deque using `appendleft()`
+
+In this example, `appendleft()` adds elements to the left end of a deque, demonstrating how items are prepended to the front:
+
+```py
+from collections import deque
+
+# Create a deque
+my_deque = deque([1, 2, 3])
+print(f"Initial deque: {my_deque}")
+
+# Append an element to the left
+my_deque.appendleft(0)
+print(f"Deque after appendleft(0): {my_deque}")
+
+# Append another element
+my_deque.appendleft(-1)
+print(f"Deque after appendleft(-1): {my_deque}")
+```
+
+The output of this code is:
+
+```shell
+Initial deque: deque([1, 2, 3])
+Deque after appendleft(0): deque([0, 1, 2, 3])
+Deque after appendleft(-1): deque([-1, 0, 1, 2, 3])
+```
+
+## Codebyte Example: Using `appendleft()` for Dynamic Queue Operations
+
+In this example, `appendleft()` is used to add elements to the front of a deque, simulating dynamic queue operations where new items arrive at the front:
+
+```codebyte/python
+from collections import deque
+
+# Initialize a deque with numbers
+numbers = deque([10, 20, 30])
+print("Original deque:", numbers)
+
+# Add elements dynamically to the left
+numbers.appendleft(5)
+numbers.appendleft(0)
+
+print("Deque after dynamic prepend operations:", numbers)
+
+# Access elements to verify positions
+print("First element:", numbers[0])
+print("Second element:", numbers[1])
+print("Last element:", numbers[-1])
+```