LPUSH

Syntax

LPUSH key value [value ...]

Description

The LPUSH command inserts one or more values at the head (left side) of a list. If the key does not exist, it is created as an empty list before performing the operation. If the key exists but is not a list, an error is returned.

Arguments

• key (required): The name of the list key.
• value (required, one or more): The value(s) to prepend to the list.

Return Value

Returns an Integer: The length of the list after the push operation.

Examples

Pushing a Single Value

LPUSH mylist "item1"

Response:

(integer) 1

Pushing Multiple Values

LPUSH mylist "item3" "item2" "item1"

Response:

(integer) 3

Note: The values are pushed in the order specified, so item1 will be at the head of the list.

Viewing the List

LPUSH mylist "c" "b" "a"
LRANGE mylist 0 -1

Response:

(integer) 3
1) "a"
2) "b"
3) "c"

Creating a New List

LPUSH newlist "first"
LRANGE newlist 0 -1

Response:

(integer) 1
1) "first"

Notes

• If the key doesn't exist, it is created as an empty list
• Values are inserted at the head (left side) of the list
• Multiple values are inserted in the order they are specified
• Returns a WRONGTYPE error if the key exists but is not a list
• The operation is atomic

Use Cases

• Stacks: Implement LIFO (Last In, First Out) data structures
• Recent Items: Add items to the front of a recent items list
• Message Queues: Add messages to the front of a queue
• Task Lists: Add tasks to the beginning of a task list

Related Commands

• RPUSH - Append values to a list
• LPOP - Remove and return values from the left
• LRANGE - Get a range of elements from a list
• LLEN - Get the length of a list