Random application IDs
Create opaque identifiers for records, requests, or resources without coordinating a central counter.
Python · Module
uuid
Python’s uuid module provides immutable UUID objects and functions for generating UUIDs across RFC 9562 versions. It supports parsing and constructing UUIDs from text, bytes, fields, or integers.
How it works
The module supplies immutable UUID objects and factory functions for several RFC 9562 UUID versions. Use uuid4() for a random identifier, or construct UUID values from supported representations such as text, bytes, fields, or an integer.
Syntax
class uuid.UUID(hex=None, bytes=None, bytes_le=None, fields=None, int=None, version=None, *, is_safe=<SafeUUID.unknown>)Parameters
| Name | Type | Description |
|---|---|---|
hex / bytes / bytes_le / fields / int | str | bytes | tuple[int, ...] | int | A UUID value supplied as hexadecimal text, bytes, little-endian bytes, fields, or a 128-bit integer; the constructor also accepts version and related optional arguments documented on the page. |
Returns
UUID objects from the UUID class and UUID values from the module’s version-specific factory functions.
Key points
- The module’s UUID class represents values that cannot be altered after construction.
- Factory functions create UUIDs according to particular RFC 9562 versions.
- uuid3() belongs to the module’s version-specific generation functions.
- The UUID constructor accepts a hexadecimal string representation.
- The constructor can consume a 16-byte big-endian bytes value.
Example: Generate and inspect a random UUID
import uuid
request_id = uuid.uuid4()
print(request_id)
print(request_id.hex)Creates a random UUID and prints its canonical text form plus its 32-character hexadecimal form.
When to use it
Deterministic names
Derive a repeatable identifier from a stable namespace and name.
Representation conversion
Parse or serialize identifiers at API and storage boundaries.
Interview questions
QWhen would you choose uuid4()?
uuid4() generates a random UUID using a cryptographically secure method. It is the usual choice for opaque application identifiers when no deterministic relationship to a namespace and name is needed.
Follow-up: How would you create the same identifier repeatedly from a namespace and name? Use uuid5(namespace, name), which derives the UUID from a SHA-1 name hash.
QWhat does the UUID class represent?
UUID values are immutable objects. They can be created from a hexadecimal string, big-endian or little-endian bytes, fields, or a 128-bit integer, and expose representations such as str, bytes, and int.
Follow-up: What is the difference between bytes and bytes_le? bytes uses big-endian order, while bytes_le interprets the UUID fields in little-endian order.
QHow do name-based UUID functions differ from uuid4()?
uuid3() and uuid5() generate name-based UUIDs from a namespace UUID and a name. uuid3() uses MD5, while uuid5() uses SHA-1; the same inputs produce the same UUID.
Follow-up: Which is generally preferable for new name-based identifiers? uuid5(), because the documentation presents it as the SHA-1 variant and MD5 is an older hash choice.
Related
UUIDuuid1uuid3uuid4uuid5uuid6uuid7uuid8