How to Generate a UUID in Python

Random UUIDs With uuid4()

import uuid

u = uuid.uuid4()
print(u)        # 1b4e28ba-2fa1-4d2b-883f-0016d3cca427
print(type(u))  # <class 'uuid.UUID'>

uuid4() returns a UUID object, not a string. It's built from os.urandom(), a cryptographically secure source, with the version and variant bits set for version 4. What is UUID v4 explains the structure.

Converting Between Representations

u.bytes_le gives the little-endian byte order used by Microsoft GUIDs, useful when exchanging binary values with .NET or SQL Server.

Parsing a UUID String

import uuid

def parse_uuid(text: str) -> uuid.UUID | None:
    try:
        return uuid.UUID(text)
    except ValueError:
        return None

parse_uuid('{1B4E28BA-2FA1-4D2B-883F-0016D3CCA427}')  # accepts braces and uppercase
parse_uuid('1b4e28ba2fa14d2b883f0016d3cca427')        # accepts no hyphens

uuid.UUID() is lenient about braces, the urn:uuid: prefix, hyphens and case. If you need to enforce one exact format, compare str(parsed) with the input, or use a regex. How to validate a UUID covers both approaches.

Time-Ordered UUIDs With uuid7() (Python 3.14+)

import uuid

u7 = uuid.uuid7()
print(u7.version)  # 7

Version 7 UUIDs begin with a Unix timestamp in milliseconds, so they sort roughly by creation time, which is friendlier to database indexes. Python 3.14 also added uuid6(), uuid8() and the uuid.NIL and uuid.MAX constants. On older Python versions, use a third-party package for v7. How to generate UUID v7 compares options across languages.

Deterministic UUIDs With uuid5()

import uuid

uuid.uuid5(uuid.NAMESPACE_DNS, 'example.com')
# always the same value for the same namespace and name

uuid.uuid5(uuid.NAMESPACE_URL, 'https://example.com/products/42')

Name-based UUIDs are useful when the same input must always map to the same ID, such as deduplicating URLs or generating stable IDs from natural keys. uuid3() does the same with MD5; v5 (SHA-1) is generally preferred. UUID v3 vs v5 explains the difference.

Avoid uuid1() for New Code

uuid.uuid1() includes a timestamp and, by default, a node value derived from the machine's network hardware address when available. That can leak information about where and when an ID was made. Prefer uuid4() or uuid7() unless you need v1 for compatibility.

Using UUIDs in Frameworks

• Django: models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False). Pass the function, not uuid.uuid4(), or every row gets the same value.
• SQLAlchemy: use the Uuid type with default=uuid.uuid4.
• Pydantic: annotate fields as uuid.UUID for automatic validation.
• JSON: convert to str(u) before serialising; the standard json module doesn't handle UUID objects.

The Django note is worth repeating: passing default=uuid.uuid4() evaluates once at import time, which is a classic source of duplicate IDs.

Generating UUIDs Without Code

For quick test data, the UUID v4 generator creates up to 1,000 UUIDs in your browser and can format them with quotes for pasting into a Python list. To inspect a UUID you've been given, the UUID decoder shows its version, variant and, for time-based versions, the embedded timestamp.

Common Mistakes

• Comparing strings to UUID objects. uuid.uuid4() == '1b4e...' is always False. Convert one side: str(u) == text or u == uuid.UUID(text).
• Storing as text in PostgreSQL when a native uuid column is available. Drivers such as psycopg handle uuid.UUID values directly.
• Assuming ordering. uuid4() values have no meaningful order; use uuid7() or a timestamp column for chronology.
• Using UUIDs as secrets. For tokens, use secrets.token_urlsafe() instead.

Generating Many UUIDs

import uuid
ids = [str(uuid.uuid4()) for _ in range(1000)]

Generation is fast; a thousand UUIDs take a negligible amount of time. For writing them to a file:

from pathlib import Path
Path('ids.txt').write_text('\n'.join(ids))

Command-Line One-Liners

Python 3.12 added a command-line interface to the uuid module:

python -m uuid            # prints a random UUID (v4 by default)
python -m uuid -u uuid5 -n @dns -N example.com

Handy for shell scripts when you don't want to write a file.

Summary

uuid.uuid4() for random IDs, uuid.uuid7() on 3.14+ for time-ordered ones, uuid.uuid5() for deterministic ones. Convert with str, .hex, .bytes or .int, and pass functions, not values, as defaults.