How to Generate a UUID in Python

Python generates UUIDs with its built-in uuid module — no pip install required. uuid.uuid4() returns a random v4 UUID in one line. This guide covers every Python UUID method with copy-paste examples, string formatting options, and when to use each version.

uuid.uuid4() — The Standard Method for Random UUIDs

import uuid

# Generate a single UUID v4
new_id = uuid.uuid4()
print(new_id)
# Output: 550e8400-e29b-41d4-a716-446655440000

# As a string (most common usage)
id_str = str(uuid.uuid4())
print(id_str)
# Output: '550e8400-e29b-41d4-a716-446655440000'

# As a string without dashes
id_no_dashes = uuid.uuid4().hex
print(id_no_dashes)
# Output: '550e8400e29b41d4a716446655440000'

# Uppercase
id_upper = str(uuid.uuid4()).upper()
print(id_upper)
# Output: '550E8400-E29B-41D4-A716-446655440000'

uuid.uuid4() uses os.urandom() internally — cryptographically secure random bytes from your OS. It is the right choice for database IDs, session tokens, API keys, and any other use case where you need a unique identifier.

All Python UUID Methods — uuid1, uuid3, uuid4, uuid5

Method	Type	When to Use
uuid.uuid1()	Time + MAC address	When you need sortable UUIDs or want embedded timestamp. Leaks MAC address — avoid for public-facing IDs.
uuid.uuid3(name, namespace)	MD5 hash of input	Deterministic UUID from a string. Same input always produces the same UUID. Good for idempotent operations.
uuid.uuid4()	Random (crypto)	Default choice. Random, no embedded info, crypto-secure.
uuid.uuid5(name, namespace)	SHA-1 hash of input	Like uuid3 but uses SHA-1. Preferred over uuid3 for new code.

import uuid

# uuid3 and uuid5 — deterministic from string input
namespace = uuid.NAMESPACE_DNS

name_based_3 = uuid.uuid3(namespace, 'example.com')
print(name_based_3)
# Always: '5df41881-3aed-3515-88a7-2f4a814cf09e'

name_based_5 = uuid.uuid5(namespace, 'example.com')
print(name_based_5)
# Always: '2ed6657d-e927-568b-95e3-af9b2-6b2d39'

# Available namespaces
print(uuid.NAMESPACE_DNS)
print(uuid.NAMESPACE_URL)
print(uuid.NAMESPACE_OID)
print(uuid.NAMESPACE_X500)

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Common UUID Operations in Python

import uuid

# Generate multiple UUIDs
uuids = [str(uuid.uuid4()) for _ in range(10)]
print(uuids)

# Parse/validate a UUID string
try:
    parsed = uuid.UUID('550e8400-e29b-41d4-a716-446655440000')
    print(parsed.version)  # Output: 4
    print(parsed.hex)      # '550e8400e29b41d4a716446655440000'
    print(parsed.int)      # integer representation
except ValueError:
    print('Invalid UUID')

# Check UUID version
def get_uuid_version(uuid_str):
    try:
        return uuid.UUID(uuid_str).version
    except ValueError:
        return None

# UUID as bytes (16 bytes binary)
u = uuid.uuid4()
print(u.bytes)       # 16-byte binary
print(u.bytes_le)    # little-endian variant

UUID in Django and SQLAlchemy

Django — UUID primary key

import uuid
from django.db import models

class Order(models.Model):
    id = models.UUIDField(
        primary_key=True,
        default=uuid.uuid4,
        editable=False
    )
    # Note: default=uuid.uuid4 (not uuid.uuid4())
    # Pass the function, not the result

SQLAlchemy

from sqlalchemy import Column
from sqlalchemy.dialects.postgresql import UUID
import uuid

class Order(Base):
    __tablename__ = 'orders'
    id = Column(
        UUID(as_uuid=True),
        primary_key=True,
        default=uuid.uuid4
    )

When you just need a quick UUID to test with rather than running your full application, the WildandFree UUID Generator gives you one instantly in your browser — useful for seeding test fixtures or checking query behavior.

Performance Notes for High-Volume UUID Generation

Python's uuid.uuid4() is fast but not the fastest option if you are generating millions of UUIDs in a tight loop:

import time
import uuid

# Standard uuid4
start = time.time()
for _ in range(1_000_000):
    str(uuid.uuid4())
print(f'uuid4: {time.time() - start:.2f}s')
# Typical: ~1.5-2s on modern hardware

# Faster: generate bytes directly
import os
def fast_uuid():
    b = bytearray(os.urandom(16))
    b[6] = (b[6] & 0x0f) | 0x40  # version 4
    b[8] = (b[8] & 0x3f) | 0x80  # variant
    return '%08x-%04x-%04x-%04x-%012x' % (
        int.from_bytes(b[0:4],'big'),
        int.from_bytes(b[4:6],'big'),
        int.from_bytes(b[6:8],'big'),
        int.from_bytes(b[8:10],'big'),
        int.from_bytes(b[10:16],'big')
    )

For most applications, the standard uuid.uuid4() is fast enough. Micro-optimization is only worthwhile if UUID generation appears in profiling as a bottleneck.

Frequently Asked Questions

What is the difference between uuid.uuid4() and uuid.uuid4().hex?

uuid.uuid4() returns a UUID object. str(uuid.uuid4()) gives "550e8400-e29b-41d4-a716-446655440000" with hyphens. uuid.uuid4().hex gives "550e8400e29b41d4a716446655440000" — the same value without hyphens, as a plain hex string.

Is Python uuid.uuid4() cryptographically secure?

Yes. Python's uuid4() reads from os.urandom() which uses the operating system's cryptographically secure random number generator (/dev/urandom on Linux/Mac, CryptGenRandom on Windows). It is safe to use for session tokens, API keys, and any security-sensitive identifier.

How do I generate a UUID v7 in Python?

Python's standard library does not include uuid7 yet. Use the uuid6 package: pip install uuid6, then import uuid6; uid = uuid6.uuid7(). UUID v7 is time-ordered, which improves database index performance. See our UUID version guide for when v7 is worth the extra dependency.

How do I validate that a string is a valid UUID in Python?

Use try/except with uuid.UUID(). If the string is not a valid UUID, it raises ValueError. Example: try: uuid.UUID(my_string); except ValueError: handle_invalid(). This validates format but not version — check uuid.UUID(s).version if version matters.