forgery 0.1.1

Fake data at the speed of Rust

forgery

Fake data at the speed of Rust.

A high-performance fake data generation library for Python, powered by Rust. Designed to be 50-100x faster than Faker for batch operations.

Installation

pip install forgery

From source (for development)

git clone https://github.com/williajm/forgery.git
cd forgery
pip install maturin
maturin develop --release

Quick Start

from forgery import fake

# Generate 10,000 names in one fast call
names = fake.names(10_000)

# Single values work too
email = fake.email()
name = fake.name()

# Deterministic output with seeding
fake.seed(42)
data1 = fake.names(100)
fake.seed(42)
data2 = fake.names(100)
assert data1 == data2

Features

• Batch-first design: Generate thousands of values in a single call
• 50-100x faster than Faker for batch operations
• Multi-locale support: 7 locales with locale-specific data
• Deterministic seeding: Reproducible output for testing
• Type hints: Full type stub support for IDE autocompletion
• Familiar API: Method names match Faker for easy migration

Locale Support

forgery supports 7 locales with locale-specific names, addresses, phone numbers, and more:

Locale	Language	Country
en_US	English	United States (default)
en_GB	English	United Kingdom
de_DE	German	Germany
fr_FR	French	France
es_ES	Spanish	Spain
it_IT	Italian	Italy
ja_JP	Japanese	Japan

from forgery import Faker

# Default locale is en_US
fake = Faker()
fake.names(5)  # American names

# Use a different locale
german = Faker("de_DE")
german.names(5)  # German names

japanese = Faker("ja_JP")
japanese.addresses(3)  # Japanese addresses with prefecture

Each locale provides:

• Names: First names, last names, and full names in the local language
• Addresses: Cities, regions/states, postal codes in the correct format
• Phone numbers: Country-specific formats and country codes
• Companies: Local company names and job titles
• Colors: Color names in the local language

API

Module-level functions (use default instance)

from forgery import seed, names, emails, integers, uuids

seed(42)  # Seed for reproducibility

# Batch generation (fast path)
names(1000)           # list[str] of full names
emails(1000)          # list[str] of email addresses
integers(1000, 0, 100)  # list[int] in range
uuids(1000)           # list[str] of UUIDv4

# Single values
name()                # str
email()               # str
integer(0, 100)       # int
uuid()                # str

Faker class (independent instances)

from forgery import Faker

# Each instance has its own RNG state
fake1 = Faker()
fake2 = Faker()

fake1.seed(42)
fake2.seed(99)

# Generate independently
fake1.names(100)
fake2.emails(100)

Available Generators

Names & Identity

Batch	Single	Description
names(n)	name()	Full names (first + last)
first_names(n)	first_name()	First names
last_names(n)	last_name()	Last names

Contact Information

Batch	Single	Description
emails(n)	email()	Email addresses
safe_emails(n)	safe_email()	Safe domain emails (@example.com, etc.)
free_emails(n)	free_email()	Free provider emails (@gmail.com, etc.)
phone_numbers(n)	phone_number()	Phone numbers in (XXX) XXX-XXXX format

Numbers & Identifiers

Batch	Single	Description
integers(n, min, max)	integer(min, max)	Random integers in range
floats(n, min, max)	float_(min, max)	Random floats in range (Note: float_ avoids shadowing Python's float builtin)
uuids(n)	uuid()	UUID v4 strings
md5s(n)	md5()	Random 32-char hex strings (MD5-like format, not cryptographic hashes)
sha256s(n)	sha256()	Random 64-char hex strings (SHA256-like format, not cryptographic hashes)

Dates & Times

Batch	Single	Description
dates(n, start, end)	date(start, end)	Random dates (YYYY-MM-DD)
datetimes(n, start, end)	datetime_(start, end)	Random datetimes (ISO 8601). Note: datetime_ avoids shadowing Python's datetime module
dates_of_birth(n, min_age, max_age)	date_of_birth(min_age, max_age)	Birth dates for given age range

Addresses

Batch	Single	Description
street_addresses(n)	street_address()	Street addresses (e.g., "123 Main Street")
cities(n)	city()	City names
states(n)	state()	State names
countries(n)	country()	Country names
zip_codes(n)	zip_code()	ZIP codes (5 or 9 digit)
addresses(n)	address()	Full addresses

Company & Business

Batch	Single	Description
companies(n)	company()	Company names
jobs(n)	job()	Job titles
catch_phrases(n)	catch_phrase()	Business catch phrases

Network

Batch	Single	Description
urls(n)	url()	URLs with https://
domain_names(n)	domain_name()	Domain names
ipv4s(n)	ipv4()	IPv4 addresses
ipv6s(n)	ipv6()	IPv6 addresses
mac_addresses(n)	mac_address()	MAC addresses

Finance

Batch	Single	Description
credit_cards(n)	credit_card()	Credit card numbers (valid Luhn)
credit_card_providers(n)	credit_card_provider()	Card network name (Visa, Mastercard, Amex, Discover)
credit_card_expires(n)	credit_card_expire()	Expiry date in MM/YY format
credit_card_security_codes(n)	credit_card_security_code()	CVV: 3 digits (Visa/MC/Discover) or 4 digits (Amex)
credit_card_fulls(n)	credit_card_full()	Complete card info dict (provider, number, expire, security_code, name)
ibans(n)	iban()	IBAN numbers (valid checksum)
bics(n)	bic()	BIC/SWIFT codes (8 or 11 characters)
bank_accounts(n)	bank_account()	Bank account numbers (8-17 digits)
bank_names(n)	bank_name()	Bank names (locale-specific)

Currency

Batch	Single	Description
currency_codes(n)	currency_code()	ISO 4217 currency codes (e.g., "USD", "EUR")
currency_names(n)	currency_name()	Currency names in English (e.g., "United States Dollar")
currencies(n)	currency()	(code, name) tuples
prices(n, min, max)	price(min, max)	Prices with 2 decimal places

UK Banking

Batch	Single	Description
sort_codes(n)	sort_code()	UK sort codes (XX-XX-XX format)
uk_account_numbers(n)	uk_account_number()	UK account numbers (exactly 8 digits)
transaction_amounts(n, min, max)	transaction_amount(min, max)	Transaction amounts (2 decimal places)
transactions(n, balance, start, end)	-	Full transaction records with running balance

Passwords

Batch	Single	Description
passwords(n, ...)	password(...)	Random passwords with configurable character sets

Password options:

• length: Password length (default: 12)
• uppercase: Include uppercase letters (default: True)
• lowercase: Include lowercase letters (default: True)
• digits: Include digits (default: True)
• symbols: Include symbols (default: True)

Text & Lorem Ipsum

Batch	Single	Description
sentences(n, word_count)	sentence(word_count)	Lorem ipsum sentences
paragraphs(n, sentence_count)	paragraph(sentence_count)	Lorem ipsum paragraphs
texts(n, min_chars, max_chars)	text(min_chars, max_chars)	Text blocks with length limits

Colors

Batch	Single	Description
colors(n)	color()	Color names
hex_colors(n)	hex_color()	Hex color codes (#RRGGBB)
rgb_colors(n)	rgb_color()	RGB tuples (r, g, b)

Geographic

Batch	Single	Description
latitudes(n)	latitude()	Random latitude in [-90.0, 90.0]
longitudes(n)	longitude()	Random longitude in [-180.0, 180.0]
coordinates(n)	coordinate()	(latitude, longitude) tuples

User Agents

Batch	Single	Description
user_agents(n)	user_agent()	Random browser user agent string (any browser)
chromes(n)	chrome()	Chrome user agent string
firefoxes(n)	firefox()	Firefox user agent string
safaris(n)	safari()	Safari user agent string

Booleans

Batch	Single	Description
booleans(n, probability)	boolean(probability)	Random booleans (default: 50% True)

Unique Value Generation

For batch methods that select from finite lists (names, cities, countries, etc.), you can request unique values:

from forgery import Faker

fake = Faker()
fake.seed(42)

# Generate 50 unique names (no duplicates)
unique_names = fake.names(50, unique=True)
assert len(unique_names) == len(set(unique_names))

# Generate 20 unique cities
unique_cities = fake.cities(20, unique=True)

# Generate 50 unique countries
unique_countries = fake.countries(50, unique=True)

Important Notes:

• Unique generation will raise ValueError if you request more unique values than are available in the underlying data set.
• Performance: Unique generation uses O(n) memory (stores all outputs in a HashSet) and can be O(n × 100) time in worst case due to retry logic. For very large unique batches, consider whether duplicates are actually problematic for your use case.

Financial Transaction Generation

Generate realistic bank transaction data with running balances:

from forgery import Faker

fake = Faker()
fake.seed(42)

# Generate 50 transactions from Jan to Mar 2024, starting with £1000 balance
txns = fake.transactions(50, 1000.0, "2024-01-01", "2024-03-31")

for txn in txns[:3]:
    print(f"{txn['date']} | {txn['transaction_type']:15} | {txn['amount']:>10.2f} | {txn['balance']:>10.2f}")
# 2024-01-03 | Card Payment    |    -42.50 |     957.50
# 2024-01-05 | Direct Debit    |   -125.00 |     832.50
# 2024-01-08 | Faster Payment  |   1250.00 |    2082.50

Each transaction dict contains:

• reference: 8-character alphanumeric reference
• date: Transaction date (YYYY-MM-DD)
• amount: Transaction amount (negative for debits)
• transaction_type: e.g., "Card Payment", "Direct Debit", "Salary"
• description: Merchant or payee name
• balance: Running balance after transaction

Structured Data Generation

Generate entire datasets with a single call using schema definitions:

records()

Returns a list of dictionaries:

from forgery import records, seed

seed(42)
data = records(1000, {
    "id": "uuid",
    "name": "name",
    "email": "email",
    "age": ("int", 18, 65),
    "salary": ("float", 30000.0, 150000.0),
    "hire_date": ("date", "2020-01-01", "2024-12-31"),
    "bio": ("text", 50, 200),
    "status": ("choice", ["active", "inactive", "pending"]),
})

# data[0] = {"id": "88917925-...", "name": "Austin Bell", "age": 50, ...}

records_tuples()

Returns a list of tuples (faster, values in alphabetical key order):

from forgery import records_tuples, seed

seed(42)
data = records_tuples(1000, {
    "age": ("int", 18, 65),
    "name": "name",
})
# data[0] = (50, "Ryan Grant")  # (age, name) - alphabetical order

records_arrow()

Returns a PyArrow RecordBatch for high-performance data processing:

import pyarrow as pa
from forgery import records_arrow, seed

seed(42)
batch = records_arrow(100_000, {
    "id": "uuid",
    "name": "name",
    "age": ("int", 18, 65),
    "salary": ("float", 30000.0, 150000.0),
})

# batch is a pyarrow.RecordBatch
print(batch.num_rows)     # 100000
print(batch.num_columns)  # 4
print(batch.schema)
# age: int64 not null
# id: string not null
# name: string not null
# salary: double not null

# Convert to pandas DataFrame
df = batch.to_pandas()

# Or to Polars DataFrame
import polars as pl
df_polars = pl.from_arrow(batch)

Note: Requires pyarrow to be installed: pip install pyarrow

The records_arrow() function generates data in columnar format, which is more efficient for large batches and integrates seamlessly with the Arrow ecosystem (PyArrow, Polars, pandas, DuckDB, etc.).

Schema Field Types

Type	Syntax	Example
Simple types	"type_name"	"name", "email", "uuid", "int", "float"
Integer range	("int", min, max)	("int", 18, 65)
Float range	("float", min, max)	("float", 0.0, 100.0)
Text with limits	("text", min_chars, max_chars)	("text", 50, 200)
Date range	("date", start, end)	("date", "2020-01-01", "2024-12-31")
Choice	("choice", [options])	("choice", ["a", "b", "c"])

All simple types from the generators above are supported: name, first_name, last_name, email, safe_email, free_email, phone, uuid, int, float, date, datetime, street_address, city, state, country, zip_code, address, company, job, catch_phrase, url, domain_name, ipv4, ipv6, mac_address, credit_card, iban, sentence, paragraph, text, color, hex_color, rgb_color, md5, sha256, latitude, longitude, coordinate, boolean.

Async Generation

For large datasets (millions of records), async methods prevent blocking the Python event loop:

records_async()

import asyncio
from forgery import records_async, seed

async def main():
    seed(42)
    records = await records_async(1_000_000, {
        "id": "uuid",
        "name": "name",
        "email": "email",
    })
    print(f"Generated {len(records)} records")

asyncio.run(main())

records_tuples_async()

import asyncio
from forgery import records_tuples_async, seed

async def main():
    seed(42)
    records = await records_tuples_async(1_000_000, {
        "age": ("int", 18, 65),
        "name": "name",
    })
    return records

asyncio.run(main())

records_arrow_async()

import asyncio
from forgery import records_arrow_async, seed

async def main():
    seed(42)
    batch = await records_arrow_async(1_000_000, {
        "id": "uuid",
        "name": "name",
        "salary": ("float", 30000.0, 150000.0),
    })
    return batch.to_pandas()

asyncio.run(main())

All async methods accept an optional chunk_size parameter (default: 10,000) that controls how frequently control is yielded to the event loop. Smaller chunks yield more frequently but have slightly higher overhead.

Note: Async methods use a snapshot of the RNG state at call time. The main Faker instance's RNG is not advanced, so calling the same async method twice with the same seed produces identical results. For unique results across multiple async calls, use different seeds or different Faker instances.

Arrow async chunking caveat: For records_arrow_async(), when n > chunk_size, the output differs from records_arrow() due to column-major RNG consumption within each chunk. If you need identical results to the sync version, set chunk_size >= n. The records_async() and records_tuples_async() methods always match their sync counterparts regardless of chunk size.

Custom Providers

Register your own data providers for domain-specific generation:

Basic Custom Provider

from forgery import Faker

fake = Faker()

# Register a uniform (equal probability) provider
fake.add_provider("department", ["Engineering", "Sales", "HR", "Marketing"])

# Generate values
dept = fake.generate("department")
depts = fake.generate_batch("department", 100)

Weighted Custom Provider

# Register a weighted provider (higher weights = more likely)
fake.add_weighted_provider("status", [
    ("active", 80),    # 80% probability
    ("inactive", 20),  # 20% probability
])

# Generate with weighted distribution
statuses = fake.generate_batch("status", 1000)
# Expect ~800 "active", ~200 "inactive"

Custom Providers in Records

Custom providers integrate seamlessly with records():

from forgery import Faker

fake = Faker()
fake.add_provider("department", ["Eng", "Sales", "HR"])
fake.add_weighted_provider("priority", [("high", 20), ("medium", 50), ("low", 30)])

data = fake.records(1000, {
    "id": "uuid",
    "name": "name",
    "department": "department",  # Custom provider
    "priority": "priority",      # Weighted custom provider
})

Provider Management

fake.has_provider("department")  # Check if provider exists
fake.list_providers()            # List all custom provider names
fake.remove_provider("department")  # Remove a provider

Module-level Convenience

from forgery import add_provider, generate, generate_batch, seed

seed(42)
add_provider("tier", ["gold", "silver", "bronze"])
tier = generate("tier")
tiers = generate_batch("tier", 100)

Note: Custom provider names cannot conflict with built-in types (e.g., "name", "email", "uuid").

Performance

Benchmark generating 100,000 items:

Names:
  forgery.names():  0.015s
  Faker.name():     1.523s
  Speedup: 101x

Emails:
  forgery.emails():  0.021s
  Faker.email():     2.134s
  Speedup: 101x

Benchmark generating 1,000,000 items:

Names:
  forgery.names():   0.108s
  Faker.name():     47.111s
  Speedup: 436x

Emails:
  forgery.emails():   0.167s
  Faker.email():     46.984s
  Speedup: 281x

Seeding Contract

• seed(n) affects the default fake instance only
• Each Faker instance has its own independent RNG state
• Single-threaded determinism only: Results are reproducible within one thread
• No cross-version guarantee: Output may differ between forgery versions

Thread Safety

forgery is NOT thread-safe. Each Faker instance maintains mutable RNG state.

For multi-threaded applications, create one Faker instance per thread:

from concurrent.futures import ThreadPoolExecutor
from forgery import Faker

def generate_names(seed: int) -> list[str]:
    fake = Faker()  # Create per-thread instance
    fake.seed(seed)
    return fake.names(1000)

with ThreadPoolExecutor(max_workers=4) as executor:
    results = list(executor.map(generate_names, range(4)))

Do NOT share a Faker instance across threads.

Development

# Install Rust
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

# Install maturin
pip install maturin

# Build and install locally
maturin develop --release

# Run tests
cargo test          # Rust tests
pytest              # Python tests

# Run benchmarks
python tests/benchmarks/bench_vs_faker.py

License

MIT