Original code copyright (C) 2009-2022 Rudolf Cardinal (

This file is part of cardinal_pythonlib.

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Random number generation.

cardinal_pythonlib.randomness.coin(p: float) → bool[source]

Flips a biased coin; returns True or False, with the specified probability being that of True.

cardinal_pythonlib.randomness.create_base64encoded_randomness(num_bytes: int) → str[source]

Create and return num_bytes of random data.

The result is encoded in a string with URL-safe base64 encoding.

Used (for example) to generate session tokens.

Which generator to use? See

Do NOT use these methods:

randbytes = M2Crypto.m2.rand_bytes(num_bytes) # NO!
randbytes = Crypto.Random.get_random_bytes(num_bytes) # NO!

Instead, do this:

randbytes = os.urandom(num_bytes)  # YES
cardinal_pythonlib.randomness.generate_random_string(length: int, characters: str = None) → str[source]

Generates a random string of the specified length.


random() -> x in the interval [0, 1).