Mypyc Runtime Library

Common errors

Warnings

Install compatibility stale last tested: 2026-05-12

Imports

• librt

  This library is primarily an internal runtime dependency for mypyc-compiled code and recent versions of mypy. Direct import of its internal symbols by end-user applications is generally not intended.

  librt provides C implementations used by mypyc-generated extensions. While Python might theoretically allow importing internal parts (e.g., `librt.internal`), this is not part of its public API and can lead to unexpected issues or breaking changes. For example, `mypy` itself uses `librt` for cache serialization and deserialization, often through internal mechanisms rather than direct `import librt` in user code.

Quickstart verified last tested: 2026-04-23

librt is a runtime library for code compiled with `mypyc`. Therefore, its 'quickstart' involves demonstrating how to use `mypyc` to compile Python code. The compiled code will then depend on `librt` at runtime. The example shows a simple Python function that `mypyc` could compile, implicitly leveraging `librt`'s optimizations.

# librt is implicitly used by mypyc-compiled modules.
# A typical quickstart involves using mypyc, which then utilizes librt.
# First, ensure librt (and mypy, which includes mypyc) are installed.
# pip install mypy mypyc

# example_module.py
# This module will be compiled by mypyc, which relies on librt at runtime.

def factorial(n: int) -> int:
    result = 1
    for i in range(1, n + 1):
        result *= i
    return result

if __name__ == '__main__':
    # In a real scenario, this would be compiled and imported as a C extension.
    # For illustration, let's just run it as normal Python.
    # To compile: mypyc example_module.py
    # This creates a C extension (e.g., example_module.cpython-XYZ.so) that depends on librt.
    print(f'Factorial of 5: {factorial(5)}')