What does it do?
pyOpenSSL gives Python programs a way to use OpenSSL, the software library responsible for securing an enormous portion of internet traffic, to create secure network connections, manage digital certificates, and handle encryption. It functions as a bridge, or an adapter plug: OpenSSL itself is written in a different programming language, and pyOpenSSL lets Python code speak to it directly rather than reinventing that same complex machinery from scratch. It’s commonly used to work with SSL certificates, the credentials that let a website prove its identity and enable the padlock icon in a browser. Because it’s a fairly direct wrapper, it exposes a lot of OpenSSL’s power, and its complexity, directly to Python code.
See it in action
This loads a website security certificate file from disk and prints out who that certificate says it was issued to.
from OpenSSL import crypto
with open("path/to/certificate.pem", "rb") as f:
cert_data = f.read()
cert = crypto.load_certificate(crypto.FILETYPE_PEM, cert_data)
print(cert.get_subject())Why would a non-developer care?
OpenSSL is one of the most important pieces of security infrastructure on the internet, and this library is how a huge amount of Python software plugs into it rather than trying to reimplement encryption from first principles, a task best left to specialists. When OpenSSL has a major security flaw, as it famously has, it ripples through everything built on top of it.
Real-world examples
OpenSSL secures a huge share of websites and servers worldwide, and its 2014 Heartbleed vulnerability became one of the most widely reported security bugs in internet history, a reminder of how much critical infrastructure quietly depends on it. pyOpenSSL has historically been used by major Python networking projects to add proper SSL and certificate support.
Who uses it
Developers and security engineers building networking software in Python that needs direct, low-level control over SSL and TLS certificates.
How it compares to alternatives
Python’s standard library includes its own built-in ssl module, which has become good enough for most common needs, but pyOpenSSL still offers more complete access to OpenSSL’s certificate-handling features for projects that need it, like Twisted has relied on historically.