Pcapy is a Python extension module that enables software written in Python
to access the routines from the pcap packet capture library.

From libpcap's documentation: Libpcap is a system-independent interface for
user-level packet capture. Libpcap provides a portable framework for
low-level network monitoring. Applications include network statistics
collection, security monitoring, network debugging, etc.

Pcapy is most useful when used together with a packet handling package such
as Impacket, a collection of Python classes for contructing and dissecting
network packets.