python-snap7 is a pure-Python library for communicating with Siemens S7 PLCs using the classic S7 protocol. It supports S7-300 and S7-400 controllers, as well as S7-1200 and S7-1500 controllers with PUT/GET access enabled. It supports Python 3.10+ on Windows, Linux, and macOS without native dependencies.
On S7-1200 and S7-1500 controllers, python-snap7 only works when PUT/GET access is enabled in TIA Portal, and it cannot access optimized data blocks. PUT/GET is unauthenticated and disabled by default, so leaving it disabled is the more secure configuration.
If PUT/GET is disabled, or you need optimized data blocks or symbolic access, use s7commplus instead:
pip install s7commplus
s7commplus is a separate, younger project that implements S7CommPlus, the protocol these controllers speak natively. Check the firmware versions validated so far before relying on it, and see the PLC support matrix for what python-snap7 supports on each controller family.
Install from PyPI:
pip install python-snap7
from s7 import Client
client = Client()
client.connect("192.168.1.10", 0, 1)
data = client.db_read(1, 0, 4)
client.disconnect()
The s7 package is the recommended import. The snap7 package name is
also available for backwards compatibility.
Read the full documentation at python-snap7.readthedocs.io.
The safe volunteer hardware-test procedure is in Real-PLC acceptance testing.