p4p

library4.2.2pypypi✓ verified 79d ago

Python interface to PVAccess (PV Access) protocol client for EPICS. Current version 4.2.2, supports Python >=2.7. Maintained by EPICS community, follow EPICS release cadence.

data communication

pip install p4p

package ↗homepage ↗

INSTALL

IMPORT

SIG · P4P

p4p

datapythonv4.2.2

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

Type

✓ from p4p import Type

✗ from p4p.client import pva

Value

✓ from p4p import Value

set_debug

✓ from p4p import set_debug

Create a PVA client context, fetch a value or monitor a PV.

import os from p4p.client.pva import Context with Context('pva') as ctx: value = ctx.get(os.environ.get('PV_NAME', 'blah:example')) print(value) # Alternatively, using channel for monitoring: with Context('pva') as ctx: ch = ctx.monitor(os.environ.get('PV_NAME', 'blah:example')) for update in ch: print(update) break # just one sample

Debug

Known issues

breakingp4p 4.0 removed support for Python 2.7. Users on older systems must pin to p4p<4.0.

fix

Use Python 3.6+ or pin to p4p==3.x.

affects: >=4.0.0

breakingContext usage changed: old import path `from p4p import Context` no longer works; use `from p4p.client import Context`.

fix

Update imports to `from p4p.client import Context`.

affects: >=4.0.0

deprecatedThe `rpc` module (p4p.client.rpc) is deprecated in favor of new `p4p.client.pva` for all operations. Expect removal in a future major release.

fix

Migrate from `from p4p.client import rpc` to `from p4p.client.pva import Context`.

affects: >=4.1.0

gotchaMany examples use `Context('pva', ...)` but the provider string is environment-specific. Default provider 'pva' works for most sites, but if server uses 'ca' or custom, must specify correctly.

fix

Check site's PV Access provider setting (e.g., EPICS_PVA_PROVIDER). Use `Context('pva')` for native PVA, or `Context('ca')` for Channel Access relay.

affects: all

gotchaMonitoring channels using `ctx.monitor()` returns an iterator that blocks indefinitely. For GUI or non-blocking applications, use `ch = ctx.monitor(...); ch.start()` with callbacks (see docs for `start` method).

fix

Use callback-based monitoring: `ch = ctx.monitor(...); ch.start(lambda x: print(x))`

affects: all

Upgrade

Version history

4.2.2latest on PyPI · released Jan 8, 2026

Audit

Dependencies

numpyrequiredRequired for numeric channel data handling.

psutiloptionalUsed for process monitoring and resource management.

Agent activity

11 hits · last 30 days

node

OpenAI (training)

Resources

packagehttps://pypi.org/project/p4p/ ↗

homepagehttps://epics-base.github.io/p4p ↗