Skip to main content

Python VISA bindings for GPIB, RS232, TCPIP and USB instruments

Project description


Continuous integration Documentation building Keysight assisted testing Code Coverage Documentation Status PyPI - License PyPI

A Python package for support of the “Virtual Instrument Software Architecture” (VISA), in order to control measurement devices and test equipment via GPIB, RS232, Ethernet or USB.


The programming of measurement instruments can be real pain. There are many different protocols, sent over many different interfaces and bus systems (GPIB, RS232, USB). For every programming language you want to use, you have to find libraries that support both your device and its bus system.

In order to ease this unfortunate situation, the Virtual Instrument Software Architecture (VISA) specification was defined in the middle of the 90’. Today VISA is implemented on all significant operating systems. A couple of vendors offer VISA libraries, partly with free download. These libraries work together with arbitrary peripheral devices, although they may be limited to certain interface devices, such as the vendor’s GPIB card.

The VISA specification has explicit bindings to Visual Basic, C, and G (LabVIEW’s graphical language). Python can be used to call functions from a VISA shared library (.dll, .so, .dylib) allowing to directly leverage the standard implementations. In addition, Python can be used to directly access most bus systems used by instruments which is why one can envision to implement the VISA standard directly in Python (see the PyVISA-Py project for more details). PyVISA is both a Python wrapper for VISA shared libraries but can also serve as a front-end for other VISA implementation such as PyVISA-Py.

VISA and Python

Python has a couple of features that make it very interesting for measurement controlling:

  • Python is an easy-to-learn scripting language with short development cycles.
  • It represents a high abstraction level [2], which perfectly blends with the abstraction level of measurement programs.
  • It has a very rich set of native libraries, including numerical and plotting modules for data analysis and visualisation.
  • A large set of books (in many languages) and on-line publications is available.


  • Python (tested with 3.6+)
  • VISA (tested with NI-VISA 17.5, Win7, from and Keysight-VISA )


Using pip:

$ pip install pyvisa

or easy_install:

$ easy_install pyvisa

or download and unzip the source distribution file and:

$ python install


The documentation can be read online at

PyVISA was originally programmed by Torsten Bronger and Gregor Thalhammer, Innsbruck, Austria. It is based on earlier experiences by Thalhammer.

It was maintained from March 2012 to August 2013 by Florian Bauer. It is currently maintained by Hernan E. Grecco <>.

Other contributors, listed alphabetically, are:

If you think your name should be here, please let me know.

PyVISA Changelog

1.11.3 (07-11-2020)

1.11.2 was skipped due to an issue in the MANIFEST file.

  • fix MANIFEST to exclude built docs
  • fix minor typos in deprecation warning for GPIB resources
  • generate some test files on the fly to avoid issue when building conda packages
  • add official Python 3.9 support

1.11.1 (30-09-2020)

  • deprecate methods that were mistakenly added to GPIB::INSTR resources PR #560
  • fix the listing of available backends (Also not that we now return the backend name as can be used to create a ResourceManger) PR #545
  • allow a None value for the board value of a ResourceInfo PR #547 This allows for funky resource name such ASRL/dev/tty0::INSTR which are common in pyvisa-py and avoid returning a completely generic resource in those cases.

1.11 (16-09-2020)

PyVISA 1.11 introduces a small backward incompatibility in the handling of the arguments to handlers for VISA events. The old system was tightly linked to the ctwrapper and not really usable as it was. As a consequence we pass the contents of the ctypes objects to the handler rather than the bare ctypes object (with the exception of the user handle for which there is no way to do it properly). This is a breaking change and if your code is affected you can revert to the old behavior by setting the environment variable PYVISA_WRAP_HANDLER=0 or set ctwrapper.WRAP_HANDLER to False but please consider updating to the new behavior.

PyVISA 1.11 also removes deprecated functions and attributes that were supposed to be removed in 1.10:

  • ask: use query instead
  • ask_delay: use query_delay
  • ask_for_values: use either query_ascii_values or query_binary_values as relevant
  • write_values: use either write_ascii_values or write_binary_values as relevant
  • read_values: use either read_ascii_values or read_binary_values as relevant
  • query_values: use either query_ascii_values or query_binary_values as relevant
  • values_format: has no equivalent simply pass the proper argument to either the ascii or binary variant of the function (read_xxxx_values, write_xxxx_values, query_xxxx_values)
  • Add support for “s” and “p” binary format which can be used to retrieve binary files from instruments. PR #536
  • Convert the testsuite to use pytest PR #531 This is motivated by the possibility to re-use it in PyVISA-py. However since unittest use inheritance to detect tests, doing so would have been clunky, pytest name base detection works better for that purpose.
  • Setup Azure pipelines for self-hosted runner using Keysight tools to run an extended set of tests. PR #531
  • Introduce an enumeration for special VISA timeout values PR #531
  • Provide VisaLibraryBase.handle_return_value to ease the handling of return values in alternative backends PR #525
  • Transition to using dataclasses for resource name PR #525 This is NOT fully backward compatible if you used to index the resource name
  • Allow alternative backends to use an _ instead of a - in their name PR #525
  • Add Event class to provide a nice interface to VISA events PR #511
  • Add wrap_handler to provide a nicer way to write event handler PR #511
  • Add wrapper classes for events PR #511
  • Add typing to the entire codebase PR #511
  • Use black and isort on the code to homogenize style PR #511
  • Convert docstrings to use numpy formatting PR #511
  • Explicitly set attributes on resources to make the code more readable PR #511
  • Make MessageBasedResource.read_bytes break on message end when break_on_termchar is True PR #511
  • Add support for dll_extra_paths in .pyvisarc to provide a way to specify paths in which to look for dll on Windows and Python >= 3.8 PR #509
  • Drop Python 2 support PR #486
  • Limit support to Python 3.6+ PR #486
  • Improve the test suite and introduce tests relying on Keysight Virtual instrument software PR #486
  • Add badges to the README PR #486
  • Improve ResourceManager.list_opened_resource to list only open resources. Previously all resources created and not yet garbage collected were listed. PR #486
  • Always normalize resource names PR #486
  • Treat floating points number as double when parsing ASCII data blocks PR #486
  • Allow bound methods as handler function (the use of is in tests prevented it) PR #486
  • Deprecate some unused functions found in the module PR #486
  • Warn or raise if the beginning of a binary block is not found among the first characters. The default value is 25. PR #486
  • Make the library less biased towards National Instrument by referring to IVI where relevant. In particular rename the @ni backend to @ivi PR #456
  • Deprecate the visa module that is causing issue with the VISA payment processing package PR #448

1.10.1 (2019-09-11)

  • Fix reading binary values with an empty header PR #454
  • Allow to use different headers in write_binary_values PR #454
  • Remove delay kwarg from read_ascii_values which should never have been there PR #454
  • Clarify the documentation about open_timeout PR #451

1.10 (2019-08-09)

  • Change the returned data_length for IEEE block of undefined size to 0 PR #435
  • Add chunk_size and data_length keyword argument to read/query_binary_values PR #435
  • Make the ordering of the visa library deterministic PR #399
  • Properly close pipes when looking for a shared library path on linux #380
  • Fixing missing argument for USBInstrument.usb_control_out PR #353
  • avoid attempting to close already closed resources in del PR #424
  • add a list_opened_resources method to the ResourceManager PR #415
  • use privately stored resource name in Resource class rather than relying on VisaLibrary PR #415
  • keep track of resources created by the ResourceManager to properly close them PR #357
  • replace time.clock by time.perf_counter under Python 3 PR #441
  • make the ordering of the visa library deterministic PR #399
  • properly close pipes when looking for a shared library path on linux #380
  • fixing missing argument for USBInstrument.usb_control_out PR #353
  • usb_control_out -> control_out. warnings for deprecated usb_control_out PR #353
  • Added new function log_to_stream() PR #363
  • Made all enumerations of the constants module unique. Fixed duplicate enums in StatusCode PR #371
  • Use ni backend when specifying a file in open_visa_library PR #373
  • Add flush() method to all resource classes that support viFlush() (with the exception of VXIInstrument class) PR #390

1.9.1 (2018-08-13)

  • Add expect_termination argument to read_binary_values and query_binary_values. This allows to retain the behavior of these methods from pyvisa 1.8, where the length of the block of values that is being read did not include the very final read termination. For instruments omitting the termination character when transferring binary data, visa library raises a timeout exception in case pyvisa 1.9.0 is used. Note that the behavior is not reverted completely to its pyvisa 1.8 state because for other instruments (for example, Keysight PNA on Ethernet) the termination character is indeed added at the end of the message, and is not counted in the declared length in the header. Prior to 1.9, if the last character of the binary block is also the termination character, the actual termination could be missed, which leads to hard to debug bugs hence the choice to preserve 1.9 behavior by default. PR #349
  • fix an encoding handling issue in PR #343
  • if installed use pyvisa-py backend if a binary VISA implementation is not installed. PR #341
  • make custom exception hashable by removing __eq__. This should not impact user code. PR #340
  • fix an issue with the default value for GPIB secondary address in PR #336
  • ensure docstrings exist before manipulating them ( PR #318
  • documentation improvements PR #320 #323

1.9 (2017-02-25)

  • Drop support for Python 2.6, 3.2 and 3.3 PR #300
  • add the missing read_binary_values and read_ascii_values (PR #301)
  • deprecate old methods in MessageBased (ask, read_values, query_values, write_values, ask_delay) (PR #301)
  • add support for hp headers in binary data (PR #301)
  • fix encoding issue in write_ascii_values (PR #301)
  • use import to load backend rather than pkgutil.iter_modules. This allows PyVISA to support PyInstaller PR #307
  • improvements to the visa shell: attributes type conversion (PR #299), termchar command (PR #285), timeout command (PR #284), support for non-default backend (PR #283), console script pyvisa-shell (PR #286)
  • improve speed for large data transfer by using bytearray instead of bytes (PR #282)
  • make Resource a context manager closing it. (PR #255)
  • add 64 bits version of registry based functions (PR #278)
  • make exceptions pickable (PR #249)
  • add resource_name to the output of parse_resource_extended (PR #238)
  • fix wait_on_event behavior in case of timeout (PR #234)
  • allow selecting the backend using the PYVISA_LIBRARY env var (PR #195)

1.8 (2015-08-24)

  • Fixed error reporting with Unicode filenames. (Issue #136)
  • Improved documentation.
  • Clarify timeout getter and setter. (Issue #167)
  • In open_resource, return a Resource object and warns if resource class not registered.
  • Register resource class for empty resource class.
  • Allow registering parent resource classes.
  • Changed types in wrapper to be platform independent (viStatus is always 32 bit). (Issue #134)
  • Fix a not a invalid EventType bug. (Thanks lupien)
  • Added optional resource_pyclass to open_resource.
  • Fixed bug in serial flush. (Thanks bkstein)
  • Implemented resource name parsing in pure python.

1.7 (2015-05-16)

  • Removed find_next and find_resources from VisaLibraryBase. (Issue also #135, thanks)
  • Implemented parse_resource and parse_resource_extended.
  • Created rname module to parse Resource Names.
  • Properly cleanup visa handlers upon resource close. (thanks lupien)
  • Improved gpib classes (thanks lupien)
  • Fixed bug in binary data writing. (Issue #140, thanks burnpack)
  • Fix reseting of line termination for serial. (Issue #147, thanks lupien)
  • Added property to resource name returning the InterfaceType value.
  • Added backend information to logging.
  • Added the flow_control attribute to ASRL resources. (Issue #144, thanks lupien)
  • Remove empty entry in resources caused by attribute registration. (Issue #144, thanks lupien)
  • Make container=numpy.array work consistently. (Issue #142, thanks Martin Ritter)
  • Create compact/ for python2/3 compatibility. (thanks Martin Ritter)
  • Improve install and uninstall handlers (Issue #138, #139, #151 thanks lupien)
  • Prevents cygwin segfaults. (Issue #131)
  • Better error reporting when a resource cannot be found. (Issue #129)
  • Suppress VI_SUCCESS_MAX_CNT warning on read raw. (Issue #116)
  • Implemented smarter query values based on looking how many bytes are expected. (Issue #118)
  • Fix UnicodeDecodeError on wrong file for library load (Issue #136, thanks lupien)

1.6.3 (2015-02-08)

  • Added support to Rhode and Schwartz Passport driver. (Issue #115)
  • Fixed access to the interface_type property. (Issue #114, thanks mordoror)
  • Imported constants module in visa module. (Issue #72)

1.6.2 (2014-12-29)

  • Proper handling of VI_ERROR_RSRC_NFOUND.
  • Added conditional dependency for unittest2 in Python2.6 (Issue #107)
  • Fixed Shell on Windows. (Issue #101)
  • Moved Lantz Shell to PyVISA.
  • Easier way to get debug information.
  • Better debug info for backends.

1.6.1 (2014-10-28)

  • Add ignore_warning methods to Resource and ResourceManager.
  • Added more formats to binary values. (Issue #92)
  • Fixed exception raising in legacy read_values. (Issue #91)
  • Provide a backend hook to display debug info.
  • Better debug info for binary libraries.
  • Fixed exceptions formatting (thanks Matthew94)

1.6 (2014-09-28)

  • 13 Resource Classes covering all resource types.
  • Attributes classes provided introspection to VISA attributes.
  • Many VISA attributes added to Resource Classes.
  • Use of IntEnum for common constants.
  • Better documentation.
  • Implementation of discoverable backends.
  • New functions to encode and decode of IEEE blocks.
  • New functions to encode and decode of ASCII blocks.
  • New API to transfer values from the instrument.
  • Renamed ask/ask_delay/ask_for_values to ask/query_delay/query_values. Old names still available for backwards compatibility.
  • Implemented Group Execute Trigger for GPIBInterface. (Issue #67)
  • Make setuptools a requirement. (Issue #64 and 68)
  • Simplified testing.
  • Removed legacy subpackage.
  • Removed string handling wrappers.
  • Removed Instrument class in favour of Resource.
  • Removed status and implemented thread-safe, per instrument, last_status.
  • Refactored warning ignoring mechanisms to a thread-safe one.
  • Added enum34 requirement for Python < 3.4.
  • Removed deprecated term_chars.

1.5 (2014-06-24)

  • Python 3.2+ compatibility. (Issue #32)
  • Change source encoding to utf-8.
  • Reorganized package structure. (Issue #13)
  • Improved installation.
  • Moved tests inside the package.
  • Added CI using Travis.
  • Created new wrapper for the underlying library.
  • Moved vpp43 code to legacy subpackage.
  • Moved documentation to readthedocs.
  • Make documentation mobile-friendly. (Issue #2)
  • Removed latex documentation.
  • ResourceManager is no longer a singleton. (Issue #8)
  • VisaLibrary is no longer a singleton. (Issue #7)
  • VISA functions are VisaLibrary methods. (Issue #11)
  • Improved detection of VISA library path in all OS.
  • Added diagnostics functions to help debugging.
  • Added extensive logging to help debugging. (Issue #12)
  • Improved error messages.
  • Added encoding parameter to read and write. (Issue #38)
  • Added termination parameter to read and write. (Issue #38)
  • Added size to read_raw. (Issue #37)
  • Removed delay parameter in favor of ask_delay (Issue #34)
  • Added 64 bits VISA library methods.
  • Cleaned up code.

1.4 (2012-05-13)

  • add coverage
  • add tox testing

1.3 (2008-03-26)

  • Changed licence to MIT.
  • Made determination of resource class even more careful.

1.2 (2007-09-19)

  • Changed some __getattr__ to getattr in order to have working exceptions again (e.g. timeouts) in vpp43
  • Softened the test for “INSTR” even further. Introduced the “stb” property for GPIB instruments.
  • Changed “is not an INSTR” error to a warning.
  • Added correct prefix for RPM in setup.cfg.

1.1 (2006-11-21)

  • Mentioned possible AttributeError with viParseRsrcEx.
  • Made secure against missing viParseRsrcEx.
  • Removed superfluous calls to parse_resource_extended.
  • Script can now handle installation with or without setuptools.
  • Switched to new distutils version.

1.0 (2006-01-23)

  • New properties of SerialInstrument explained.
  • Added many further properties to SerialInstrument.

0.9.7 (2005-09-21)

  • Renamed timeout parameter in open() to open_timeout.
  • Renamed Timeout parameter in open() to open_timeout.
  • Added section about SerialInstrument.
  • Added class SerialInstrument. Made termination characters even more robust.

0.9.6 (2005-08-31)

  • Renamed TypeError to VisaTypeError.
  • Added InvalidBinaryFormat. Renamed TypeError to VisaTypeError.
  • Added a lot of docstrings. Fixed bug with ValueError exception raising.
  • Eliminated string exceptions. A little bit of code clean-up.
  • Added old distutils inclusion for RPM that cause trouble with my setuptools installation.
  • Set default for term_chars to None and implemented it in write() method.
  • Described new default for term_chars.
  • Added instrument(). Fixed bugs in __repr()__.
  • Improved documentation.
  • Switched from distutils to setuptools.

0.9.5 (2005-08-27)

  • Changed package name to “PyVISA”.
  • Switched from distutils to setuptools.

0.9.4 (2005-08-12)

  • Added filename selection for VISA DLL with Windows in
  • Added code to skip over header before binary data.
  • Cleaned up whitespace.
  • Added support for endianess in case of binary transfers.
  • Improved binary reading; now it also accepts things like “#267…”.

0.9.3 (2005-07-21)

  • Changed default termination characters to “” for GPIB instruments. LF and CR are completely stripped from the end of read string, no matter how the termination characters are set.

0.9.2 (2005-07-19)

  • Added remaining keyword arguments for Instrument constructor. Added CR and LF. Added working support for reading binary data.
  • Added ask() and ask_for_values().
  • Partially implemented binary reading.
  • Split the old term_chars in term_chars, delay, and send_end.
  • Implemented warning system for invalid keyword arguments. Added test for valid float values in read_floats(). Added full term_char string in __get_term_char().
  • Standard timeout increased from 2 to 5 seconds.
  • read_floats() returns always a list.
  • Moved trigger() method to Instrument class.
  • Fixed bug in regular expression for termination characters.
  • Fixed bug with ignored term_char attribute for GPIB instruments.
  • Increased chunk_size’s default value and added it to the keyword arguments of the constructor.

0.9.1 (2005-07-03)

  • Added properties resource_name and resource_class to ResourceTemplate. Used both to simplify code.

0.9 (2005-06-29)

  • First usable release. See ChangeLog for more information.

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Files for PyVISA, version 1.11.3
Filename, size File type Python version Upload date Hashes
Filename, size PyVISA-1.11.3-py3-none-any.whl (189.3 kB) File type Wheel Python version py3 Upload date Hashes View
Filename, size PyVISA-1.11.3.tar.gz (233.4 kB) File type Source Python version None Upload date Hashes View

Supported by

AWS AWS Cloud computing Datadog Datadog Monitoring DigiCert DigiCert EV certificate Facebook / Instagram Facebook / Instagram PSF Sponsor Fastly Fastly CDN Google Google Object Storage and Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Salesforce Salesforce PSF Sponsor Sentry Sentry Error logging StatusPage StatusPage Status page