Frequently asked questions¶
Is PyVISA endorsed by National Instruments?¶
No. PyVISA is developed independently of National Instrument as a wrapper for the VISA library.
Who makes PyVISA?¶
PyVISA was originally programmed by Torsten Bronger and Gregor Thalhammer. 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 <firstname.lastname@example.org>.
Take a look at AUTHORS for more information
Is PyVISA thread-safe?¶
Yes, PyVISA is thread safe starting from version 1.6.
I have an error in my program and I am having trouble to fix it¶
PyVISA provides useful logs of all operations. Add the following commands to your program and run it again:
import visa visa.log_to_screen()
I found a bug, how can I report it?¶
Please report it on the Issue Tracker, including operating system, python version and library version. In addition you might add supporting information by pasting the output of this command:
python -m visa info
Error: Image not found¶
This error occurs when you have provided an invalid path for the VISA library. Check that the path provided to the constructor or in the configuration file
Error: Could not found VISA library¶
This error occurs when you have not provided a path for the VISA library and PyVISA is not able to find it for you. You can solve it by providing the library path to the VisaLibrary or ResourceManager constructor:
>>> visalib = VisaLibrary('/path/to/library')
>>> rm = ResourceManager('Path to library')
or creating a configuration file as described in Configuring the NI backend.
Error: No matching architecture¶
This error occurs when you the Python architecture does not match the VISA architecture.
PyVISA tries to parse the error from the underlying foreign function library to provide a more useful error message. If it does not succeed, it shows the original one.
In Mac OS X the original error message looks like this:
OSError: dlopen(/Library/Frameworks/visa.framework/visa, 6): no suitable image found. Did find: /Library/Frameworks/visa.framework/visa: no matching architecture in universal wrapper /Library/Frameworks/visa.framework/visa: no matching architecture in universal wrapper
In Linux the original error message looks like this:
OSError: Could not open VISA library: Error while accessing /usr/local/vxipnp/linux/bin/libvisa.so.7:/usr/local/vxipnp/linux/bin/libvisa.so.7: wrong ELF class: ELFCLASS32
First, determine the details of your installation with the help of the following debug command:
python -m visa info
You will see the ‘bitness’ of the Python interpreter and at the end you will see the list of VISA libraries that PyVISA was able to find.
The solution is to:
Install and use a VISA library matching your Python ‘bitness’
Download and install it from National Instruments’s VISA. Run the debug command again to see if the new library was found by PyVISA. If not, create a configuration file as described in Configuring the NI backend.
If there is no VISA library with the correct bitness available, try solution 2.
Install and use a Python matching your VISA library ‘bitness’
In Windows and Linux: Download and install Python with the matching bitness. Run your script again using the new Python
In Mac OS X, Python is usually delivered as universal binary (32 and 64 bits).
You can run it in 32 bit by running:arch -i386 python myscript.py
or in 64 bits by running:arch -x86_64 python myscript.py
You can create an alias by adding the following line
alias python32=”arch -i386 python”
into your .bashrc or .profile or ~/.bash_profile (or whatever file depending on which shell you are using.)
You can also create a virtual environment for this.