Programming languages

Problem:

When trying to run a Python script using PyVISA with a USB instrument, you see the following error message:

ValueError: Please install PyUSB to use this resource type.
No module named 'usb'

Solution:

On Linux distributions such as Ubuntu, you can fix this using

sudo apt-get -y install python3-usb

This will install the Python3 usb package and the libusb system packages.

In our previous post Matplotlib custom SI-prefix unit tick formatter we showed how to format a matplotlib Y axis with a custom unit with SI prefixes.

Similarly, we can use UliEngineering.Math.Decibel in order to format plots (most notably plots with a logarithmic Y axis) as decibels:

from UliEngineering.Math.Decibel import *
import matplotlib.ticker as mtick

def decibel_formatter(v0=1.0, unit='dB'):
    def format_value(value, pos=None):
        dB = value_to_dB(value, v0=v0)
        return f'{dB:.0f} {unit}'
    return format_value

# Usage example:
plt.gca().set_yscale("log") # Optional

plt.gca().yaxis.set_major_formatter(mtick.FuncFormatter(decibel_formatter()))

The following code will iterate over all IP addresses in the given network, i.e. 192.168.1.0 ... 192.168.1.254:

import ipaddress

network = ipaddress.ip_network('192.168.1.0/24')

for ip in network:
    print(ip)

The following variant will iterate over all IP addresses in this network except the broadcast IP address 192.168.1.255 and the network IP address 192.168.1.0:

import ipaddress

network = ipaddress.ip_network('192.168.1.0/24')

for ip in network:
    # Ignore e.g. 192.168.1.0 and 192.168.1.255
    if ip == network.broadcast_address or ip == network.network_address:
        continue
    print(ip)

Problem:

While trying to install a package using pip, you see the following error message:

x86_64-linux-gnu-gcc -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -g -fwrapv -O2 -fPIC -I/usr/local/include -I/usr/include -I/usr/include/python3.10 -c src/pyaudio/device_api.c -o build/temp.linux-x86_64-3.10/src/pyaudio/device_api.o
src/pyaudio/device_api.c:9:10: fatal error: portaudio.h: No such file or directory
    9 | #include "portaudio.h"
      |          ^~~~~~~~~~~~~
compilation terminated.
error: command '/usr/bin/x86_64-linux-gnu-gcc' failed with exit code 1
[end of output]

Solution:

On Ubuntu, you need to install the portaudio19-dev package:

sudo apt -y install portaudio19-dev