(python) pyusb can get the idVendor, idProduct but dev is none

Question

I'm facing that for python pyusb can get the idVendor, idProduct successfully but my dev is still none, which will affect my later operation, I need a hand for here, thanks.

mostly the pyusb read and write function is working, so I am worndering.

the code

import time
from usb.core import find
from usb.util import get_string
import usb.backend.libusb1
import re
import usb.core
import usb.util
import os
import numpy as np

def info_usb_device(dev):
    xdev = find(idVendor=dev.idVendor, idProduct=dev.idProduct)
    if xdev.bDeviceClass == 9: 
        return
    if xdev._manufacturer is None:
        xdev._manufacturer = get_string(xdev, xdev.iManufacturer, langid=1033)
    if xdev._product is None:
        xdev._product = get_string(xdev, xdev.iProduct, langid=1033)
    device_info = '[%20s] %8d %9d %s - %s' % (xdev.serial_number, dev.idVendor, dev.idProduct,
                                 str(xdev._manufacturer).strip(),
                                 str(xdev._product).strip())
    return xdev.serial_number, device_info 


def add_usb_devices(device_dict):
    new_devices = []
    for bus in usb.busses():
        for dev in bus.devices:
            if dev is None:
                continue
            serial_info = info_usb_device(dev)
            if serial_info is not None:
                (serial, info) = serial_info
                if serial not in device_dict:
                    new_devices.append(serial)
                    device_dict[serial] = info
    return new_devices


if __name__ == "__main__":
    device_dict = {}
    print('%22s %8s %9s %s' % ('serial', 'idVendor', 'idProduct', 'Manufacturer - Product'))
    print('-'*22, '-'*8,  '-'*9, '-'*30)
    # first scan
    add_usb_devices(device_dict)
    for device_info in device_dict.values():
        print(device_info)
    # next scans
    for i in range(5):  # run 5 more scans 
        new_serials = add_usb_devices(device_dict)
        if len(new_serials) > 0:
           print('** (scan %d) FOUND NEW USB DEVICES/SERIALS: %s' % (i, new_serials))
           for serial in new_serials:
               print(device_dict[serial])
        time.sleep(3)  # waiting 3 seconds before new scan

    str_device_dict_serial = device_dict[serial]
    listed__device_dict_serial = re.findall(r'\b\d+\b', str_device_dict_serial)


    print('Scans completed.')

    print("+ + + + + + + + + + + + +")
    print(device_dict[serial])
    print(listed__device_dict_serial)



input_idVendor = listed__device_dict_serial[0]
input_idProduct = listed__device_dict_serial[1]

dev = usb.core.find(idVendor= input_idVendor, idProduct=input_idProduct)



print(input_idVendor)
print(input_idProduct)

print(dev)
#print(ep)

and the output:

(base) joy@joy-System-Product-Name:~$ sudo python '/home/joy/fe_dir/combined_function.py'
                serial idVendor idProduct Manufacturer - Product
---------------------- -------- --------- ------------------------------
[                None]     1133     49271 Logitech - USB Optical Mouse
[             2004888]     1423     37728  - USB Reader
[5334354E373539325A315A4B]     5117      2112 Generic - External
** (scan 2) FOUND NEW USB DEVICES/SERIALS: ['01DZTW5EXY5TSUF8']
[    01DZTW5EXY5TSUF8]    34148      4096 JetFlash - Mass Storage Device
Scans completed.
+ + + + + + + + + + + + +
[    01DZTW5EXY5TSUF8]    34148      4096 JetFlash - Mass Storage Device
['34148', '4096']
34148
4096
None

the bottom's "None" showing that somehow I couldn't get the dev

Answer 1

See example in PyUSB docs

Please read the docs. The find function requires numerical arguments for parameters idVendor and idProduct, not strings.

See example in docs

# find our device
dev = usb.core.find(idVendor=0xfffe, idProduct=0x0001)

Fix by conversion to number

The numbers can be either specified in hexadecimal format like 0x0001 or in decimal 1.

Here, your regex-search returns strings. So you need to convert those strings to numbers, e.g. using int(str):

device_formatted_str = device_dict[serial]
(idVendor, idProduct, *_) = re.findall(r'\b\d+\b', device_formatted_str)  # unpack tuple into 2 required arguments. Remainder neglected.
print(type(idVendor), idVendor, type(idProduct), idProduct)  # debug print types and values
dev = usb.core.find(idVendor=int(idVendor), idProduct=int(idProduct))  # convert string to number, here int
print(dev)

See also:

• Tutorial on unpacking: Python - Unpack Tuples