How can I get raw USB keyboard data with Python?

I am using PyUSB in Python as I will have to listen an USB port to retrieve data from an electronic card. For the moment, I have to train myself by reading direct input from a small keyboard (USB-connected) connected to a Raspberry-Pi. Of course, I do not want to read the typed String, I expect to get ASCII codes for example. I just don't get how I could read input from my USB-keyboard.

I already found some snippets :

import usb.core
import usb.util

VENDOR_ID = 0x0922
PRODUCT_ID = 0x8003

# find the USB device
device = usb.core.find(idVendor=VENDOR_ID,
                       idProduct=PRODUCT_ID)

# use the first/default configuration
device.set_configuration()
# first endpoint
endpoint = device[0][(0,0)][0]

# read a data packet
attempts = 10
data = None
while data is None and attempts > 0:
    try:
        data = device.read(endpoint.bEndpointAddress,
                           endpoint.wMaxPacketSize)
    except usb.core.USBError as e:
        data = None
        if e.args == ('Operation timed out',):
            attempts -= 1
            continue

print data

Either I get the error 16 "Device is busy" or nothing at all if I uncomment the following line "device.set_configuration()" which causes the "Device is busy" exception... (I did replace VENDOR_ID and PRODUCT_ID with my keyboard's ids)

I'm assuming that you are using Linux, as you mentioned the Raspberry Pi. You can use python-evdev to read data from the event devices in /dev/input/.

For example:

from evdev import InputDevice, categorize, ecodes

device = InputDevice("/dev/input/event3") # my keyboard
for event in device.read_loop():
    if event.type == ecodes.EV_KEY:
        print(categorize(event))

Output:

key event at 1462881252.506405, 30 (KEY_A), up
key event at 1462881252.541371, 31 (KEY_S), up
key event at 1462881252.616399, 31 (KEY_S), down
key event at 1462881252.674422, 22 (KEY_U), down
key event at 1462881252.730418, 31 (KEY_S), up
key event at 1462881252.745558, 22 (KEY_U), up
key event at 1462881252.808419, 50 (KEY_M), down
key event at 1462881252.914552, 23 (KEY_I), down
key event at 1462881252.925388, 50 (KEY_M), up
key event at 1462881253.003579, 49 (KEY_N), down
key event at 1462881253.066418, 34 (KEY_G), down