About python keyboard interrupt

Question

I was still learning basic python programming, and was checking this program from Adafruit. And I was confused about how I am able to interrupt/stop the program by clicking CTRL + C, but in this file I don't see any "KeyboardInterrupt" function etc. It's just a string of comment from the author. Here is the code :


# Simple example of reading the MCP3008 analog input channels and printing
# them all out.
# Author: Tony DiCola
# License: Public Domain
import time

# Import SPI library (for hardware SPI) and MCP3008 library.
import Adafruit_GPIO.SPI as SPI
import Adafruit_MCP3008


# Software SPI configuration:
# CLK  = 18
# MISO = 23
# MOSI = 24
# CS   = 25
# mcp = Adafruit_MCP3008.MCP3008(clk=CLK, cs=CS, miso=MISO, mosi=MOSI)

# Hardware SPI configuration:
SPI_PORT   = 0
SPI_DEVICE = 0
mcp = Adafruit_MCP3008.MCP3008(spi=SPI.SpiDev(SPI_PORT, SPI_DEVICE))


print('Reading MCP3008 values, press Ctrl-C to quit...')
# Print nice channel column headers.
print('| {0:>4} | {1:>4} | {2:>4} | {3:>4} | {4:>4} | {5:>4} | {6:>4} | {7:>4} |'.format(*range(8)))
print('-' * 57)
# Main program loop.
while True:
    # Read all the ADC channel values in a list.
    values = [0]*8
    for i in range(8):
        # The read_adc function will get the value of the specified channel (0-7).
        values[i] = mcp.read_adc(i)
    # Print the ADC values.
    print('| {0:>4} | {1:>4} | {2:>4} | {3:>4} | {4:>4} | {5:>4} | {6:>4} | {7:>4} |'.format(*values))
    # Pause for half a second.
    time.sleep(0.5)

Is it maybe the interrupt is mentioned in the library?

Relevant Python docs: Built-in Exceptions - KeyboardInterrupt — Brian61354270
– Brian61354270, Commented Jan 7, 2023 at 16:37
For more general background, there's Signal Handling, and more specifically, termination signals from the GNU C docs. — Brian61354270
– Brian61354270, Commented Jan 7, 2023 at 16:47

chepner · Accepted Answer · 2023-01-07 16:38:14Z

1

KeyboardInterrupt is raised by the default signal handler for the interrupt signal (SIGINT). The module most likely uses the signal library to install a custom handler that produces the output you see, rather than raising KeyboardInterrupt.

answered Jan 7, 2023 at 16:38

chepner

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