How to check function arguments type in Python All In One

How to check function arguments type in Python All In One

Python & argument type check

bug ❌

arguments type checker

#!/usr/bin/env python3
# coding: utf8

# arguments type checker ✅
def func(arg1: int, arg2: bool, arg3: str):
  # arg1
  if isinstance(arg1, int):
    print("✅ arg1 =", arg1)
  else:
    print("type error ❌, arg1 =", arg1)
  # arg2
  if isinstance(arg2, bool):
    print("✅ arg2 =", arg2)
  else:
    print("type error ❌, arg2 =", arg2)
  # arg3
  if isinstance(arg3, str):
    print("✅ arg3 =", arg3)
  else:
    print("type error ❌, arg3 =", arg3)
  print("\n")

if __name__ == "__main__":
  func(255, False, "OK")
  func(False, 255, "Error")


"""
$ py3 ./order-error-args.py
"""

$ py3 ./order-error-args.py
✅ arg1 = 255
✅ arg2 = False
✅ arg3 = OK

✅ arg1 = False
type error ❌, arg2 = 255
✅ arg3 = Error

bool is instanceof int ???

False/True => 0/1

solution

#!/usr/bin/env python3
# coding: utf8

# arguments type checker ✅
def func(arg1: int, arg2: bool, arg3: str):
  # arg1
  if isinstance(arg1, int) and not isinstance(arg1, bool):
    print("✅ arg1 =", arg1)
  else:
    print("type error ❌, arg1 =", arg1)
  # arg2
  if isinstance(arg2, bool):
    print("✅ arg2 =", arg2)
  else:
    print("type error ❌, arg2 =", arg2)
  # arg3
  if isinstance(arg3, str):
    print("✅ arg3 =", arg3)
  else:
    print("type error ❌, arg3 =", arg3)
  print("\n")

if __name__ == "__main__":
  func(255, False, "OK")
  func(False, 255, "Error")


"""
$ py3 ./order-error-args.py
"""

$ py3 ./order-error-args.py
✅ arg1 = 255
✅ arg2 = False
✅ arg3 = OK

type error ❌, arg1 = False
type error ❌, arg2 = 255
✅ arg3 = Error

demos

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rpi-ws281x

API

    def __init__(self, num, pin, freq_hz=800000, dma=10, invert=False,  brightness=255, channel=0, strip_type=None, gamma=None):
        """Class to represent a SK6812/WS281x LED display.  Num should be the
        number of pixels in the display, and pin should be the GPIO pin connected
        to the display signal line (must be a PWM pin like 18!).  Optional
        parameters are freq, the frequency of the display signal in hertz (default
        800khz), dma, the DMA channel to use (default 10), invert, a boolean
        specifying if the signal line should be inverted (default False), and
        channel, the PWM channel to use (defaults to 0).
        """

https://github.com/rpi-ws281x/rpi-ws281x-python/blob/master/library/rpi_ws281x/rpi_ws281x.py#L41

bug demo ???

# ✅
strip = PixelStrip(LED_COUNT, LED_PIN, LED_FREQ_HZ, LED_DMA, LED_INVERT, LED_BRIGHTNESS, LED_CHANNEL, LED_STRIP)

https://github.com/rpi-ws281x/rpi-ws281x-python/blob/master/examples/SK6812_white_test.py#LL34C66

refs

https://stackoverflow.com/questions/734368/type-checking-of-arguments-python

https://stackoverflow.com/questions/378927/what-is-the-best-idiomatic-way-to-check-the-type-of-a-python-variable

https://stackoverflow.com/questions/1549801/what-are-the-differences-between-type-and-isinstance

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