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Button Callback Regular Expression

When a IRQ is called for a button press, we are passed an event that tell us what pin gets called. Unfortunately, MicroPython does not provide a method to just get the integer of the pin, which we need of all our buttons use a single IRQ function but need to do different tasks based on which button is being used.

The pin number is buried within the GPIO string like this:

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Pin(GPIO15, mode=IN, pull=PULL_UP)

We need to have a function that we can pass this string and it will just return the integer of the GPIO. It does this using the regular expression (re) function within MicroPython.

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import re

def extract_gpio_pin(input_string):
    # Use a regular expression to find the GPIO number
    match = re.search(r"GPIO(\d+)", input_string)
    if match:
        # Convert the extracted number to an integer to remove leading zeros
        return int(match.group(1))
    else:
        # Return None if no match is found (or raise an exception if that's preferable)
        return None

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# Test the function with examples including if the returned values have leading zero
print(extract_gpio_pin("Pin(GPIO15, mode=IN, pull=PULL_UP)"))  # Output: 15
print(extract_gpio_pin("Pin(GPIO7, mode=IN, pull=PULL_UP)"))   # Output: 7
print(extract_gpio_pin("Pin(GPIO03, mode=IN, pull=PULL_UP)"))  # Output: 3

Here is the regular expression line

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match = re.search(r"GPIO(\d+)", input_string)

This function will look into the input_string for the letters "GPIO" followed by a decimal digit. It will then return that decimal digit as a string to the match variable.

It uses a regular expression pattern r"GPIO(\d+)" to find and extract the GPIO number: - GPIO matches the literal characters "GPIO" - (\d+) is a capturing group that matches one or more digits: - \d matches any digit (0-9) - + means "one or more times" - The parentheses () create a capturing group so we can extract just the number

The re.search() function looks for this pattern anywhere in the input string and returns a match object if found a match.

If a match is found (if match): - match.group(1) gets the text from the first capturing group (the digits) - int() converts the string of digits to an integer - This automatically removes any leading zeros (so "03" becomes 3)

If no match is found, it returns None.