Question

How to mask a number with stars except the last 4 digits in Python

Answer 1

def mask_number(val: str | int, mask_char: str = "*", visible_count: int = 4) -> str:
    s = str(val)
    if len(s) <= visible_count:
        return s  # Too short to mask
    
    return mask_char * (len(s) - visible_count) + s[-visible_count:]

# Example Usage
card_number = "1234567890123456"
print(mask_number(card_number))  # Output: ************3456
print(mask_number(9876543210))    # Output: ******3210



'''
run:

************3456
******3210

'''

 

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Answer 2

def mask_digits_only(val: str, visible_count: int = 4) -> str:
    # Find positions of all digits
    digit_indices = [i for i, char in enumerate(val) if char.isdigit()]
    
    # Identify which digit positions to mask (all except the last `visible_count`)
    to_mask = set(digit_indices[:-visible_count])
    
    return "".join("*" if i in to_mask else char for i, char in enumerate(val))

# Example Usage
formatted_card = "1234-5678-9012-3456"
print(mask_digits_only(formatted_card))  # Output: ****-****-****-3456


'''
run:

****-****-****-3456

'''

 

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