Why does adding two numbers sometimes join them as text?

Quotes make these values strings. Adding strings joins their text, so "10" + "5" becomes "105". Convert valid numeric text to integers before adding when you want arithmetic. input() also returns text. In a real form or program, handle invalid input rather than assuming every string can be converted.

first = "10"
second = "5"
print(int(first) + int(second))

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