Python conversion and input validation
Text from a form or terminal is not automatically an integer. int converts valid integer text and raises ValueError for invalid numeric syntax.
Python
def parse_age(text):
try:
age = int(text)
except ValueError:
return "Invalid integer"
if age < 0:
return "Age cannot be negative"
return str(age)
print(parse_age("21"))
print(parse_age("abc"))
print(parse_age("-1"))
assert parse_age("0") == "0"