Python error explained
ValueError: what it means and how to fix it
The type is right but the value inside it is not.
The message
ValueError: invalid literal for int() with base 10: 'twelve'What it means
int() can turn the text "12" into the number 12, but it cannot make a number out of "twelve" or "12.5". The value has the right type (text) but the wrong content.
Common causes
- Converting text that contains letters or spaces
- Using int() on a decimal like "3.5" (use float())
- Empty input when the user just pressed Enter
Example that raises it
answers = ["12", "7", "twelve", "3"]
total = 0
for a in answers:
total += int(a)
print("Total:", total)
The fix
answers = ["12", "7", "twelve", "3"]
total = 0
for a in answers:
if a.isdigit():
total += int(a)
else:
print("Skipping", a)
print("Total:", total)
Tip: Check first with .isdigit(), or wrap the conversion in try and except ValueError to handle bad input gracefully.
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