python · Python
The message
ValueError: invalid literal for int() with base 10: '3.5'
What it means
You handed int() a string it cannot read as a whole number, and the text in quotes is that string. A decimal point as in '3.5', an empty string, an input with a trailing newline, or a thousands separator as in '1,000' are the usual causes. For a decimal, int(float(s)) works in two steps — but it truncates the fraction away rather than rounding — and for anything a person typed, wrapping it in try/except ValueError is the honest fix.
The fix
There is no one-line command for this. The explanation says what to look at instead.
- Printed by
- python
- Python
- 18
A Python traceback splits the answer in two — the last line says what went wrong, the frames above it say where — so reading only the last line gives you the name and loses the place, and for the value-is-missing errors such as NoneType and KeyError the cause almost always sits in a frame above the one that crashed.
Reading an error message
- Read from the first line down. The lower you go the more it is about the tool’s internals; the cause is usually at the top.
- If there is a file and a line number, start there — not the top stack frame, but the topmost line that names a file you wrote.
- Search the message verbatim, but strip your own paths and variable names first; those are what stop the search from matching.
- The same condition is worded differently across tool versions. If results look wrong, add the version number to the query.
- Before pasting a fix, check what it throws away. Some of these cannot be undone.
Common questions
Q. What does “ValueError: invalid literal for int() with base 10: '3.5'” mean?
You handed int() a string it cannot read as a whole number, and the text in quotes is that string. A decimal point as in '3.5', an empty string, an input with a trailing newline, or a thousands separator as in '1,000' are the usual causes. For a decimal, int(float(s)) works in two steps — but it truncates the fraction away rather than rounding — and for anything a person typed, wrapping it in try/except ValueError is the honest fix.
Q. How do I fix it?
There is no one-line command. The explanation above says what to look at instead.
Q. Which tool prints this?
python. It sits under Python, and the message runs to 9 words.