You’re trying to convert a string into an integer using int(), but Python throws a ValueError. That usually means the string doesn’t look like a proper number. Let’s break down why this happens and how to fix it.
age = int("twenty")This gives:
ValueError: invalid literal for int() with base 10: 'twenty'Why This Happens
The int() function expects a string that represents a valid base-10 number, like “42” or “0”. If you pass it anything else like alphabetic characters, symbols, or a decimal – it will raise this error.
Common problematic inputs:
- “abc” → letters
- “12.5” → decimal value (float)
- “” → empty string
- ” 7 ” → extra spaces (though this usually works)
Steps to Fix the Error in Python
Step 1: Print the Value Before Conversion
Always check what you’re trying to convert:
print(user_input)
age = int(user_input)Step 2: Use str.isdigit() to Check Validity
user_input = "25"
if user_input.isdigit(): age = int(user_input)
else: print("Please enter a valid number.")Note: isdigit() only works for positive integers without decimals.
Step 3: Use try-except Block for Safer Conversion
user_input = "12a"
try: age = int(user_input)
except ValueError: print("Invalid input. Please enter a number.")Step 4: Strip Whitespace and Validate
cleaned = user_input.strip()
if cleaned.isdigit(): age = int(cleaned)Step 5: Handle Decimal Numbers Properly
If the input might be a decimal (e.g., “12.5”), convert it to float instead:
number = float("12.5")Summary
The ValueError: invalid literal for int() with base 10 shows up when int() is given a string that doesn’t cleanly represent a whole number. To fix it, first inspect the input, then validate it using methods like isdigit() or a try-except block. If decimals are expected, use float() instead of int(). Clean inputs, validate early, and handle exceptions—that’s the safest way to avoid this error. If you’re building user-facing forms, APIs, or data pipelines, it pays to y who knows how to handle input validation at every layer.
