This is a SyntaxError that confuses many beginners, especially if they are trying to format numbers neatly in their code. The message SyntaxError invalid decimal literal is a common error encountered when making a mistake in writing numbers in Python code.
It means: You tried to write a number that starts with a zero, but it isn’t a valid “octal” (base-8) number.
The Cause
In Python (and many other languages), a number starting with 0 is not treated as a normal “decimal” (base-10) number.
0o(zero-oh) means the number is Octal (base-8).0x(zero-ex) means the number is Hexadecimal (base-16).0b(zero-bee) means the number is Binary (base-2).
Problem Code: You are probably trying to align your numbers, like this:
week_1_sales = 150 week_2_sales = 90 week_3_sales = 05 # CRASH!
Error: SyntaxError: invalid decimal literal
Python sees 05 and thinks you might be trying to write an octal number (because of the 0), but it’s not a valid format. In modern Python 3, this is just disallowed to prevent confusion.
The Fix: Just Remove the Leading Zero
Numbers don’t need leading zeros for alignment.
week_1_sales = 150 week_2_sales = 90 week_3_sales = 5 # Correct!
If you are trying to print a number with leading zeros (for a report or a clock), you must do it with an f-string.
Correct Way to Format:
hour = 9
minute = 5
# Use :02 to mean "pad with 0s to be 2 digits wide"
print(f"The time is {hour:02}:{minute:02}")
# Output: The time is 09:05
