Python Morsels: SyntaxError: invalid syntax

Table of contents

1. What is a SyntaxError in Python?
2. Causes of SyntaxError: invalid syntax
3. Fixing SyntaxError: invalid syntax
4. Upgrading Python improves error messages
5. Count your parentheses
6. Misspelled, missing, or misplaced keywords
7. Subtle spacing problems
8. Forgotten quotes and extra quotes
9. Mixing up your symbols
10. Indentation errors in disguise
11. Embedding statements within statements
12. Errors that appear only in the Python REPL
13. Problems copy-pasting from the REPL
14. The line number is just a "best guess"
15. SyntaxError exceptions happen all the time

What is a SyntaxError in Python?

This is Python's way of saying "I don't understand you". Python knows that what you've typed isn't valid Python code but it's not sure what advice to give you.

When you're lucky, your SyntaxError will have some helpful advice in it:

$ python3 greet.py
  File "/home/trey/greet.py", line 10ifname=="Trey"
                     ^
SyntaxError: expected ':'

$ python3 greet.py
  File "/home/trey/greet.py", line 10ifname=="Trey"
                     ^
SyntaxError: expected ':'

But if you're unlucky, you'll see the message invalid syntax with nothing more:

$ python3.9 greet.py
  File "/home/trey/greet.py", line 4
    name
    ^
SyntaxError: invalid syntax

$ python3.9 greet.py
  File "/home/trey/greet.py", line 4
    name
    ^
SyntaxError: invalid syntax

This error message gives us no hints as to what might be going on outside of a line number and a bit of highlighting indicating where Python thinks the error occurred.

Causes of SyntaxError: invalid syntax

What are the likely causes …