You'll meet the same handful of errors again and again. Knowing them by name saves time:

• SyntaxError — a typing-rule mistake (missing : or )).
• NameError — a name that doesn't exist (often a typo).
• TypeError — mixing types that don't go together, like text plus number.
• IndexError — asking for a list position that isn't there.
• KeyError — asking a dict for a key it doesn't have.

Run it: that's an IndexError. Read the last line, and the fix is usually quick.