What web3.py version do you use?

It seems you use web3 >= v6.0.0 where deprecated camelCase methods were removed in favor of snake_case ones while your code has been written for <v6.0.0.

In this case, you should replace:

• buildTransaction with build_transaction
• getTransactionCount with get_transaction_count

Do not change swapExactETHForTokens though, as it's part of the ABI.