Download a multifile-verified contract from Etherscan as a simple flattened contract.

etherscan-get-multifile.py

from etherscan import Etherscan
import os
import json
from time import sleep

# setup
ethscan = Etherscan('YOUR_API_KEY_HERE')
# NOTE: must be a multi-verified contract to work. Staked Aave used as example here
address = "0x4da27a545c0c5b758a6ba100e3a049001de870f5"   

print('getting multi-file data for ' + str(address) + '...')
# get source from etherscan
etherscan_result = ethscan.get_contract_source_code(address)
# get source code section
source_code = etherscan_result[0]['SourceCode']
# remove outer brackets and loads into json
source_code = json.loads(source_code[1:-1]) 

source_code_file = open(os.getcwd() + '/' + address + '.sol', "w")
source_code_contracts = source_code['sources']
for contract_name in source_code_contracts:
    source_code_file.write("// " + contract_name + "\n\n")
    source_code_file.write(source_code_contracts[contract_name]['content'] + "\n\n")
source_code_file.close()
print('Done!')