url = 'https://explorer.dash.org/insight/address/'
urlblock = url + addr
respone_block = requests.get(urlblock)
byte_string_block = respone_block.content
source_code_block = html.fromstring(byte_string_block)
xpatchblock_txid = '/html/body/div[2]/section/section/div[2]/div[2]/div[1]/table/tbody/tr[1]/td[2]'
blocktreetxid = source_code_block.xpath(xpatchblock_txid)
blocktxid = str(blocktreetxid[0].text_content())
# ====================================================
print(blocktxid)