gistfile1.py

f = open('file.txt', 'w')
f.write('hi')
f.close()

# Better
with open('file.txt', 'w') as f:
    f.write('hi')   

with pytest.raises(ValueError):
    int('hi')

with SomeProtocol(host, port) as protocol:
    protocol.send(['get', signal])
    result = protocol.receive() 

class SomeProtocol:
    def __init__(self, host, port):
        self.host, self.port = host, port

    def __enter__(self):
        self._client = socket()
        self._client.connect((self.host,
                                self.port))

    def __exit__(self, exception, value, traceback):
        self._client.close()

    def send(self, payload): ...

    def receive(self): ...

SomeProtocol.__enter__() is missing return self at the end. Without it, protocol on line 12 will be None.