Chris Angelico <[email protected]>:
> Simple rule of thumb: Never use 'is' with strings or ints. They're
> immutable, their identities should be their values. Playing with 'is'
> will only confuse you, unless you're specifically going for
> introspection and such.
Here's a use case for "is" with strings (or ints):
class Connection:
IDLE = "IDLE"
CONNECTING = "CONNECTING"
CONNECTED = "CONNECTED"
DISCONNECTING = "DISCONNECTING"
DISCONNECTED = "DISCONNECTED"
def __init__(self):
self.state = IDLE
def connect(self, address):
...
self.state = CONNECTING
...
def disconnect(self):
...
if self.state is CONNECTED:
...
The state objects could have been defined like this:
IDLE = object()
CONNECTING = object()
CONNECTED = object()
DISCONNECTING = object()
DISCONNECTED = object()
However, strings have the advantage in troubleshooting:
sys.stderr.write("state = {}\n".format(self.state))
Marko
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