Pythonic way of checking bit values

Question

I have this set of constants declarations

    self.POUTPUT = 1
    self.PPWM = 2
    self.PINPUT = 4
    self.PUNUSED = 8
    self.PSONAR = 16
    self.PULTRA = 32
    self.PSERVOD = 64
    self.PSTEPPER = 128
    self.PCOUNT = 256
    self.PINPUTDOWN = 512
    self.PINPUTNONE = 1024

What is the pythonic way of checking whether a value matches any of the input states (4,512 and 1024) please? Extra info: I'd normally just use bit pattern checking in simpler languages but I wondered if there was a better way in Python :) Basically it is that each pin can have one of the I/O states above but if a pin is any of of the input values then one action occurs e.g if pin == 4 or 512 or 1024 -> do something

Answer 1

Testing for set membership (which is what you seem to be doing) is best done using a set.

self.input_states = {self.PINPUT, self.PINPUTDOWN, self.PINPUTNONE}

# later
if value in self.input_states:
    do_something()

Of course you could handle this in a variety of essentially-identical ways, but one way or another you have to encode some knowledge as to which of these magic numbers are "input states".

---

Now if, as has been suggested, what you actually want is to do some bit-masking or tests based on whether a particular bit is set, then you want to take a look at the Python bitwise operators. In particular, to see if a value is equal to one of the ones you've got there, you'd use the bitwise and, which is denoted by & in Python. Joran's answer covers this use well, but the basic idea is:

if value & self.PINPUT: # Value has a 1 in the PINPUT bit (bit 3)
    do_something()

Or if all of those input values trigger the same action:

if any(value & p for p in (self.PINPUT, self.PINPUTDOWN, self.PINPUTNONE)):
    do_something()

Answer 2

if SOME_DATA & self.PINPUTNONE:  # do somethign

is how people usually do it

to check alot

ANY = self.POUTPUT | self.PPWM | self.PINPUT | self.PUNUSED |  self.PSONAR  ...
if some_data & ANY: #do something