python byte array print() gives wrong values

Question

Using python 3, I made the following script consisting of a model class containing hundreds of bytearrays and in the same script outside of model class i am printing some of these out to verify they are correct. When i print the values some of values are not what i expected.(i put coded comments to identify these in the code below)

Here is a shortend version of my script with some of the bytearrays

`
class Model:
    def __init__(self):

        # weird values:
        self.bp_diastole_118 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02\x3b')
        self.bp_diastole_120 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02\x3c')
        self.bp_diastole_122 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02\x3d')
        self.bp_diastole_124 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02\x3e')
        self.bp_diastole_126 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02\x3f')
        self.bp_diastole_128 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02\x40')
        self.bp_diastole_160 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02\x50')

        # correct values:
        self.pupil_r_normal = bytearray(b'\xff\x01\x02\x01\x01\x00\x03\xc3')
        self.pupil_r_dilated = bytearray(b'\xff\x01\x02\x01\x01\x00\x03\xc4')
        self.pupil_r_constriced = bytearray(b'\xff\x01\x02\x01\x01\x00\x03\xc5')
        self.pupil_r_reaction_on = bytearray(b'\xff\x01\x02\x01\x01\x00\x03\xc6')
        self.pupil_r_reaction_off = bytearray(b'\xff\x01\x02\x01\x01\x00\x03\xc7')




m = Model()  

print('--------------weird value------------------')
print('bp_diastole_118 = {}'.format(m.bp_diastole_118))
print('bp_diastole_120 = {}'.format(m.bp_diastole_120))
print('bp_diastole_122 = {}'.format(m.bp_diastole_122))
print('bp_diastole_124 = {}'.format(m.bp_diastole_124))
print('bp_diastole_126 = {}'.format(m.bp_diastole_126))
print('bp_diastole_128 = {}'.format(m.bp_diastole_128))
print('bp_diastole_160 = {}'.format(m.bp_diastole_160))

print('-------------correct value--------------------')
print('pupil_r_normal = {}'.format(m.pupil_r_normal))
print('pupil_r_dilated = {}'.format(m.pupil_r_dilated))
print('pupil_r_constriced = {}'.format(m.pupil_r_constriced))
print('pupil_r_reaction_on = {}'.format(m.pupil_r_reaction_on))
print('pupil_r_reaction_off = {}'.format(m.pupil_r_reaction_off))

here is what is printed to the console:

`
--------------weird value------------------
bp_diastole_118 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02;')
bp_diastole_120 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02<')
bp_diastole_122 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02=')
bp_diastole_124 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02>')
bp_diastole_126 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02?')
bp_diastole_128 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02@')
bp_diastole_160 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02P')
-------------correct value--------------------
pupil_r_normal = bytearray(b'\xff\x01\x02\x01\x01\x00\x03\xc3')
pupil_r_dilated = bytearray(b'\xff\x01\x02\x01\x01\x00\x03\xc4')
pupil_r_constriced = bytearray(b'\xff\x01\x02\x01\x01\x00\x03\xc5')
pupil_r_reaction_on = bytearray(b'\xff\x01\x02\x01\x01\x00\x03\xc6')
pupil_r_reaction_off = bytearray(b'\xff\x01\x02\x01\x01\x00\x03\xc7')

As you can see the good values print exactly what i would expect and are identical to the values i initialized. However if you look at what was printed from the weird values you can see the last 3 characters do not match the values i initialized.

i.e.
initialized:
self.bp_diastole_118 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02\x3b')
is not the same as printed:
bp_diastole_118 = bytearray(b'\xff\x01\x02\x01\x01\x00\x02;')

Does anybody know why this is happening and how I could remedy the problem?

It's a bit of a mindfuck that you've swapped "correct" and "weird" values in the printout vs what your code supposedly does. Are you sure you're using the code you pasted vs the output you're getting? — Torxed
oops i forgot to change that part for the shortened. thanks for pointing that out. ill fix it. @Xion — Zack Jackson
I swapped them so that they would match what the model class shows thinking it would help people to visually understand. I forgot to swap at the print functions, sorry ill fix that as well @Torxed — Zack Jackson

Xion Xion · Accepted Answer · 2018-12-18T21:53:59

The problem I found is x3b through x50 they seem to be outputting the last part as special character with x50 being P. If you test using bytearray(b'\x3b') it will display the ending for you

python byte array print() gives wrong values

2 Answers