python .format(*str) returns 5348 instead of 50

Question

I have this code to format the received data from Serial port to 2 variables it receives 'v=220f=50' and format it to

 reads = ser.readline()                # data received is 'v=220f=50'         
 voltage = int('{2}{3}{4}'.format(*reads))
 freq = '{7}{8}'.format(*reads)

so voltage = 220 and freq = 50 but i get voltage = 505048 and freq = 5348 instead!, I tried casting them to int() but nothing changed. maybe it's some sort of encoding.

ps: I want to store them into a file so no need to cast them to integers:

fw.write('Voltage is: {0};\t  Frequency is: {1}\n'.format(voltage, freq))

Answer 1

You have a bytes object from ser.readline(). You should first convert to string with .decode:

>>> reads = b'v=220f=50'
>>> voltage = int('{2}{3}{4}'.format(*reads))
>>> voltage
505048
>>> voltage = int('{2}{3}{4}'.format(*reads.decode()))
>>> voltage
220

I would also suggest you look into parsing the values using regex. The current approach would easily break when the length of any of the values change.