Reading numbers through serial communication on Raspberry Pi

Question

I have been trying to write a program that allows my Raspberry Pi to receive numbers through serial communication. I am communicating these numbers to the Raspberry Pi using an Arduino. The Arduino serial prints a prefix character followed by the number: Serial.println("T"); Serial.println(483); In the program, I am able to identify the prefix, but when I try to read the following number I am only able to get the first digit:

ser = serial.Serial('/dev/ttyACM0', 9600, timeout = 0)

while True:
    if ser.in_waiting > 0:
        # If there's more than 20 bytes in the buffer, clear it.
        if ser.in_waiting >= 20:
            ser.reset_input_buffer()
        temp = ser.readline().decode('utf-8')
        # Check to see what the prefix of the data is
        if (temp.strip().isalpha()):
            # If we got a 'T', it's a temperature update. Save temperature as number and print
            if (temp.strip() == 'T'):
                temp = ser.readline().decode('utf-8')
                if temp.strip().isdigit():
                    number = (temp.strip())
                    print(number)

In this case, when I print(number) it outputs the number 4 and not 483. Does anyone know what is wrong?

Software with substitutions:

    if ser.in_waiting > 0:
        # If there's more than 20 bytes in the buffer, clear it.
        if ser.in_waiting >= 20:
            ser.reset_input_buffer()
        temp = ser.readline().decode('utf-8')
        # Check to see what the prefix of the data is
        if (temp.strip().isalpha()):
            # If we got a 'T', it's a temperature update. Update the temperature
            if (temp.strip() == 'B'):
                b = ser.readline()
                print([int(c) for c in b])
                temp = b.decode('utf-8')
                if temp.strip().isdigit():
                    number = (temp.strip())
                    print ("temp = " + temp)

Output after Serial.println("T"); Serial.println(483); ran three times:

[52]
temp = 4
[]
[]
[]
[]
[52]
temp = 4
[52]
temp = 4