PySerial: how to understand that the timeout occured while reading from serial port?

Question

I'm using PySerial to read from serial port like in the code below. CheckReadUntil() read output of the command that I send to serial port until the sequence of symbols readUntil are in the serial output.

...

self.ser = serial.Serial(comDev, 115200, timeout=10)

...

#Function that continue to read from Serial port until 'readUntil' 
#sequence of symbols appears
def CheckReadUntil(self, readUntil):
    outputCharacters = []
    while 1:
        ch = self.ser.read()
        outputCharacters += ch
        if outputCharacters[-len(readUntil):]==readUntil:
            break
    outputLines = ''.join(outputCharacters)
    return outputLines

However, if there is no sequence readUntil (for any reason), I'm just stuck in the function CheckReadUntil() forever. The setting timeout=10 sets up timeout so I'm stuck in a loop that iterates every 10 seconds and does nothing, just waiting.

How it is possible to understand that there was a timeout event so I may exit the infinite loop? Output length may be different.

Answer 1

UPDATE (previous answer was not correct, this is the working code from @konstantin):

...

self.ser = serial.Serial(comDev, 115200, timeout=10)

...

#Function that continue to read from Serial port until 'readUntil' 
#sequence of symbols appears
def CheckReadUntil(self, readUntil):
    outputCharacters = []
    while 1:
        ch = self.ser.read()
        if len(ch) == 0:
            break
        outputCharacters += ch
        if outputCharacters[-len(readUntil):]==readUntil:
            break
    outputLines = ''.join(outputCharacters)
    return outputLines