Getting error in finding time.time() value in python

[Lakshana]

while True:

    Signal=mcp.read_adc(adc_number)  # The read_adc function will get the value of the specified channel and the Signal will hold the incoming raw digital data
    if(Signal>thresh) and (i<=5):
        if i==0:
            time1=int(time.time()*1000)
        c=c+1
        i=i+1
        time2=int(time.time()*1000)
    t=time2-time1
    rate=t/5
    rate=60000/rate
    print(rate) # BPM
    time.sleep(0.005)

I wrote this program for measuring the beats/minute(BPM) from a pulse sensor. This code shows an error like time2 and time1 not defined. Is this code correct for finding the BPM value from pulse sensor?

[wavic]

Both time1 and time2 are in if condition block of code. If the condition is False they will not be created.