Python : select a specific line from text

Question

i'm trying to make a code that :

• open a text file
• go to the lines that start with "Start"
• go to line 3 from the lines that start with "start" (previously selected)
• check if that line contain " contain" word

if yes = print " ok " :

str1 = "Start"

with open("C:...test.txt") as file:
for line in file:
    if str1 in line:
        if "contain" in line:
            print "OK"
        else:
            print "NOK"

i need to integrate the " 3rd line" condition

Answer 1

For better memory usage you can use enumerate for line number tracking:

str1 = "Start"
fp = open("C:...test.txt")
check = 0
for i,line in enumerate(fp):
    if str1 in line:
        check = i
        continue
    if "contain" in line and (i == check + 3):
        print "OK"
    else:
        print "NOK"

Here i == check + 3 condition will check your 3rd line condition.