Print the line before the corrent line

[tester_V]

Greetings!
I'm searching lines for two words "PASSED" and "FAILED"
I need to get the line before "PASSED" and the "FAILED" line.
I'm definitely doing it wrong,
the script I wrote does not get me the line I'm looking for, it actually prints the same line.

ftor = open('C:/01/prt.csv','r')
for num, el in enumerate(ftor, 1):
    el=el.strip()
    if 'PASSED' in el :

        to_gt =num-1
        print(f" BEFORE PASSED ->{to_gt} - {el}")    

        pas_fail = el.split(",")
        print (f"    {num}    {pas_fail[9]} - {el}")
        print("")
    elif 'FAILED' in el :
        to_gt =num-1
        print(f" BEFORE FAILED ->{to_gt} - {el}")     

        pas_fail = el.split(",")
        print (f"    {num}    {pas_fail[9]} - {el}")
        print("") 

ftor.close()

Thank you!

[deanhystad]

I don't understand your code, but if you just need to remember the last line for some reason:

prev_line = None
for line in file:
    do stuff(line, prev_line)
    prev_line = line 

[tester_V]

Awesome!
Thank you, guys!

[Pedroski55]

Are you guys all in the same class? I still have the csv sample from some other thread about finding "Failed"

The pass/fail column is column F

How big is your ftor?

import sys

path2csv = '/home/pedro/myPython/csv/csv/YE2531_20220609_074155_Tester1.csv'

with open(path2csv) as mycsv:
    count = 1
    data = mycsv.readlines()
    print('The size of data is', sys.getsizeof(data))
    fails = []
    for line in data:
        print('The size of line is', sys.getsizeof(line))
        if 'Failed' in line:
            print('line', count, 'failed')
            print('of course, the previous line was', count-1)
            fails.append(count)
        count +=1

for f in fails:
    print('fail line number is', f)

[tester_V]

That is funny!
No, we are not in the same class for sure.
I'm a 61-year-old guy trying the get some data from machines...

It is hard to learn anything if you are that old...

[Larz60+]

Youngster!

[tester_V]

Larz60+!
You are DA MAN

[ndc85430]

It's a shame you're on Windows. Otherwise, sounds like a job for grep and head probably.

[Pedroski55]

I just asked if ftor is very big, maybe millions of lines, because then a function with yield may be better.

Then you need the experts here to design that, yield confuses me!

[Gribouillis]

One can use itertools.pairwise()

for lineno, (prev_line, line) in enumerate(itertools.pairwise(ftor), 2):
    ... # do something with line and prev_line