Grab a value from one list when the value of another list equals a value-CodePudding

I am extracting data and I am getting two separate lists. One list has the dates of when this test was done and the other list has if it's approved or not. For example

TestDate_lst = ['2022-03-24', '2022-03-24', '2022-03-24', '2022-03-04', '2022-03-24',
'2021-04-20', '2021-04-20']

Action_lst = ['Decline', 'Decline', 'Decline', 'Approve', 'Approve', 'Ignore', 'Decline']

What I am trying to do is that every time there is a Decline response in Action_lst you extract the date that it was declined.

The code that I have tried is:

DateTest = []

for i in TestDate_lst:
    for a in Action_lst:
        if a == "Decline":
           DateTest.append(i)
        else:
           pass

Output:

DateTest_lst = ['2022-03-24', '2022-03-24', '2022-03-24', '2022-03-24', '2022-03-24',
'2022-03-24', '2022-03-24', '2022-03-24', '2022-03-24', '2022-03-24', '2022-03-24',
'2022-03-24', '2022-03-04', '2022-03-04', '2022-03-04', '2022-03-04', '2022-03-24',
'2022-03-24', '2022-03-24', '2022-03-24', '2021-04-20', '2021-04-20', '2021-04-20',
'2021-04-20']

Expected:

DateTest_lst = ['2022-03-24', '2022-03-24', '2022-03-24', '2021-04-20']

I know the for loop is what is causing issues, and I thought about doing a dictionary to solve this problem but wasn't sure if this was the right path to take.

CodePudding user response：

You don't need a double loop:

for i in range(len(TestDate_lst)):
    if Action_lst[i] == 'Decline':
        DateTest.append(TestDate_lst[i])

print(DateTest)

CodePudding user response：

You can use zip.

TestDate_lst = ['2022-03-24', '2022-03-24', '2022-03-24', '2022-03-04', '2022-03-24',
'2021-04-20', '2021-04-20']

Action_lst = ['Decline', 'Decline', 'Decline', 'Approve', 'Approve', 'Ignore', 'Decline']

result = [t for t,a in zip(TestDate_lst, Action_lst) if a=='Decline']

print(result)

Output:

['2022-03-24', '2022-03-24', '2022-03-24', '2021-04-20']

Check Performance:

TestDate_lst = ['2022-03-24', '2022-03-24', '2022-03-24', '2022-03-04', '2022-03-24','2021-04-20', '2021-04-20']*100_000
Action_lst = ['Decline', 'Decline', 'Decline', 'Approve', 'Approve', 'Ignore', 'Decline']*100_000

Benchmark on colab

%timeit [t for t,a in zip(TestDate_lst, Action_lst) if a=='Decline']
# 68.8 ms ± 18.5 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)

second appeoach:

%%timeit
res = []
for i in range(len(TestDate_lst)):
    if Action_lst[i] == 'Decline':
        res.append(TestDate_lst[i])

# 108 ms ± 1.27 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)