Index of a list in a nested for loop in python

Question

I have a nested loop. I want to iterate on a list of lists and check if a parameter is in a list, bring me back the list index.

parameter="Abcd"
li1=["ndc","chic"]
li2=["Abcd","cuisck"]
Li=[li1,li2]
for i in Li:
    for j in i:
        if (parameter==j):
            x=i+1
print(x)

I expect an integer like for this example x=2. But it does not work. How can I do that?

What do you expect print(Area) to output? You never defined that name... And what do you expect i+1 to be when i is a string? — trincot
– trincot, Commented May 25, 2022 at 15:59
Try to use for j in range(len(i)) and you will get the index you want — user16836078
– user16836078, Commented May 25, 2022 at 16:00
Should the list your looping through be flattened? As it is youre getting the list the parameter belongs to but not the position in that list... — Craicerjack
– Craicerjack, Commented May 25, 2022 at 16:08

Maokai · Accepted Answer · 2022-05-25 16:08:42Z

1

You didn't specify the output you are expecting, but I think you want something like this:

parameter="Abcd"
li1=["ndc","chic"]
li2=["Abcd","cuisck"]
Li=[li1,li2]
for row in Li:
    for i, j in enumerate(row):
        if parameter == j:
            print("List", Li.index(row),"Element", i)

Output:

List 1 Element 0

answered May 25, 2022 at 16:08

Maokai

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Comments

Timur Shtatland · Accepted Answer · 2022-05-25 16:03:58Z

0

Use enumerate, which returns the index and the element. Also use sets, which are faster than lists (for long lists).

parameter = "Abcd"
lst1 = ["ndc", "chic"]
lst2 = ["Abcd", "cuisck"]
lst = [lst1, lst2]
x = None

for i, sublst in enumerate(lst):
    if parameter in set(sublst):
        x = i+1
print(x)
# 2

answered May 25, 2022 at 16:03

Timur Shtatland

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2 Comments

Donnie Over a year ago

Sets are unordered and can't have duplicates, so they're not a drop in replacement, depending on exactly what you're trying to do.

Timur Shtatland Over a year ago

@Donnie: That's true, but for the exact problem in the OP sets are a good solution. If lists are preferred (perhaps for small lists), then simply use them like this: if parameter in sublst:

score 0 · Accepted Answer · 2022-05-25 16:11:25Z

0

Use numpy array. It will save you tons of time and cost.

Li = np.array([li1,li2])

Li == parameter

array([[False, False],
       [ True, False]])

row, column = np.where(Li == parameter)

row
Out[17]: array([1], dtype=int64)

edited May 25, 2022 at 16:11

answered May 25, 2022 at 16:05

user16836078

Comments

Ghislain G. · Accepted Answer · 2022-05-25 16:11:27Z

0

parameter="Abcd"
li1=["ndc","chic"]
li2=["Abcd","cuisck"]
Li=[li1,li2]

index = -1

for i in Li:
    if parameter in i:
        index = Li.index(i)
            
print(index)

You can check if something is in a list with 'in' and get the index of the element with .index, it returns the integer position in the list. Perhaps you want a tuple for the nested position ? use something like (Li.index(i), i.index(parameter)) as your return value. Don't forget to declare your return value outside your loop scope !

edited May 25, 2022 at 16:11

answered May 25, 2022 at 16:10

Ghislain G.

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