Get the length of certain values from list

Question

I would like to get the length of certain values in a list like:

lst=['ID_CYTY', 'CITY', 'ID_STATE', 'STATE', 'ID_COUNTRY', 'COUNTRY', 'AGE', 'SEX', 'NAME', 'P', 'A1', 'PR', 'V', 'Z', 'M1', 'D1', 'R1', 'CPD', 'CA', 'IN', 'ND', 'I', 'C', 'W', 'NZ', 'EG', 'LOS', 'TO', 'LS', 'EST', 'TR', 'OBS', 'RUT']

I just have another list like:

lst2=['P', 'A1', 'PR', 'V', 'Z', 'M1', 'D1', 'R1', 'CPD', 'CA', 'IN', 'ND', 'I', 'C', 'W']

I would like to get the length of the values before and after lst2 that are inside lst but the issue here is that lst could change in length from ID_CITY to NAME and NZ to RUT , I mean it could have more or less strings after P to W . Also, do not have to use the names of the strings because they could be different from the 0 index to the last index, example:

lst=['CITY', 'ID_STATE', 'STATE', 'ID_COUNTRY', 'COUNTRY', 'AGE', 'SEX', 'A1', 'P', 'PR', 'V', 'Z', 'M1', 'D1', 'R1', 'CPD', 'CA', 'W', 'ND', 'I', 'C', 'IN', 'NZ', 'LOS', 'TO', 'LS', 'EST', 'TR', 'OBS']

I believe it could be done getting the length of the lst2 and then doing some list indexing to get lengths inside lst .

The lst2 it could have theirs strings mixed but it doesn't matter because it must have the same extension from P to W no matter if starts or ends with those strings.

Note: I would like to get the values before and after lst2 in lst in individual list.

What I mean with before and after lst2 inside lst is: In the first case it would be: The length before P to W :

9

the length from NZ to RUT :

9

But this could be different just how I mentioned before.

Answer 1

See Python: return the index of the first element of a list which makes a passed function true for how to find the index in a list of the first element that matches a condition.

In this case, the length of the list before lst2 is the index of the first element that's in lst2 .

before = next(i for i,v in enumerate(lst) if v in lst2)

To get the length of the list after lst2 , do the same thing but reverse lst first.

after = next(i for i,v in enumerate(lst[::-1]) if v in lst2)

Answer 2

#lst=['ID_CYTY', 'CITY', 'ID_STATE', 'STATE', 'ID_COUNTRY', 'COUNTRY', 'AGE', 'SEX', 'NAME', 'P', 'A1', 'PR', 'V', 'Z', 'M1', 'D1', 'R1', 'CPD', 'CA', 'IN', 'ND', 'I', 'C', 'W', 'NZ', 'EG', 'LOS', 'TO', 'LS', 'EST', 'TR', 'OBS', 'RUT']
lst=['CITY', 'ID_STATE', 'STATE', 'ID_COUNTRY', 'COUNTRY', 'AGE', 'SEX', 'A1', 'P', 'PR', 'V', 'Z', 'M1', 'D1', 'R1', 'CPD', 'CA', 'W', 'ND', 'I', 'C', 'IN', 'NZ', 'LOS', 'TO', 'LS', 'EST', 'TR', 'OBS']
lst2=['P', 'A1', 'PR', 'V', 'Z', 'M1', 'D1', 'R1', 'CPD', 'CA', 'IN', 'ND', 'I', 'C', 'W']

for i in lst:
    if i in lst2:
        start = lst.index(i)
        break
for i in lst[::-1]:
    if i in lst2:
        end = lst.index(i)
        break

print(len(lst[:start]))
print(len(lst[end:-1]))

Now even if both lists changed it finds the first and last value to calculate from

Answer 3

You could use

start = lst.index(lst2[0])

This will give you the position, in lst, of the first value in lst2

end = lst.index(lst2[-1])

This will give you the position, in lst, of the last value in lst2

print(len(lst[0:start]))
print(len(lst[end:-1]))

This prints the lengths between the values

Answer 4

This does what comment 'What I was thinking is first get the len(lst2) and then do some string indexing to get the first and last values in differents variables. The len of lst2 always would be a section or slide of lst. –' says.

lst=['ID_CYTY', 'CITY', 'ID_STATE', 'STATE', 'ID_COUNTRY', 'COUNTRY', 'AGE', 'SEX', 'NAME', 'P', 'A1', 'PR', 'V', 'Z', 'M1', 'D1', 'R1', 'CPD', 'CA', 'IN', 'ND', 'I', 'C', 'W', 'NZ', 'EG', 'LOS', 'TO', 'LS', 'EST', 'TR', 'OBS', 'RUT']
lst2=['P', 'A1', 'PR', 'V', 'Z', 'M1', 'D1', 'R1', 'CPD', 'CA', 'IN', 'ND', 'I', 'C', 'W']

legnth_1= len(lst[:lst.index(lst2[0])])
legnth_2 =  len(lst[lst.index(lst2[-1])+1:])

print(legnth_1)
print(legnth_2)


>>> 9
>>> 9

Answer 5

lst=['ID_CYTY', 'CITY', 'ID_STATE', 'STATE', 'ID_COUNTRY', 'COUNTRY', 'AGE', 'SEX', 'NAME', 'P', 'A1', 'PR', 'V', 'Z', 'M1', 'D1', 'R1', 'CPD', 'CA', 'IN', 'ND', 'I', 'C', 'W', 'NZ', 'EG', 'LOS', 'TO', 'LS', 'EST', 'TR', 'OBS', 'RUT']
lst2=['P', 'A1', 'PR', 'V', 'Z', 'M1', 'D1', 'R1', 'CPD', 'CA', 'IN', 'ND', 'I', 'C', 'W']

start = lst.index(lst2[0])
end = lst.index(lst2[-1])

print(len(lst[:start]))
print(len(lst[end:-1]))

>>>
9
9
>>>

Even if the list changes it still returns the difference

lst=['CITY', 'ID_STATE', 'STATE', 'ID_COUNTRY', 'COUNTRY', 'AGE', 'SEX', 'A1', 'P', 'PR', 'V', 'Z', 'M1', 'D1', 'R1', 'CPD', 'CA', 'W', 'ND', 'I', 'C', 'IN', 'NZ', 'LOS', 'TO', 'LS', 'EST', 'TR', 'OBS']

>>>
8
11
>>>