CODEWITHSUNDEEP
pythonlistindexing
user7755
user7755

Reputation: 31

Python: Adding element to list at index with the same value

I have a list containing a number of ints and adding them to a second list at the index matching their value. The second list has already bin filled with placeholders ("X"). i.e:

firstlist = [2, 3, 5]

with the output:

secondlist = ['X', 'X', 2, 3, 'X', 5, 'X', 'X']

What is the best way to do so? Any help greatly appreciated!

Upvotes: 1

Views: 1590

Answers (4)

user11844902
user11844902

Reputation:

Let's say you need to make a function YourFunc(inputlist,length) where inputlist argument is the list for input and length is the argument for the length of the list for output. So, according to your question, inputlist=[2,3,5] and length=8.

def YourFunc(inputlist,length):
        out=[]
        for X in range (0,length):
                if inputlist.count(X)==1:
                         out.append(X)
                elif inputlist.count(X)==0:
                         out.append('X')
        print(out)

YourFunc([2,3,5],8)

So, this is how I usually do. In this function a loop is running from 0to length. If the is element is not in inputlist then 'X' is inserted in output list out. If not, then the number in the loop is inserted.

Upvotes: 0

GeeTransit
GeeTransit

Reputation: 1468

This will take a list argument and put them into a new list to be returned by the function.

def list_fill(first_list, fill, length=None):
    return [(i if i in first_list else fill) for i in (range(max(first_list) + 1) if length is None else range(length))]

How list_fill works:

The first_list argument includes the indexes to be changed.
The fill argument is what the empty spaces should be.
The third optional length argument specifies the length of the output. If left blank, it will take the max index specified in first_list.

Upvotes: 1

Chyza
Chyza

Reputation: 1

You could use .insert() if you want to keep the stuff that's already in secondlist.

firstlist = [2, 3, 5]
secondlist = ['X', 'X', 'X', 'X', 'X']

for x in range(len(firstlist)):
    secondlist.insert(firstlist[x], firstlist[x])

print(secondlist)

Upvotes: 0

hqkhan
hqkhan

Reputation: 483

Are you looking for something as simple as this:

firstlist = [2, 3, 5]
secondlist = ['X']*10

for index in firstlist:
    secondlist[index] = index

print(secondlist)
# ['X', 'X', 2, 3, 'X', 5, 'X', 'X', 'X', 'X']

Could have a dict for firstlist with indices for key and the value you want to place as values for the dict.

Upvotes: 0

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