# This is the inputlist input_list =[1,0,3,2,0,1,0] and I want output_list as [1,1,2,3,0,0,0] How to solve this?

## Question:

``````input_list =[1,0,3,2,0,1,0]

for a in input_list:
if input_list[a] != 0:
input_list[a] = a
else:
input_list[a] = 0

print(input_list)
``````

Tried this but getting output as input_list =[1,0,3,2,0,1,0]

``````for a in input_list:
if input_list[a] != 0:
input_list[a] = a
else:
input_list[a] = 0

print(input_list)
``````

You can make a custom sort where you give `0` infinite weight so it appears at the end of the sorting order.

``````output_list = sorted(input_list, key=lambda x: x if x != 0 else float('inf'))
``````

getting output as input_list

No, your code gives `[0, 0, 3, 3, 0, 1, 0]`, because you use the values as indexes, `for a in input_list` iterates over values, then you use them `input_list[a]` as indexes

What you need is sorting, `x or float('inf')` expression takes `inf` in case the value of `x` is 0 (putting it at the end of the list), else it takes the value of `x`

``````input_list = [1, 0, 3, 2, 0, 1, 0]
result = sorted(input_list, key=lambda x: x or float('inf'))
print(result)
``````
``````input_list =[1,0,3,2,0,1,0]
input_list.sort()
new_list = [el for el in input_list if el != 0] + [el for el in input_list if el == 0]
``````

Output:

``````[1, 1, 2, 3, 0, 0, 0]
``````

I think the cleanest way to solve this is:

``````import math
input_list =[1,0,3,2,0,1,0]

input_list = sorted(input_list, key=lambda x: x if x!=0 else math.inf)
``````

Which is sorting like one would usually do, but giving the `0` a weight of `inf` (infinite) such that it’s always the last item.

There are already some good answers, here is just one more alternative approach, albeit more concise and little tricky:

Here it’s use the "True" and "False" of each number and its identity to move all "True" (number is zero) to the end of list.

``````
L = [1,0,3,2,0,1,0]

ans = sorted(L, key=lambda x: (x ==0, x))

print(ans)
[1, 1, 2, 3, 0, 0, 0]

``````

If you don’t want to create a new list, you can use the same list as this way:

``````L[:] = sorted(L, key=lambda x: (x ==0, x))
``````
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