CODEWITHSUNDEEP
pythonlistlist-comprehension
Alex.Kh
Alex.Kh

Reputation: 612

List Comprehension with Multiple Conditions

At the moment I am trying to figure out how to solve a simple problem using List Comprehension. The point is to make a list and fill it with 1 at the beginning and at the end of the list. The rest elements are filled with 0.

I already tried the following:

desired_length = int(input('Enter the desired length: '))
list_=[0 if x==0 if x==desired_length-1 else x for x in range(desired_length)]
print(list_)

Edit Fixed the square brackets

And here is the code I am trying to convert:

def test():
    desired_length = int(input('Enter the desired length: '))
    list_ = []
    for i in range(desired_length):
        if i == 0 or i == desired_length - 1:
            list_.append(1)
        else:
            list_.append(0)
    print(list_)

Upvotes: 0

Views: 115

Answers (6)

Raja Sakthiyan
Raja Sakthiyan

Reputation: 31

I'm using short-circuit expression here instead of ternary condition (just like Imtinan Azhar's answer)

[int(idx==0 or idx==desired_length - 1) for idx in range(desired_length)]

Upvotes: 0

Jab
Jab

Reputation: 27485

You have 2 very easy ways of achieving the result you want.

You could use the in operator and since bool Is a subset of int Just cast it to int:

list_ = [int(i in (0, desired_length - 1)) for i in range(desired_length)]

Or just using the star operator to unpack a list of zeros of length-2 And put 1's at each end, no looping required 

list_ = [1, *([0]*(desired_length-2)), 1]

Upvotes: 2

Larissa Teixeira
Larissa Teixeira

Reputation: 116

There is a simple way to do that. Here is my code:

def test():
    desired_length = int(input('Enter the desired length: '))
    list_ = [0]*desired_length
    list_[0]=1
    list_[-1]=1

I hope I helped!

Upvotes: 0

balderman
balderman

Reputation: 23815

Here

desired_length = int(input('Enter the desired length: '))
lst = [1 if idx == 0 or idx == desired_length-1 else 0 for  idx,x in enumerate(range(desired_length))]
print(lst)

Upvotes: 0

Imtinan Azhar
Imtinan Azhar

Reputation: 1753

Firstly a dictionary is defined by {} and a list by [] you are defining a dictionary not a list.

Secondly, this is what you want 

[1 if (idx==0 or idx == (desired_length-1)) else 0 for idx in range(desired_length)]

what you are doing sets 1 at the start and end but 1,2,3 and so on in between

Thirdly, you have the condition set to put 0 at the start and end rather than 1.

Upvotes: 1

sahasrara62
sahasrara62

Reputation: 11228

using list comprehension

desired_length = int(input('Enter the desired length: '))
list_ = [(1 if i in [0,desired_length-1] else 0) for i in range(desired_length)]
print(list_)

output

Enter the desired length: 10
[1, 0, 0, 0, 0, 0, 0, 0, 0, 1]

Upvotes: 0

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