Python - Using List Comprehension to duplicate an array and replace elements

Question

I have a list:distance = [0,6,6,maxsize]

How can I use list comprehension to create a new list with every maxsize element replaced with a -1 and with every 0 removed?

I want the result as this:

distance1 = [6,6,-1]

I have tried this so far but it's a syntax error:

distance1=[-1 if v == maxsize else v if v != 0 for v in distance]

Thanks in advance!

Edit: maxsize is the largest positive integer supported In pythons regular integer type.

I think your syntax error is that you're nesting ternaries without giving the second ternary an else statement. — Jack Homan
– Jack Homan, Commented Nov 3, 2017 at 21:29
maxsize is the largest positive integer supported In pythons regular integer type. I'm sorry I should have specified this in the original post. — StarLlama
– StarLlama, Commented Nov 3, 2017 at 21:31
If I do something like this and add another else statement: asdf=[-1 if v == maxsize else v if v != 0 else v for v in distance], it doesn't get rid of the zeroes. Any idea how I can add the second else statement and also get rid of the zeroes? — StarLlama
– StarLlama, Commented Nov 3, 2017 at 21:36
Check out this post for info on max int value - stackoverflow.com/questions/9860588/… — Jack Homan
– Jack Homan, Commented Nov 3, 2017 at 21:41

Jack Homan · Accepted Answer · 2017-11-03 21:25:34Z

3

Is maxsize a variable, the length of the array or a string?

distance1 = [-1 if v == maxsize else v for v in filter(lambda x: x, distance)]

answered Nov 3, 2017 at 21:25

Jack Homan

4132 silver badges6 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

I'm sorry, I should have specified this. Maxsize is the largest integer supported by Pythons integer type. You can import it: from sys import maxsize