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Issues with Lambda Function - fad3r - May-22-2018
Hi,
I am trying to wrap my head around lambda but I am running into issues.
The homework question is: Write a lambda function that takes a list my_list and returns a list which includes only even numbers
my_list = [1, 5, 4, 6, 8, 11, 3, 12] test = lambda my_list: my_list % 2 == 0 print test(my_list)I feel like that should do it but I get an error when I try to run it. Not sure what is wrong with my logic.
RE: Issues with Lambda Function - buran - May-22-2018
you need list comprehension in the lambda
RE: Issues with Lambda Function - ThiefOfTime - May-22-2018
The Problem is that any numerical operand is only defined for values (int, double, long, etc.) not for lists.
the first solution that pops into my mind is:
my_list = [1,5,4,6,8,11,3,12] test = lambda mylist: [el for el in mylist if el % 2 == 0] print(test(my_list))what you are doing is to get every element in the list, check if it is even and pack all even elements into a new list.
If the amount of elements becomes too high use numpy instead, there you can also use masks. But for small lists this would be a solution. but since you are constructing a new list you could use the list comprehension without the explizit function and lambda, but that depends on what you want to do with the lambda :)
RE: Issues with Lambda Function - fad3r - May-22-2018
(May-22-2018, 03:51 PM)buran Wrote: you need list comprehension in the lambda
The list comp does help but it returns boolean expression unless I did it wrong?
my_list = [1, 5, 4, 6, 8, 11, 3, 12] test = lambda my_list: [my_list % 2 == 0 for my_list in my_list] print (test(my_list))
RE: Issues with Lambda Function - buran - May-22-2018
@ThiefOfTime already post the right solution
My code is the same
test = lambda my_list: [x for x in my_list if not x%2]
RE: Issues with Lambda Function - fad3r - May-22-2018
(May-22-2018, 03:58 PM)ThiefOfTime Wrote: The Problem is that any numerical operand is only defined for values (int, double, long, etc.) not for lists.
the first solution that pops into my mind is:
my_list = [1,5,4,6,8,11,3,12] test = lambda mylist: [el for el in mylist if el % 2 == 0] print(test(my_list))what you are doing is to get every element in the list, check if it is even and pack all even elements into a new list.
If the amount of elements becomes too high use numpy instead, there you can also use masks. But for small lists this would be a solution. but since you are constructing a new list you could use the list comprehension without the explizit function and lambda, but that depends on what you want to do with the lambda :)
Yup this totally solves it. I have to spend some time to understand why yours works your way and mine at the bottom creates a boolean. The tip on the numerical operand piece was super helpful. I totally didnt know that.