Finding the max element in a List

I have to find the max element in a list while filtering out all of the items inside of it that aren’t an integer or a float. So far I have this code and it seems to work except when giving the list [1, ]. I get an error saying that the list is empty and I can’t find the max element.

def max_args(lst):
    if len(lst) == 0:
        return None
    for item in lst:
        if type(item) != [int or float]:
            lst.remove(item)
    return max(lst)

Answer

You can’t check type like that. You need to check using isinstance. Also, you can’t do a for loop and do lst.remove(item) the counter will get messed up.

I recommend you do a simple program to test it out. Here’s an example for you.

x = [2,'c',4.0,{'d':5},[6,7],8,(9,10)]
print (x)
for i,val in enumerate (x):
    print ('value at position : ',i, 'is : ', val)
    if not (isinstance(val,int)):
            x.remove(val)

The above code is supposed to iterate through each element of list x. However, as you can see, it skips 4.0 and [6,7]. The reason, you removed x[1] and it resulted in 4.0 getting assigned to position x[1]. Similarly for [6,7] It moved one position to the left but your for loop iteration couldn’t catch it.

The output of the above code will be:

[2, 'c', 4.0, {'d': 5}, [6, 7], 8, (9, 10)]
value at position :  0 is :  2
value at position :  1 is :  c
value at position :  2 is :  {'d': 5}
value at position :  3 is :  8
value at position :  4 is :  (9, 10)

Instead, your code should be as follows:

def max_args(lst):
    print (lst)
    i = 0

    while i < len(lst):
        if not (isinstance(lst[i], (int,float))): 
            lst.pop(i)
        else: 
            i +=1

    if len(lst) == 0:
        return None
    else:
        return max(lst)

x = max_args([1,'a',3,'b',5.0])
print (x)
x = max_args([2,'c',4.0,{'d':5},[6,7],8,(9,10)])
print (x)
x = max_args(['a'])
print (x)
x = max_args([7])
print (x)
x = max_args([1,])
print (x)
x = max_args([1,2,3,4,5,6])
print (x)

The output will be as follows:

[1, 'a', 3, 'b', 5.0]
5.0
[2, 'c', 4.0, {'d': 5}, [6, 7], 8, (9, 10)]
8
['a']
None
[7]
7
[1]
1
[1, 2, 3, 4, 5, 6]
6