python - How to skip making a 'sentence(s)' if the the integer in the list is a zero?

Question

I didn't know how to title this. It might've been a little confusing. If this is a duplicate, sorry; please lead me to the answer page.

In this example code, sometimes the "difference" is 0. How can I remove 'statements' that have 0 in them? (See below for details)

classlist = ['CLASS1', 'CLASS2', 'CLASS3', 'CLASS4', 'CLASS5', 'CLASS6', 'CLASS7']
gradelist1 = ['69.8', '73', '89', '0', '93', '57']
gradelist2 = ['95.3', '79', '84', '0', '68', '63']

def gradeChangeShow():
    difference = []
    try:
        for i in range(len(gradelist1)):
            difference.append(int(float(gradelist2[i])) - float(gradelist1[i]))
        difference = ["{:.1f}".format(x) for x in difference]
    except ValueError:
        difference.append('0')
    difference = [x for x in difference if x != '0']
    statement = [f'
{c.rstrip()}: {d}' for c, d in zip(classlist, difference)]
    comma_delete = ','.join(statement)
    return comma_delete.replace(',', '')

print(gradeChangeShow())

This is what comes out from the code above:

CLASS1: 25.2 
CLASS2: 6.0  
CLASS3: -5.0 
CLASS4: 0.0  
CLASS5: -25.0
CLASS6: 6.0

How I want it to come out:

CLASS1: 25.2 
CLASS2: 6.0  
CLASS3: -5.0 
CLASS5: -25.0
CLASS6: 6.0

question from:https://stackoverflow.com/questions/65926218/how-to-skip-making-a-sentences-if-the-the-integer-in-the-list-is-a-zero

Answer 1

When you tried to filter your results, you used an integer 0 value as the target. Since your values are strings with decimal points, there is no way this can ever work for you.

Instead, make sure you compare against the same types. You could filter against '0.0', but this will fail if you ever change the precision in your strings. I recommend that you convert the value to numeric, and compare against that.

statement = [f'
{c.rstrip()}: {d}'
               for c, d in zip(classlist, difference) if float(d) != 0]

Output:

CLASS1: 25.2
CLASS2: 6.0
CLASS3: -5.0
CLASS5: -25.0
CLASS6: 6.0