In Python, the iteration variable in a ‘for’ loop is essentially a placeholder that references the current item in the sequence being iterated over. It’s not meant to be directly modified within the loop. Attempting to modify it won’t have the intended effect and can lead to unexpected behavior.

for i in bef:
...
            bef.remove(i)
...

demo code

string = """1,7,6,7,7,True,'a',9.8,'a',True"""
old = string.split(",")
new = []
for item in old:
    if item not in new:
        new.append(item)
old = list(map(eval, old))
new = list(map(eval, new))
print(old)
print(new)

[1, 7, 6, 7, 7, True, 'a', 9.8, 'a', True]
[1, 7, 6, True, 'a', 9.8]