Occurrences using FOR and IF cycle

[fishhook]

1. Don't use range(len(a)), python cycle iterates over values, not indexes, just write

for item in a:

2. Your code works well

a = [100, 100, 50, 20, 100, 30]
x = 100
c = 0
for i in range(len(a)):
    if x == a[i]:
        c = c + 1

print(c)
>>> 3

3. Better code

a = [100, 100, 50, 20, 100, 30]
x = 100
c = sum(1 for i in a if i == x)

print(c)