My code which adds fibonacci numbers to a list adds too many terms.

[DeaD_EyE]

Misunderstanding. You meant to have values in the list which are lower than 100.
My example creates a list with exactly 100 elements.

You compared j > 100, which is not the final value.
You've to compare (x[-1] + x[-2]) >= 100.

x = [0, 1]
for j in x:
    result = x[-1] + x[-2]
    if result >= 100:
        # stop is result is bigger or equal to 100
        break
    x.append(result)
print(x)

With my provided example:

from itertools import takewhile, islice


def fib():
    a, b = 0, 1
    while True:
        yield a
        a, b = a + b, a


def condition(value):
    return value < 100


generator = fib()
fibs_below_100 = list(takewhile(condition, generator))

And you can combine different functions from itertools.

Not bigger than 50 and maximum 10 elements:

fib_gen = fib()
fibs_below_50 = takewhile(lambda x: x < 100, fib_gen)
fibs_max_10_elements = islice(fibs_below_50 , 0, 10)

final_result = list(fibs_max_10_elements)

There is one big pitfall, if you use infinite generators:

[x for x in fib if x < 100]

This code will run until you get a MemoryError or hit CTRL+C.
There is no stop condition. Only the decision is made to take x or not.