Python in Jupyter Notebook: .append kept adding without refresh the list in each run

Please help with append() in a loop that behaves weird as shown below.

I have a string.

1. I extract alphabet letters from the string and store to a list, called ltr.
2. I specify the conditions for each element of the ltr list
3. I stored the boolean result in a list, called ltr_spec
4. It looks fine for the first run if I purposely run ltr_spec = [] in another cell of Jupyter Notebook to initialize ltr_spec.
5. However, if I run the cell again, ltr_spec keep adding new elements without being refreshed as an empty list which was define at the beginning of the code.
6. Note that the first append() in ltr.append() behaves as expected. But the second append() in ltr_spec.append() behaves unexpected when run the cell in Jupyter Notebook.

Would you please kindly tell me if it is the issue of the loop, or append(), or Jupyter Notebook?

Sample code below.

s ='Qm1p4Q7p5d2'
ltr = []
# Test if each element of 'ltr' satisfies the spec of alphabet letter in a string
ltr_j = False
ltr_spc = []

for i in s:
    if i.isalpha():
        ltr.append(i)
# Utilize the modulo operation, a math concept, to locate the position of the letters
if (len(ltr) % 3 == 0):
    for j in range(len(ltr)):
        # Test ltr list on the specs of index, letter, and upper/lower case
        if ((j % 3 == 0 and ltr[j] == "Q") or
                # Ask if there is a better way to write j %in% c(1,2) (R's match function) without using Numpy!
            (j % 3 == 1 and ((ltr[j] == "d" and ltr[j+1] == "p") or (ltr[j] == "p" and ltr[j+1] == "d"))) or
                # Ask if the following condition is redundant given the condition specified above is already checked..
            (j % 3 == 2 and ((ltr[j] == "d" and ltr[j-1] == "p") or (ltr[j] == "p" and ltr[j-1] == "d")))):
                ltr_j = True
        else:
            ltr_j = False
        ltr_spec.append(ltr_j)

Output in first run:

ltr
['Q', 'm', 'p', 'Q', 'p', 'd']
ltr_spec
[True, False, False, True, True, True]

Output in second run:

ltr
['Q', 'm', 'p', 'Q', 'p', 'd']
ltr_spec
[True, False, False, True, True, True, True, False, False, True, True, True]

Output in third run:

ltr
['Q', 'm', 'p', 'Q', 'p', 'd']
ltr_spec
[True,
 False,
 False,
 True,
 True,
 True,
 True,
 False,
 False,
 True,
 True,
 True,
 True,
 False,
 False,
 True,
 True,
 True]

You have defined ltr_spc = [] but at the bottom you call ltr_spec.append(ltr_j), so the list is not emptied.

Here is the code after correct ltr_spc = [] to ltr_spec = [], and it gives consistent output after re-run many times.