Python: pass list to another list but list is blank

I am using python 3.7 with openpyxl. I am attempting to parse data from a worksheet to a list. In this function Originally I was pulling info directly from one spreadsheet into a list and then using openpyxl to paste into another worksheet, however I am unable to use excel filters and such, so now I am attempting to edit the information in a list. The problem is that when I attempt to parse information to that list, it shows up fine in current_data, but as I append the list I get different information, almost as if it is overwriting the list. See the function and output below. Thank you in advance.

def cut_sheet_up(wsn, nws, output_log):
    x=0
    ws = wb[wsn]
    current_data = []
    for rowOfCellObjects in ws.iter_rows(min_row=0, min_col=0):
        current_data.clear()
        for cellObj in rowOfCellObjects:
            if cellObj.value is None:
                current_data.append('')
                # print causes ' value in front of string
            elif isinstance(cellObj.value, datetime) or isinstance(cellObj.value, time):
                current_data.append(cellObj.value)
            else:
                current_data.append(str(cellObj.value))
        nws.append(current_data)
        if wb[wsn] == wb['output_log']:
            x+=1
            print(current_data)
            output_log.append(current_data)
        else:
            pass

The first 150 lines or so are print as actual information under current_data, and the rest of the lines print as the following below.

['foo', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '']

In the worksheet I am passing the information to I receive correct data as well using the current function. However when I do a print(output_log) after the function I get all 1500 lines as

['foo', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '']

any help would be appreciated.

You're clearing the list inside the for loop, theres no need to reuse the same list here, so just initialize it within the for loop instead of clearing it

for rowOfCellObjects in ws.iter_rows(min_row=0, min_col=0):
    current_data = []

This is because you are re-using the same list in each iteration of the loop.

current_data.clear() does clear the list, but this is the same reference that got appended earlier.

To solve your problem, simply move the current_data = [] (line 4) inside the for loop and remove the current_data.clear() statement.

EDIT: Here's a short example to demonstrate the difference between a value and a reference.

my_list = []  # my_list is a variable that is pointing to a list
other_list = my_list  # other_list is a second variable that is pointing to the same list
my_list.append(1)
print(my_list)  # Prints out "[1]"
print(other_list)  # Also print out "[1]"

We say that both variables reference the same instance (the list). What happens if we assign a new list to my_list:

my_list = []
print(my_list)  # Prints out "[]"
print(other_list)  # Still prints out "[1]"

They now refer to different lists altogether.

Related to this is the concept of "pass by value" and "pass by reference", which you may find useful to know.