Python and openpyxl is running slowly

Question

I am trying to process a 10,000+ line spreadsheet, and even when I narrow it to ~3,000 lines, Python is running slowly (about 1 line per second). I'm comparing each entry in the third column; if I find a match, I check the value in the fifth column. If both match, I have an interesting record.

I know this is probably something simple, or that there's an easier, more pythonic way, but am suffering from coder's block.

I'm using python 3.8 and openpyxl 3.0.0 under Windows 10. Here's the code:

---

#! python3
''' Copy specific rows from a spreadsheet and write them to a
    temporary spreadsheet.
    Most of this was copied from
    https://stackoverflow.com/questions/44593705/
    how-to-copy-over-an-excel-sheet-to-another-workbook-in-python'''

import logging  
import os  
import tkinter as tk  
from tkinter import filedialog  

import openpyxl  
from openpyxl.utils import column_index_from_string, get_column_letter

logging.basicConfig(level=logging.DEBUG, \
                    format=' %(asctime)s - %(levelname)s- %(message)s')  
logging.disable(logging.DEBUG)  
logging.info('=== STARTING ===')  

root = tk.Tk()  
root.withdraw()    # Hide the Tk window.  

# Get the source spreadsheet.
src_file = filedialog.askopenfilename()  
logging.debug(src_file)  
src_file_path = os.path.split(src_file)  
logging.debug('Path = ' + src_file_path[0] + '; File = ' + src_file_path[1])  

# Open the source spreadsheet.  
src_wb = openpyxl.load_workbook(src_file, read_only=True)  
src_ws = src_wb.worksheets[0]  

# CONSTANTS  
KEYDATE_TARGET = "PM's ESTIM."  
MANAGER_TARGET = '055'  
SRC_CONTRACT_COL = 'D'  
SRC_PROJ_COL = 'F'  
SRC_KEYDATE_COL = 'E'  
SRC_MAX_ROWS = src_ws.max_row  
SRC_MGR_COL = 'C'  
SRC_SUBJ_COL = 'J'  

# Initializations  
src_row_num = 7274  
temp_row_num = 0  

src_col = 3  
for src_row in src_ws.iter_rows(min_row=src_row_num, max_row = 9001):  
    # Build cell coordinates  
    src_row_num += 1  
    src_cell_coord = SRC_MGR_COL + str(src_row_num)  
    logging.debug(src_cell_coord)  
    src_cell = src_ws[src_cell_coord]  
    if src_cell.value == MANAGER_TARGET or src_cell.value == '053':  
        logging.info('Found manager ' + str(src_cell.value))  
        # Save row number  
        mgr_row = src_cell.row  
        keydate_coord = SRC_KEYDATE_COL + str(mgr_row)  
        keydate_cell = src_ws[keydate_coord]  
        if KEYDATE_TARGET in keydate_cell.value:  
            logging.info('keydate_coord = ' + str(keydate_coord))  

logging.info('=== DONE ===')