This is a really robust self-created script that partitions CSV files contingent on user input so let's get to using it shall we?

Split_CSV_Files.py

import argparse
import csv
import os

# Function to calculate total rows in CSV
def get_total_rows(csv_file):
    with open(csv_file, 'r') as f:
        return sum(1 for row in csv.reader(f)) - 1  # Exclude header

# Function to split CSV files
def split_csv(input_file, row_limit, output_dir=None):
    total_rows = get_total_rows(input_file)
    
    # Error checking for row_limit
    is_percentage = row_limit.endswith('p')
    if is_percentage:
        percentage = int(row_limit.rstrip('p'))
        if percentage > 100:
            print("Error: Percentage cannot exceed 100%")
            return
        row_limit = int((percentage / 100) * total_rows)
    else:
        row_limit = int(row_limit)
    
    if row_limit > total_rows:
        print(f"Error: Number of rows specified ({row_limit}) exceeds total number of rows ({total_rows})")
        return

    with open(input_file, 'r') as f:
        csvreader = csv.reader(f)
        headers = next(csvreader)

        # Initialize variables
        output_file_count = 0
        rows_written = 0
        current_output = None
        csvwriter = None
        remaining_rows = total_rows

        while remaining_rows > 0:
            current_limit = min(row_limit, remaining_rows)
            if current_output:
                current_output.close()
                
            output_file_count += 1
            output_file_name = f"{os.path.splitext(os.path.basename(input_file))[0]}_part{output_file_count}.csv"
            output_file_path = os.path.join(output_dir, output_file_name) if output_dir else f"{input_file}_part{output_file_count}.csv"
            current_output = open(output_file_path, 'w', newline='')
            csvwriter = csv.writer(current_output)
            csvwriter.writerow(headers)
            
            for _ in range(current_limit):
                try:
                    row = next(csvreader)
                    csvwriter.writerow(row)
                    rows_written += 1
                except StopIteration:
                    break
            
            remaining_rows -= current_limit

        if current_output:
            current_output.close()

if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Split a large CSV file into smaller CSV files.')
    
    # Input CSV file
    parser.add_argument('-i', '--input', type=str, help='Path to the large CSV file that needs to be split.')
    
    # Row limit for each smaller CSV file
    parser.add_argument('-r', '--rows', type=str, help='Number or percentage of rows in each smaller CSV file.')
    
    # Output directory
    parser.add_argument('-o', '--output', type=str, help='Output directory for smaller CSV files.')
    
    args = parser.parse_args()
    
    if args.input:
        input_file = args.input
    else:
        input_file = input("Enter the name or full path of the CSV file: ")
    
    if args.rows:
        row_limit = args.rows
    else:
        row_limit = input("Enter the number of rows or percentage (e.g., 100 or 20p) for each partition: ")
    
    split_csv(input_file, row_limit, args.output)