FeatureNotSupported: COPY from a file is not supported

I am looking to find a faster solution than pandas to_sql to ingest a pandas df into postgres database.

import time
import psycopg2

df = pd.read_csv('upload_test_data.csv') 
conn = psycopg2.connect(user=username,password=password,
                        host=host,port=port,database=db)
cursor = conn.cursor()

#perform COPY test and print result
sql = '''
    COPY copy_test
    FROM 'C:\\Users\\Documents\\copy_test.csv'
    DELIMITER ',' CSV;
    '''

table_create_sql = '''
CREATE TABLE IF NOT EXISTS copy_test (id                bigint,
                                      quantity          int,
                                      cost              double precision,
                                      total_revenue     double precision)
                    '''

cursor.execute(table_create_sql)
cursor.execute('TRUNCATE TABLE copy_test') 

start_time = time.time()
df.to_csv('upload_test_data_from_copy.csv', index=False, header=False) 

cursor.execute(sql)
conn.commit()
cursor.close()
print("COPY duration: {} seconds".format(time.time() - start_time))

The code above returns an error:

FeatureNotSupported: COPY from a file is not supported

As the goal is to automate the process, I prefer that the solution is fully in Python to switching between different software.

Version: PostgreSQL 13.7 on x86_64-pc-linux-gnu