问如何解决，PermissionError：[Errno 13]权限被拒绝：'test.from‘

EN

line 22, in <module>
    with open('test.from','a', encoding='utf8') as f:
PermissionError: [Errno 13] Permission denied: 'test.from'

import sqlite3
import pandas as pd

timeframes = ['2015-01']

for timeframe in timeframes:
    connection = sqlite3.connect('/Users/usr/Desktop/fileName/RC_{}.db'.format(timeframe))
    c = connection.cursor()
    limit = 5000
    last_unix = 0
    cur_length = limit
    counter = 0
    test_done = False

    while cur_length == limit:
        df = pd.read_sql("SELECT * FROM parent_reply WHERE unix > {} and parent NOT NULL and score > 0 ORDER BY unix ASC LIMIT {}".format(last_unix,limit),connection)
        last_unix = df.tail(1)['unix'].values[0]
        cur_length = len(df)

        if not test_done:
            with open('test.from','a', encoding='utf8') as f:
                for content in df['parent'].values:
                    f.write(content+'\n')
            with open('test.to','a', encoding='utf8') as f:
                for content in df['comment'].values:
                    f.write(str(content)+'\n')
            test_done = True