con = sqlite3.connect(db_path,isolation_level=None, detect_types=sqlite3.PARSE_DECLTYPES)
cur.execute('SELECT TIMESTAMPSTART,COUNT from COUNTING order by ROWID DESC limit 1;')
print(cur.fetchall())
last_d=cur.fetchall()
print(type(last_d))
print(len(last_d))
print(last_d[0])
此代码的结果如下:
[(datetime.datetime(2019, 4, 8, 21, 49, 5, 675964), 2)]
<type 'list'>
0
Traceback (most recent call last):
File "avg.py", line 70, in <module>
stream.statuses.filter(track='bitcoin')
File "/usr/lib/python2.7/site-packages/twython/streaming/types.py", line 67, in filter
self.streamer._request(url, 'POST', params=params)
File "/usr/lib/python2.7/site-packages/twython/streaming/api.py", line 154, in _request
if self.on_success(data): # pragma: no cover
File "avg.py", line 59, in on_success
update_counter()
File "avg.py", line 38, in update_counter
print(last_d[0])
IndexError: list index out of range
我的数据库如下所示:
CREATE TABLE COUNTING(
ID INTEGER PRIMARY KEY AUTOINCREMENT,
COUNT INT NOT NULL,
KEYWORD TEXT NOT NULL,
TIMESTAMPSTART TIMESTAMP NOT NULL,
TYPE TEXT NOT NULL
);
那么为什么它说列表的大小为 0,即使当我打印它时它有 2 个元素?我只是想从数据库中检索我的时间戳
那是因为您没有返回任何结果。请注意您的代码在下面的作用。你有:
print(cur.fetchall())
last_d=cur.fetchall()
print
语句获取所有行,不留下任何行供您实际设置 last_d
变量。根据此处,当没有可用行时,将返回空列表。您的 print
函数会消耗所有行,没有留下任何行供实际变量存储,因此为什么它返回它有一个长度0
。删除 print
语句,看看会发生什么。