Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
335 views
in Technique[技术] by (71.8m points)

python - About mysql cursor and iterator

Imagine I have a mysql cursor and data read. The amount of data might be very big that I want to deal with one line each time.

An easy and straight forward way might be like this:

while True:
    row = cursor.fetchone()
    if not row: break
    .....

But this doesn't look good, so I wonder whether this way works as imagined:

for row in iter(cursor.fetchall())

The thing I want to know is: if I use the iter(cursor.fetchall()) way, does it fetch all the data first or it just fetch one row at a time?

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

The MySQLdb cursor class implements the iterator protocol, so you can simply do this:

cursor.execute(sql)
for row in cursor:
    print row
    ...

Relevant code from MySQLdb.cursors.BaseCursor:

def __iter__(self):
    return iter(self.fetchone, None)

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...