How do I read cx_Oracle.LOB data in Python?

问题:

I have this code:

    dsn = cx_Oracle.makedsn(hostname, port, sid)
    orcl = cx_Oracle.connect(username + '/' + password + '@' + dsn)
    curs = orcl.cursor()
    sql = "select TEMPLATE from my_table where id ='6'"
    curs.execute(sql)
    rows = curs.fetchall()
    print rows
    template = rows[0][0]
    orcl.close()
    print template.read()

When I do print rows, I get this:

[(<cx_Oracle.LOB object at 0x0000000001D49990>,)]

However, when I do print template.read(), I get this error:

cx_Oracle.DatabaseError: Invalid handle!

Do how do I get and read this data? Thanks.

回答1:

I've found out that this happens in case when connection to Oracle is closed before the cx_Oracle.LOB.read() method is used.

orcl = cx_Oracle.connect(usrpass+'@'+dbase)
c = orcl.cursor()
c.execute(sq)
dane =  c.fetchall()

orcl.close() # before reading LOB to str

wkt = dane[0][0].read()

And I get: DatabaseError: Invalid handle!
But the following code works:

orcl = cx_Oracle.connect(usrpass+'@'+dbase)
c = orcl.cursor()
c.execute(sq)
dane =  c.fetchall()

wkt = dane[0][0].read()

orcl.close() # after reading LOB to str

回答2:

Figured it out. I have to do something like this:

curs.execute(sql)        
for row in curs:
    print row[0].read()

回答3:

You basically have to loop through the fetchall object

dsn = cx_Oracle.makedsn(hostname, port, sid)
orcl = cx_Oracle.connect(username + '/' + password + '@' + dsn)
curs = orcl.cursor()
sql = "select TEMPLATE from my_table where id ='6'"
curs.execute(sql)
rows = curs.fetchall()
for x in rows:
   list_ = list(x)
   print(list_)