Why in a simple loop I lose fetchAll's values of a sqlite3's table using python?

Question

I need to print some rows from an sqlite3's table using python3, but into the loop I get none value. following my code:

import sqlite3
db=sqlite3.connect('db.db')
cdb=db.cursor()
cdb.execute('create table if not exists table1 (field1,field2,field3)')
cdb.execute('insert into table1 values (?,?,?)',(1,2,3))
db.commit()
cdb.execute('insert into table1 values (?,?,?)',(4,5,6))
db.commit()
cdb.execute('insert into table1 values (?,?,?)',(1,7,8))
db.commit()
cdb.execute('select * from table1')
for i in range(len(cdb.fetchall())):
    if cdb.fetchone()[0]==1:print(cdb.fetchone())
db.close()

my error message:
AttributeError: 'NoneType' object has no attribute 'replace'

Thanks

Jan Wilamowski · Accepted Answer · 2021-10-07 07:41:11Z

1

Your call to cdb.fetchall() consumes the iterator and is pointless, so remove it:

for row in cdb.execute('select * from table1'):
    # do something with row

As described in the official documentation.

answered Oct 7, 2021 at 7:41

Jan Wilamowski

3,6672 gold badges13 silver badges24 bronze badges

Sign up to request clarification or add additional context in comments.

7 Comments

Tommy Over a year ago

sorry always same error message

Jan Wilamowski Over a year ago

@Tommy in which line does the error occur?

Jan Wilamowski Over a year ago

@Tommy that code occurs neither in your question nor in my answer. Have you tried implementing my suggestion?

Jan Wilamowski Over a year ago

@Tommy and then what do you inside the for loop? A simple print(row) would be a starting point.

Jan Wilamowski Over a year ago

@Tommy glad to hear that! Please consider marking the answer as accepted and/or upvoting to complete the Q/A cycle.

|

ELAi · Accepted Answer · 2021-10-07 10:43:21Z

1

After you fetchall the cursor point to nothing, so if you fetch anything it returns None.

to see what happend after commit the data just try:

cdb.execute('select * from table1')

print(cdb.fetchall()) # Return the data
print(cdb.fetchone()) # Return : None

db.close()

to fix this you could execute the sql again before the fetchone witch will be slow

I recommend doing this:

cdb.execute('select * from table1')

data = cdb.fetchall()
for i in data:
    if i[0] == 1: print(i)

db.close()

edited Oct 7, 2021 at 10:43

answered Oct 7, 2021 at 10:34

ELAi

1842 silver badges8 bronze badges

Collectives™ on Stack Overflow

Why in a simple loop I lose fetchAll's values of a sqlite3's table using python?

2 Answers 2

7 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

7 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related