I have this code :
cur.execute("SELECT * FROM foo WHERE date=?",(date,))
for row in cur:
list_foo.append(row[2])
cur.execute("SELECT * FROM bar WHERE date=?",(date,))
for row in cur:
list_bar.append(row[2])
It works fine, but I’d like to automize this. I have made a list of the tables in my sqlite database, and I’d like something like this :
table_list = ['foo','bar']
for t in table_list:
cur.execute("SELECT * FROM "+t+" WHERE date=?",(date,))
for row in cur:
# and here I’d like to append to the list which name depends of t (list_foo, then list_bar, etc.)
But I don’t know how to do that. Any idea ?
Use a dictionary to collect your data. Don't try to set new local names for each list.
You could use string templating too, and a list comprehension to turn your result rows into lists:
data = {}
for t in table_list:
cur.execute("SELECT * FROM {} WHERE date=?".format(t), (date,))
data[t] = [row[2] for row in cur]
One caveat: only do this with a pre-defined list of table names; don't ever interpolate untrusted input like that without hefty escaping to prevent SQL injection attacks.
Related
I am currently trying to get a list of values from a table inside an SQL database. The problem is appending the values due to the table's name in which I can't change. The table's name is something like Value123/123.
I tried making a variable with the name like
x = 'Value123/123'
then doing
row.append(x)
but that just prints Value123/123 and not the values from the database
cursor = conn.cursor()
cursor.execute("select Test, Value123/123 from db")
Test = []
Value = []
Compiled_Dict = {}
for row in cursor:
Test.append(row.Test)
Value.append(row.Value123/123)
Compiled_Dict = {'Date&Time': Test}
Compiled_Dict['Value'] = Value
conn.close()
df = pd.DataFrame(Compiled_Dict)
The problem occurs in this line
Value.append(row.Value123/123)
When I run it I get that the database doens't have a table named 'Value123'. Since I think it's trying to divide 123 by 123? Unfortunately the table in the database is named like this and I cannot change it, so how do I pull the values from this table?
Edit:
cursor.execute("select Test, Value123/123 as newValue from db")
I tried this and it worked thanks for the solutions. Suggested by Yu Jiaao
I'm using PyMySQL to Update Data by iterating through table names , But the problem is that I was able to update the data from the first table only
the loop is not working after the first table
Ive tried using the fetchall() to get the table names and loop by that but it didnt work
def update():
global table_out
global i
cursor.execute("USE company;")
cursor.execute("SHOW TABLES;")
lst=[]
for table_name in cursor:
lst.append(table_name)
emp_list=lst[0][0]
print(emp_list)
i=0
while i<=len(lst)-1:
state="""SELECT `employee_name` from `%s` WHERE attended=0 """%(employees)
out=cursor.execute(state)
result=cursor.fetchall()
i+=1
for records in result:
table_out=''.join(records)
print(table_out)
db.commit()
try:
sql="""UPDATE `%s` SET `attended` = True WHERE `employee_name` = '%s' ;"""%(emp_list,table_out)
cursor.execute(sql)
I expect to iterate over all the tables in that database when this function is called
I'm not sure that your approach is quite optimal.
[In your middle block, employees is undefined - should that be emp_lst?]
Your select statement appears to reduce down to
SELECT employee_name FROM $TABLE WHERE attended=0;
which you then want to go through each table and change the value. Have you considered using the UPDATE verb instead? https://dev.mysql.com/doc/refman/8.0/en/update.html
UPDATE $table SET attended=True WHERE attended=0;
If that works for your desired outcome, then that will save you quite a few table scans and double handling.
So perhaps you could refactor your code along these lines:
def update_to_True():
# assume that cursor is a global
cursor.execute("USE company;")
tables = cursor.execute("SHOW TABLES;").fetchall()
for el in tables:
STMT="""UPDATE {0} SET attended=True WHERE attended=0;".format(el)
res = cursor.execute(el)
# for debugging....
print(res)
that's it!
I'm writing a script that formats a bunch of csv files into one csv file.
To do this, I'm using a couple of cursor tables in python via sqlite.
Here is my code - currently I'm just trying to get every row in gsap that is associated with a code that is in gsap_locs to print
data = c.execute("SELECT * from gsap_locs")
for row in data:
print row[0]
d2 = c.execute("select date, cardtype, volume, transactions from gsap where gsaploc=?", (row[0],))
for r2 in d2:
print r2
However, my code is only returning one row. I know that the problem isn't in the first for because when I take out everything after print row[0] it prints out all of the values from the first select.
Why is it escaping out of my first for after my second for runs without satisfying the conditions of the first for?
You are missing the fetchall or fetchone instructions.
It's a common thing, we think that the execute has done the job of getting the data but you should use fetch.
To retrieve data after executing a SELECT statement, you can either treat the cursor as an iterator, call the cursor’s fetchone() method to retrieve a single matching row, or call fetchall() to get a list of the matching rows.
import sqlite3
conn = sqlite3.connect('gasp.sqlite')
c = conn.cursor()
c.execute("SELECT * FROM gsap_locs")
rows = c.fetchall()
for row in rows:
print row[0]
c.execute("select * from gsap where loc=?", (row[0],))
d2 = c.fetchall()
for r2 in d2:
print r2
conn.close()
Looks like cursor.execute can only track one operation/returns an iterator at a time. You might want to keep the results of the first operation in memory, calling tuple on it:
data = tuple(c.execute("SELECT * from gsap_locs"))
for row in data:
...
Be sure to have enough memory to hold all the results from the first query.
I have recently encountered the problem of adding the elements of a database column. Here is the following code:
import sqlite3
con = sqlite3.connect("values.db")
cur = con.cursor()
cur.execute('SELECT objects FROM data WHERE firm = "sony"')
As you can see, I connect to the database (sql) and I tell to Python to select the column "objects".
The problem is that I do not know the appropriate command for summing the selected objects.
Any ideas/ advices are highly reccomended.
Thank you in advance!!
If you can, have the database do the sum, as that reduces data transfer and lets the database do what it's good at.
cur.execute("SELECT sum(objects) FROM data WHERE firm = 'sony'")
or, if you're really just looking for the total count of objects.
cur.execute("SELECT count(objects) FROM data WHERE firm = 'sony'")
either way, your result is simply:
count = cur.fetchall()[0][0]
Try the following line:
print sum([ row[0] for row in cur.fetchall()])
If you want the items instead adding them together:
print ([ row[0] for row in cur.fetchall()])
I have a table that has about 50 columns. To retrieve the variables from the table I am doing:
cursor.execute("SELECT * FROM title WHERE vendor_id = '%s'"%vendor_id)
data=cursor.fetchone()
provider, language, type, subtype, vendor_id = data[0], data[1], data[2], data[3], data[4]
etc...
Is there a way to do this more concisely: the variables I want to define are also the names of the columns. Perhaps something like (in pseudocode) --
values=cursor.fetchone; columns=cursor.fetchcolumns()
data = zip(columns, values)
select * is going to be particularly challenging here as you don't know what columns are being returned in which order. Depending on the database you're using and the wrapper you're using, you should be able to retrieve your rows as dicts instead which allows you to reference the columns as dict keys in the rows.
For instance, MySQLdb supports this through a DictCursor. See http://www.kitebird.com/articles/pydbapi.html
For other libraries, they should offer a similar feature.
You can use cursor.description and then convert the result to a dict:
import sqlite3
cnx = sqlite3.connect(r"g:\Python\Test\dabo\turnos\turnos.sqlite")
cur = cnx.execute("select * from Paciente")
rec = cur.fetchone()
fields = [i[0] for i in cur.description]
values = dict(zip(fields, rec))
print values["PacID"], values["PacNombre"] # ,...