How to store column value from mysql to python variable?

Question

actually i'm new to learning python and mysql database i have table named TABEL_NILAI in database like this:

id auto_increment primary key
NILAI_TRUST FLOAT
NAMA_ALAT VARCHAR(10)
--------------------------
|ID|NILAI_TRUST|NAMA_ALAT|
--------------------------
|1 | 0.12 | ALAT1 |
--------------------------
|2 | 0.34 | ALAT2 |
--------------------------
|3 | 0.54 | ALAT3 |
--------------------------

So i want to Retrieve value NILAI_TRUST from TABEL_NILAI and i want to do some math. here's code i was made:

kursor = db.cursor()
kursor.execute("SELECT NILAI_TRUST FROM TABEL_NILAI")
hasil = kursor.fetchall()
def hitung_standardeviasi():
 #input data
 TrustValue= x().split(',')
 for i in range(len(TrustValue)):
 TrustValue[i]= int(TrustValue[i])
 jumlah=0
 #Average
 for i in range(len(TrustValue))
 jumlah += TrustValue[i]
 ratarata = jumlah/len(TrustValue)
 total=0
 #sigma
 for i in range(len(TrustValue))
 hitung = (TrustValue[i]-ratarata)**2
 total += hitung
 sigma = total/(len(TrustValue)-1)
 #standardeviasi
 standardeviasi = math.sqrt(sigma)
 print(standardeviasi)
for x in hasil:
 hitung_standardeviasi()

And giving me error like:

Traceback (most recent call last):
 File "/home/lihat_tabel.py", line 60, in <module>
 hitung_standardeviasi()
 File "/home/lihat_tabel.py", line 24, in hitung_standardiviasi
 Trustvalue = x().split(',')
TypeError: 'tuple' object is not callable

so how to retrieve value into python variable in right ways. Please help:(

Answer 1

The query

kursor.execute("SELECT NILAI_TRUST FROM TABEL_NILAI")

will return a iterable of tuples, for example like this:

[(0.12,), (0.34,), (0.54,)]

So this line

TrustValue= x().split(',')

has two problems:

• x is a tuple, so it can't be called like x()
• x is not a string, so it doesn't have a split method

It looks like you want to make TrustValue a list of the int values of each result in the query. In that case this for loop is unnecessary, because it will only it will make the code operate on a single result at a time:

# You don't need this
for x in hasil:
 hitung_standardeviasi()

The hitung_standardeviasi function could begin like this:

def hitung_standardeviasi():
 #input data
 results = list(hasil)
 TrustValue= []
 for i in range(len(results)):
 TrustValue[i]= int(results[i][0])
 jumlah=0 

We can make this code a more readable by looping over the results directly instead of using the for i in range(len(collection)): idiom, which is often unnecessary in Python:

def hitung_standardeviasi():
 #input data
 TrustValue= []
 for (result,) in hasil:
 TrustValue.append(int(result))
 jumlah=0

Using a list comprehension is even more Pythonic:

def hitung_standardeviasi():
 #input data
 TrustValue = [int(result) for (result,) in hasil]
 jumlah=0 

You might want to look at the sum built-in function and the statistics module too.

• praanggi: thanks for your answer @snakecharmerb. but finally i used statistics modul for ending this problem.