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:(

snakecharmerb · Accepted Answer · 2019-12-14 12:00:05Z

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.

answered Dec 14, 2019 at 12:00

snakecharmerb

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1 Comment

praanggi Over a year ago

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

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