TypeError: can't multiply sequence by non-int of type 'float' with sql query

I am trying to multiply sql result with an entry but i have this error :

Traceback (most recent call last):
  File "/usr/lib/python3.8/tkinter/__init__.py", line 1892, in __call__
    return self.func(*args)
  File "", line 92, in <lambda>
    command=lambda:[self.surface_result(),
  File "", line 189, in surface_result
    row = (cursor.fetchone() * (self.coef_entry / 100))
TypeError: can't multiply sequence by non-int of type 'float'

Here is my Entry code :

self.coef_entry = (Entry(app, width = 10))
self.coef_entry.grid(row=3, column=1, sticky=W)

self.coef_entry = int()

Here is my button code :

research_button = Button(app, text="Rechercher", 
                                    command=lambda:[self.surface_result(), 
                                                    self.eppaisseur_moy_result(), 
                                                    self.eppaisseur_hau_result(),
                                                    self.extrait_sec_moy_result(),
                                                    self.extrait_sec_bas_result(),
                                                    self.coef_melange_result()])
research_button.grid(row=4, column=0, padx=10, pady=10)

Here is my function where i got the error :

def surface_result(self):
        
    cursor.execute("""SELECT helicopter_surface_mouille FROM Helicopter WHERE helicopter_name=%s""",(self.programme_menu_deroulant.get(),))
    row = (cursor.fetchone() * (self.coef_entry / 100))
    for x in row:
        surface_result_label = Label(app, text=x, background = 'white', font=('arial', 12))
        surface_result_label.grid(row=5, column=1, sticky=W, padx=20)
    return row

My Table :

mycursor.execute(
    "CREATE TABLE Helicopter(\
        id_produitp INT NOT NULL,\
        id_helicopter INT AUTO_INCREMENT PRIMARY KEY,\
        helicopter_name VARCHAR(20) NOT NULL,\
        helicopter_surface_mouille INT(5) NOT NULL,\
        CONSTRAINT helicopter_ibfk_1 FOREIGN KEY(id_produitp)\
            REFERENCES ProduitP(id_produitp)\
        )"
)

If I run the function without the calculation, the query is working.

So how can I do this calculation with this sql syntax ?

Solution 1:

According to the documentation here the fetchone() function will either return a Tuple or None.

Either way the math operation will not do what you expect. Tuples can't be multiplied by floats and integer multiplication on a Tuple causes a repeat.

I would recommend checking if the row is None, then iterating over each value and doing the multiplication in the loop.

EDIT: In addition to the Tuple returned from fetchone(), there also may be another issue in the Entry code which stems from the use of the tk.Entry.

self.coef_entry = Entry(app, width = 10)
self.coef_entry.grid(row=3, column=1, sticky=W)

# coef is type tkinter.StringVar
self.coef = StringVar()
self.coef_entry['textvariable'] = self.coef

Then after the entry is retrieved from the user EDIT: note this code has been edited to use ‘self.coef.get()’

def surface_result(self):
        
    cursor.execute("""SELECT helicopter_surface_mouille FROM Helicopter WHERE helicopter_name=%s""",(self.programme_menu_deroulant.get(),))
    row = cursor.fetchone()
    # check if None was returned first 
    if not (row is None):
        for x in row:
            # do the math operation on the individual row values
            t = x * (float(self.coef.get()) / 100)
            surface_result_label = Label(app, text=t, background = 'white', font=('arial', 12))
            surface_result_label.grid(row=5, column=1, sticky=W, padx=20)
    return row

This may not entirely fix your issue since it depends on the order of execution. I would highly recommend reading tutorials on tkinter and how to structure tkinter programs with Python.