Creating a variables inside FOR loop

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Creating a variables inside FOR loop - zazas321 - Sep-11-2020

Hello. I would like to know what is really the most efficient and best way to create multiple variables inside for loop. At the moment, I am creating 20 variables one by one and that is not a massive problem for me. See the code below:

def picking_gui():
    number=count_unique_devices(myConnection)
    print("number=",number)
    global device1,device2,device3,device4,device5,device6,device7,device8,device9,device10,device11,device12,device13,device14,device15,device16,device17,device18,device19,device20
    #global canvas_tk
    device1 = canvas_tk.create_rectangle(20,400,90,470,fill='red')
    canvas_tk.create_text(55,435,text="device1")
    device2 = canvas_tk.create_rectangle(110,400,180,470,fill='red')
    canvas_tk.create_text(145,435,text="device2")
    device3 = canvas_tk.create_rectangle(210,400,280,470,fill='red')
    canvas_tk.create_text(245,435,text="device3")
    device4 = canvas_tk.create_rectangle(310,400,380,470,fill='red')
    canvas_tk.create_text(345,435,text="device4")
    device5 = canvas_tk.create_rectangle(410,400,480,470,fill='red')
    canvas_tk.create_text(445,435,text="device5")
    device6 = canvas_tk.create_rectangle(510,400,580,470,fill='red')
    canvas_tk.create_text(545,435,text="device6")
    device7 = canvas_tk.create_rectangle(610,400,680,470,fill='red')
    canvas_tk.create_text(645,435,text="device7")
    device8 = canvas_tk.create_rectangle(710,400,780,470,fill='red')
    canvas_tk.create_text(745,435,text="device8")
    device9 = canvas_tk.create_rectangle(810,400,880,470,fill='red')
    canvas_tk.create_text(845,435,text="device9")
    device10 = canvas_tk.create_rectangle(910,400,980,470,fill='red')
    canvas_tk.create_text(945,435,text="device10")
    device11 = canvas_tk.create_rectangle(20,500,90,570,fill='red')
    canvas_tk.create_text(55,535,text="device11")
    device12 = canvas_tk.create_rectangle(110,500,180,570,fill='red')
    canvas_tk.create_text(145,535,text="device12")
    device13 = canvas_tk.create_rectangle(210,500,280,570,fill='red')
    canvas_tk.create_text(245,535,text="device13")
    device14 = canvas_tk.create_rectangle(310,500,380,570,fill='red')
    canvas_tk.create_text(345,535,text="device14")
    device15 = canvas_tk.create_rectangle(410,500,480,570,fill='red')
    canvas_tk.create_text(445,535,text="device15")
    device16 = canvas_tk.create_rectangle(510,500,580,570,fill='red')
    canvas_tk.create_text(545,535,text="device16")
    device17 = canvas_tk.create_rectangle(610,500,680,570,fill='red')
    canvas_tk.create_text(645,535,text="device17")
    device18 = canvas_tk.create_rectangle(710,500,780,570,fill='red')
    canvas_tk.create_text(745,535,text="device18")
    device19 = canvas_tk.create_rectangle(810,500,880,570,fill='red')
    canvas_tk.create_text(845,535,text="device19")
    device20 = canvas_tk.create_rectangle(910,500,980,570,fill='red')
    canvas_tk.create_text(945,535,text="device20")

I am creating 20 rectangles and assigning a different name to each one. The reason why I am assigning a name to each rectangle and declaring it as global, is because I need to be able to access and modify these rectangles in other functions such as:

def update_rectangle_color(device_name,last_device):
    canvas_tk.itemconfig(eval(last_device),fill="red")
    print("updating rectangle colour=",device_name)
    canvas_tk.itemconfig(eval(device_name),fill="green")
    print("item updated")
    last_device = device_name
    return last_device

in the function above, I pass the device name, for example "device4" and I will change the colour of that rectangle.

My code works fine and as expected, the problem is that everytime the program starts, I calculate how many unique devices I have ( it might be 5, 10, 15 or whatever) and I want to generate the number of rectangles based on the number that has been returned from the function:

number=count_unique_devices(myConnection)
    print("number=",number)

I am thinking whether I could use a for loop or simmilar to dynamically create and initialze only the required amount of rectangle everytime?

RE: Creating a variables inside FOR loop - bowlofred - Sep-11-2020

Don't create 20 different variables. Create one variable that can hold 20 objects (a list or a dictionary)

RE: Creating a variables inside FOR loop - buran - Sep-11-2020

also, in addition to @bowlofred's excellent advise - don't use globals. Make GUI using OOP approach (i.e. with class)

RE: Creating a variables inside FOR loop - zazas321 - Sep-11-2020

Thanks everyone, I have managed to create variables using for loop with dictionaries as bowlofred mentioned:

def picking_gui():
    number=count_unique_devices(myConnection)
    print("number=",number)
    global devices
    devices = {}
    for x in range(1,number):
        devices["device{0}".format(x)] = canvas_tk.create_rectangle(20+(x*90),400,90+(x*90),470,fill='red')
        name_text = "device"+str(x)
        canvas_tk.create_text(55+(x*90),435,text=name_text)
        if(x>10):
            devices["device{10}".format(x)] = canvas_tk.create_rectangle(20+(x*90),500,90+(x*90),570,fill='red')

I now will have a look at how to create my GUI using OOP aproach as I have never used it before. It seems more complex than the usual program flow I am used to

RE: Creating a variables inside FOR loop - Naheed - Sep-11-2020

i suggest you to use the zip function as well. It will help declare multiple tuples in a single for loop sentence.

RE: Creating a variables inside FOR loop - Naheed - Sep-16-2020

(Sep-11-2020, 06:30 AM)bowlofred Wrote: Don't create 20 different variables. Create one variable that can hold 20 objects (a list or a dictionary)

Yes agreed with you. We have to create variable with different objects and this way, our code will be managed very easily.