Use loop to create variables python 3

Question

Intro: I am using the tkinter module to create two windows, each as separate classes. I want to take the integer entered on the first window, and use it to create that number of labels and entries in the second window.

i.e.

import tkinter

class FirstWindow:
    def __init__(self):
        self.firstMaster = tkinter.Tk()
        self.topFrame = tkinter.Frame(self.numberMaster)
        ...
        self.numEntry = tkinter.Entry(self.topFrame, width=10)
        ...
        self.averageButton = tkinter.Button(self.bottomFrame, text='next', command=self.nextstep)
        ...
        ...
        tkinter.mainloop()

    def nextStep(self):
        self.numberItems = int(self.numEntry.get())
        self.average = AveragerGUI(self.numberTests)

class AveragerGUI:
    def __init__(self, numTests):
        self.secondMaster = tkinter.Tk()
        self.topFrame = tkinter.Frame(self.secondMaster)

        for number in range(1, numTests):
            self.frame'number' = tkinter.Frame(self.secondMaster)

I know that this will not work; I included it just to illustrate what I want to do: create a number of frames dependent on the numTests parameter.

I thought of using a list, but this is a problem because I do not know how to convert the strings into the names of variables:

varList = []
for number in range(1, numberTests):
    label = str(number)
    var = 'Frame' + label
    varList.append(var)

Any thoughts?

Martijn Pieters · Accepted Answer · 2013-04-18 15:53:35Z

1

If you use a list, there is no need to generate names:

self.frames = []
for number in range(numTests):
    self.frames.append(tkinter.Frame(self.secondMaster))

You can simplify that by using a list comprehension:

self.frames = [tkinter.Frame(self.secondMaster) for _ in in range(numTests)]

Now you can access each frame by index:

self.frames[0]
self.frames[1]

or loop through them:

for frame in self.frames:
    # do something with frame

answered Apr 18, 2013 at 15:53

Martijn Pieters

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1 Comment

kindall Over a year ago

Yes. If you are thinking about creating an arbitrary number of variables, you are almost always better served by a container of some sort, such a list or a dictionary.

spencerlyon2 · Accepted Answer · 2013-04-18 16:03:37Z

0

Although I aggree with @Martijn Pieters, if you really did want to name variables inside a loop, the easiest way I have found to do this is to use the builtin exec function.

As an example, if I wanted to make x0, x1, x2, x3 equal the first 4 items of a list I would do the following:

>>>the_list = [1, 3.4, 'g', sum]

>>> for i in range(len(the_list)):
...    exec('x%i = the_list[%i]' % (i, i))

>>> print(x0)
1 
>>> print(x1)
3.4
>>> print(x2)
g
>>> print(x3)
<built-in function sum>

answered Apr 18, 2013 at 16:03

spencerlyon2

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