TkInter ListBox and use of .format

Question 1

But .format will add the item then the column width.

format() does no such thing:

print "1234567890" * 2
print "{:4}{:4}{:4}{:4}".format('aaaa', 'bbbb', 'cccc', 'dddd')

--output:--
12345678901234567890
aaaabbbbccccdddd

The total width of the output is 16 = 4 x 4.

You should explicitly specify the alignment:

lb.insert(tk.END, "{:<5}-{:<2}".format(123, 9))

The docs say:

'<'   Forces the field to be left-aligned within the available space 
      (this is the default for most objects).

That 'most objects' language is what I think you may be running afoul of. Strings, numbers, etc. have a __format__() method that is called when they are asked to display themselves when you call the format() method on them. Check this out:

print "{:4}".format("a")
print "{:4}".format(9)

--output:--
a   
   9

Strings and numbers have different defaults for their justification. So I would not rely on the defaults--be explicit instead, and then you will know how the output will be justified.

Having said that, I have to use 17 for the min field width to actually get 10:

import Tkinter as tk

root = tk.Tk()
root.geometry("1000x200")

lb = tk.Listbox(root, width=150)
lb.insert("1", "{:4}{:4}".format("a", "b") )
lb.insert(tk.END, "1234567890" * 4)
lb.insert(tk.END, "{:<17}{:<10}".format(100, 200) )
lb.pack()

root.mainloop()

With that code, I see 200 starting in column 11. Okay, that alignment problem has to do with tkinter using a default font that is not fixed width, i.e. all characters do not occupy the same amount of space. If you are trying to align columns, you need to use a fixed width font. Try something like this:

import Tkinter as tk
import tkFont

root = tk.Tk()

my_font = tkFont.Font(family="Monaco", size=12)  #Must come after the previous line.

root.geometry("1000x200")

lb = tk.Listbox(root, width=150, font=my_font)
lb.insert("1", "{:4}{:4}".format("a", "b") )
lb.insert(tk.END, "1234567890" * 4)
lb.insert(tk.END, "{:>10}{:>10}".format(100, 200) )
lb.pack()

root.mainloop()

Question 2

Windows

listbox = Listbox(master, width=60, font='consolas')

I am on linux, where font='mono' works.