flake8-tkinter 0.5.0

Flake8 plugin to detect (too) common mistakes and bad practices in Tkinter projects

flake8-tkinter

Flake8 plugin to detect (too) common mistakes and bad practices in Tkinter projects

Installation

pip install flake8-tkinter

List of warnings

TK102

Don't call mainloop multiple times, as it's totally unnecessary

def func():
    top = tk.Toplevel()
-   top.mainloop()
root.mainloop()

TK111

Calling a function instead of passing the reference for command argument

- ttk.Button(command=foo())
+ ttk.Button(command=foo)

TK112

Calling a function with arguments instead of using a lambda or a partial function and passing the reference for command argument

- ttk.Button(command=foo(bar, baz))
+ ttk.Button(command=lambda: foo(bar, baz))

TK131

Don't assign to w.grid() / w.pack() / w.place(), it's return value is None

- btn = ttk.Button().grid()
+ btn = ttk.Button()
+ btn.grid()

TK201

Don't use from tkinter import *

- from tkinter import *
+ import tkinter
# OR
+ import tkinter as tk

TK202

Don't use from tkinter.ttk import *

- from tkinter.ttk import *
+ from tkinter import ttk

TK211

import tkinter.ttk as ttk is pointless

- import tkinter.ttk as ttk
+ from tkinter import ttk

TK221

Don't use dumb tkinter constants, use booleans instead

- w.pack(expand=tk.TRUE)
+ w.pack(expand=True)

- w.pack(expand=tk.FALSE)
+ w.pack(expand=False)

- w.pack(expand=tk.YES)
+ w.pack(expand=True)

- w.pack(expand=tk.NO)
+ w.pack(expand=False)

- w.pack(expand=tk.ON)
+ w.pack(expand=True)

- w.pack(expand=tk.OFF)
+ w.pack(expand=False)

TK231

Use add=True or explicit add=False in bindings

- w.bind("<Button-1>, foo)
+ w.bind("<Button-1>, foo, add=True)
# OR
+ w.bind("<Button-1>, foo, add=False)

TK232

Creating tag bindings in a loop can lead to memory leaks, because the created Tcl commands won't be cleaned up when deleting the tag

for index, foo in enumerate(foos):
-   w.tag_bind(f"bar_{index}", "<Button-1>, baz)
+   tcl_command = w.tag_bind(f"bar_{index}", "<Button-1>, baz)
+   bindings.append(tcl_command)  # Clean them up later with `.deletecommand()`

TK304

Don't use things like add="+". Use a boolean instead

- w.bind("<Button-1>, foo, add="+")
+ w.bind("<Button-1>, foo, add=True)

More planned warnings

• Common mistakes

  • Warn when assigning to result of w.pack() | w.grid() | w.place() call (None) (TK131)
  • Warn when using more than oneTk instance: child windows must be created from Toplevel class (TK101)
  • Warn when using more than one mainloop() call (TK102)
  • Suggest using w.after(ms) instead of time.sleep(s) (TK121)
  • Suggest keeping reference of local PhotoImage instance to avoid GC (TK141)
  • Suggest refactoring code that uses w.update, as it's usually pointless, potentially harmful, and considered a code smell (TK103)
  • Warn when using a float as Text widget index (TK132)
  • Infinite loop in a handler - propose to use recursive function with w.after (TK122)
  • Warn when calling the function inline, instead of just referencing it (TK111)
  • Suggest using a lambda function when args are passed to inline calls (TK112)

• Common best practices

  • Warn on from tkinter import *, suggest using import tkinter or import tkinter as tk instead (TK201)
  • Warn on from tkinter.ttk import *, suggest using from tkinter import ttk instead (TK202)
  • Warn on import tkinter.ttk as ttk, as from tkinter import ttk is simpler (TK211)
  • Suggest changing tk.TRUE and tk.FALSE to True and False, as there's really no reason for using these constants instead of booleans (TK221)
  • Suggest using tk.NSEW instead of tk.N+tk.S+tk.E+tk.W, and other combinations (TK222)
  • A widget is created without a parent container specified, and there is a container in the same scope (tk.Toplevel or tk.Frame), or the widget is created in a method a subclass of tk.Tk, tk.Toplevel or tk.Frame (TK232)
  • Warn when a huge app isn't OO (?)
  • Warn when not using add=True or explicit add=False in bindings (TK231)
  • Warn when using tag_bind inside a loop, but not storing the Tcl command (can cause memory leaks later) (TK232)

• Opinionated suggestions

  • Suggest changing things like root.wm_title() to root.title() (tho I use wm_attributes quite often, probably that should be an exception) (TK305)
  • Warn when calling mainloop() on something other than the root window (TK303)
  • Suggest using more clear binding sequences, like <Button-1> instead of <1> and <Key-a> instead of <a> (TK301)
  • Warn if a parent is not specified (?) (TK306)
  • Prefer to use more readable widget.config(property=value) instead of widget["property"] = value (TK302)
  • Suggest changing tkinter constants to string literals (this option should be disabled by default) (TK307)
  • Warn when using add="+" in bindings, use a boolean instead (TK304)

Development

1. Clone the repo
2. Set up a virtual environment, activate, and install flake8 and pytest in it
3. Run pip install -e . to install flake8-tkinter in editable format
4. Run python3 -m pytest to test your changes

Credits

The idea of this project is by @insolor