How to pass arguments to a Button command in Tkinter

Question

Suppose I have the following Button made with Tkinter in Python   import Tkinter as Tk win   Tk Toplevel   frame   Tk Frame master win  grid row 1  column 1  button   Tk Button master frame  text  press   command action    The method action is called when I press the button  but what if I wanted to pass some arguments to the method action   I have tried with the following code    button   Tk Button master frame  text  press   command action someNumber     This just invokes the method immediately  and pressing the button does nothing

User · Answer

Use lambda  import tkinter as tk  root   tk Tk   def go text       print text   b   tk Button root  text  Click   command lambda  go  hello    b pack   root mainloop     output   hello

User · Answer

JasonPy - a few things      if you stick a button in a loop it will be created over and over and over again    which is probably not what you want   maybe it is      The reason it always gets the last index is lambda events run when you click them - not when the program starts  I m not sure 100  what you are doing but maybe try storing the value when it s made then call it later with the lambda button    eg   don t use this code  just an example   for entry in stuff that is happening      value store entry    stuff that is happening   then you can say      button    command  lambda  value store 1    hope this helps

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Python s ability to provide default values for function arguments gives us a way out   def fce x myX  y myY       myFunction x y  button   Tk Button mainWin  text  press   command fce    See  http   infohost nmt edu tcc help pubs tkinter web extra-args html  For more buttons you can create a function which returns a function   def fce myX  myY       def wrapper x myX  y myY           pass         pass         pass         return x y     return wrapper  button1   Tk Button mainWin  text  press 1   command fce 1 2   button2   Tk Button mainWin  text  press 2   command fce 3 4   button3   Tk Button mainWin  text  press 3   command fce 9 8

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button   Tk Button master frame  text  press   command lambda  action someNumber     I believe should fix this

User · Answer

The reason it invokes the method immediately and pressing the button does nothing is that action somenumber  is evaluated and its return value is attributed as the command for the button  So if action prints something to tell you it has run and returns None  you just run action to evaluate its return value and given None as the command for the button   To have buttons to call functions with different arguments you can use global variables  although I can t recommend it   import Tkinter as Tk  frame   Tk Frame width 5  height 2  bd 1  relief Tk SUNKEN  frame grid row 2 column 2  frame pack fill Tk X  padx 5  pady 5  def action        global output     global variable     output insert Tk END variable get    button   Tk Button master frame  text  press   command action  button pack   variable   Tk Entry master frame  variable pack   output   Tk Text master frame  output pack    if   name         main         Tk mainloop     What I would do is make a class whose objects would contain every variable required and methods to change those as needed   import Tkinter as Tk class Window      def   init   self           self frame   Tk Frame width 5  height 2  bd 1  relief Tk SUNKEN          self frame grid row 2 column 2          self frame pack fill Tk X  padx 5  pady 5           self button   Tk Button master self frame  text  press   command self action          self button pack            self variable   Tk Entry master self frame          self variable pack            self output   Tk Text master self frame          self output pack        def action self           self output insert Tk END self variable get     if   name         main         window   Window       Tk mainloop

User · Answer

Lambdas are all well and good  but you can also try this  which works in a for loop btw    root   Tk    dct     1     args    2     args   def keypress event        args   dct event char      for arg in args          pass for i in range 10       root bind str i   keypress    This works because when the binding is set  a key press passes the event as an argument  You can then call attributes off the event like event char to get  1  or  UP  ect  If you need an argument or multiple arguments other than the event attributes  just create a dictionary to store them

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I am extremely late  but here is a very simple way of accomplishing it   import tkinter as tk def function1 param1  param2       print str param1    str param2    var1    Hello   var2    World   def function2        function1 var1  var2   root   tk Tk    myButton   tk Button root  text  Button   command function2  root mainloop     You simply wrap the function you want to use in another function and call the second function on the button press

User · Answer

The best thing to do is use lambda as follows   button   Tk Button master frame  text  press   command lambda  action someNumber

User · Answer

You need to use lambda   button   Tk Button master frame  text  press   command lambda  action someNumber

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Just to make the answer of Nae a little bit more elaborate  here is a full blown example which includes the possibility to pass a variable to the callback which contains different values for each button  import tkinter as tk      def callback text       print text   top   tk Tk   Texts   quot text1 quot    quot text2 quot    quot text3 quot   Buttons     for i  z in enumerate Texts       Buttons append tk Button top  text z  command  lambda ztemp z   callback ztemp        Buttons i  pack side tk LEFT  padx 5   top mainloop    By defining a temporary variable ztemp  the value of that variable gets fixed at the moment when the button is defined

User · Answer

One simple way would be to configure button with lambda like the following syntax   button  command     lambda arg1   local var1  arg2   local var2   function arg1  arg2

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Building on Matt Thompsons answer   a class can be made callable so it can be used instead of a function   import tkinter as tk  class Callback      def   init   self  func   args    kwargs           self func   func         self args   args         self kwargs   kwargs     def   call   self           self func  self args    self kwargs   def default callback t       print  Button      pressed   format t    root   tk Tk    buttons     A    B    C    for i  b in enumerate buttons       tk Button root  text b  command Callback default callback  b   grid row i  column 0   tk mainloop

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Example GUI   Let s say I have the GUI   import tkinter as tk  root   tk Tk    btn   tk Button root  text  Press   btn pack    root mainloop     What Happens When a Button Is Pressed  See that when btn is pressed it calls its own function which is very similar to button press handle in the following example   def button press handle callback None       if callback          callback     Where exactly the method assigned to btn  command   is being callled   with   button press handle btn  command      You can simply think that command option should be set as  the reference to the method we want to be called  similar to callback in button press handle     Calling a Method Callback  When the Button is Pressed  Without arguments   So if I wanted to print something when the button is pressed I would need to set   btn  command     print   default to print is new line   Pay close attention to the lack of    with the print method which is omitted in the meaning that   This is the method s name which I want you to call when pressed but don t call it just this very instant   However  I didn t pass any arguments for the print so it printed whatever it prints when called without arguments   With Argument s   Now If I wanted to also pass arguments to the method I want to be called when the button is pressed I could make use of the anonymous functions  which can be created with lambda statement  in this case for print built-in method  like the following   btn  command     lambda arg1  Hello   arg2      arg3  World     print arg1   arg2   arg3      Calling Multiple Methods when the Button Is Pressed  Without Arguments  You can also achieve that using lambda statement but it is considered bad practice and thus I won t include it here  The good practice is to define a separate method  multiple methods  that calls the methods wanted and then set it as the callback to the button press   def multiple methods        print  Vicariously     the first inner callback     print  I     another inner callback   With Argument s   In order to pass argument s  to method that calls other methods  again make use of lambda statement  but first   def multiple methods  args    kwargs       print args 0     the first inner callback     print kwargs  opt1      another inner callback   and then set   btn  command     lambda arg  live   kw  as the    a new method arg  opt1 kw      Returning Object s  From the Callback  Also further note that callback can t really return because it s only called inside button press handle with callback   as opposed to return callback    It does return but not anywhere outside that function  Thus you should rather modify object s  that are accessible in the current scope     Complete Example with global Object Modification s   Below example will call a method that changes btn s text each time the button is pressed   import tkinter as tk  i   0 def text mod        global i  btn             btn can be omitted but not sure if should be     txt     Vicariously    I    live    as    the    whole    world    dies       btn  text     txt i       the global object that is modified     i    i   1    len txt     another global object that gets modified  root   tk Tk    btn   tk Button root  text  My Button   btn  command     text mod  btn pack fill  both   expand True   root mainloop       Mirror

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Use a lambda to pass the entry data to the command function if you have more actions to carry out  like this  I ve tried to make it generic  so just adapt    event1   Entry master  button1   Button master  text  OK   command lambda  test event event1 get      def test event event text       if not event text          print  Nothing entered       else          print str event text              do stuff   This will pass the information in the event to the button function  There may be more Pythonesque ways of writing this  but it works for me

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For posterity  you can also use classes to achieve something similar  For instance   class Function Wrapper        def   init   self  x  y  z           self x  self y  self z   x  y  z     def func self           return self x   self y   self z   execute function   Button can then be simply created by   instance1   Function Wrapper x  y  z  button1    Button master  text    press   command   instance1 func    This approach also allows you to change the function arguments by i e  setting instance1 x   3

User · Answer

I personally prefer to use lambdas in such a scenario  because imo it s clearer and simpler and also doesn t force you to write lots of wrapper methods if you don t have control over the called method  but that s certainly a matter of taste   That s how you d do it with a lambda  note there s also some implementation of currying in the functional module  so you can use that too    button   Tk Button master frame  text  press   command  lambda  action someNumber

User · Answer

This can also be done by using partial from the standard library functools  like this   from functools import partial        action with arg   partial action  arg  button   Tk Button master frame  text  press   command action with arg

User · Answer

I have encountered this problem before  too  You can just use lambda   button   Tk Button master frame  text  press  command lambda  action someNumber

[python] How to pass arguments to a Button command in Tkinter?

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