Understanding lambda in python and using it to pass multiple arguments

Question

After reading everything I can find  on lambda  I still don t understand how to make it do what I want   Everyone uses the example   lambda x  y   x   y   Why do you need to state both x and y before the    Also how do you make it return multiple arguments   for example   self buttonAdd 1   Button self  text      command lambda   self calculate self buttonOut 1 grid info    1     This works just fine  But the following code does not   self entry 1 bind   lt Return gt    lambda   self calculate self buttonOut 1 grid info    1     It yields the error      TypeError     takes no arguments  1 given

User · Answer

Why do you need to state both x and y before the      Because it s a function definition and it needs to know what parameters the function accepts  and in what order  It can t just look at the expression and use the variables names in that  because some of those names you might want to use existing local or global variable values for  and even if it did that  it wouldn t know what order it should expect to get them   Your error message means that Tk is calling your lambda with one argument  while your lambda is written to accept no arguments  If you don t need the argument  just accept one and don t use it   Demosthenex has the code  I would have posted it but was beaten to it

User · Answer

Why do you need to state both  x  and  y  before the        Because a lambda is  conceptually  the same as a function  just written inline  Your example is equivalent to   def f x  y    return x   y   just without binding it to a name like f      Also how do you make it return multiple arguments    The same way like with a function  Preferably  you return a tuple   lambda x  y   x y  x-y    Or a list  or a class  or whatever   The thing with self entry 1 bind should be answered by Demosthenex

User · Answer

Why do you need to state both  x  and  y  before the        You could actually in some situations when you have only one argument  do not put the x and y before        gt  gt  gt  flist       gt  gt  gt  for i in range 3           flist append lambda   i    but the i in the lambda will be bound by name  so    gt  gt  gt  flist 0    2  gt  gt  gt  flist 2    2  gt  gt  gt    different from what you may want

User · Answer

I believe bind always tries to send an event parameter  Try   self entry 1 bind   lt Return gt    lambda event  self calculate self buttonOut 1 grid info    1     You accept the parameter and never use it

[python] Understanding lambda in python and using it to pass multiple arguments

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