Passing functions with arguments to another function in Python

Question

Is it possible to pass functions with arguments to another function in Python   Say for something like   def perform function       return function     But the functions to be passed will have arguments like   action1   action2 p  action3 p r

User · Answer

Here is a way to do it with a closure       def generate add mult func func           def function generator x               return reduce func range 1 x           return function generator      def add x y           return x y      def mult x y           return x y      adding generate add mult func add      multiplying generate add mult func mult       print adding 10      print multiplying 10

User · Answer

You can use the partial function from functools like so   from functools import partial  def perform f       f    perform Action1  perform partial Action2  p   perform partial Action3  p  r     Also works with keywords  perform partial Action4  param1 p

User · Answer

Use functools partial  not lambdas  And ofc Perform is a useless function  you can pass around functions directly   for func in  Action1  partial Action2  p   partial Action3  p  r      func

User · Answer

This is what lambda is for  def perform f       f    perform lambda  action1    perform lambda  action2 p   perform lambda  action3 p  r

User · Answer

This is called partial functions and there are at least 3 ways to do this  My favorite way is using lambda because it avoids dependency on extra package and is the least verbose  Assume you have a function add x  y  and you want to pass add 3  y  to some other function as parameter such that the other function decides the value for y   Use lambda    generic function takes op and its argument def runOp op  val       return op val     declare full function def add x  y       return x y    run example def main        f   lambda y  add 3  y      result   runOp f  1    is 4   Create Your Own Wrapper  Here you need to create a function that returns the partial function  This is obviously lot more verbose     generic function takes op and its argument def runOp op  val       return op val     declare full function def add x  y       return x y    declare partial function def addPartial x       def  wrapper y           return add x  y      return  wrapper    run example def main        f   addPartial 3      result   runOp f  1    is 4   Use partial from functools  This is almost identical to lambda shown above  Then why do we need this  There are few reasons  In short  partial might be bit faster in some cases  see its implementation  and that you can use it for early binding vs lambda s late binding   from functools import partial    generic function takes op and its argument def runOp op  val       return op val     declare full function def add x  y       return x y    run example def main        f   partial add  3      result   runOp f  1    is 4

User · Answer

months later  a tiny real example where lambda is useful  partial not  say you want various 1-dimensional cross-sections through a 2-dimensional function  like slices through a row of hills  quadf  x  f   takes a 1-d f and calls it for various x  To call it for vertical cuts at y   -1 0 1 and horizontal cuts at x   -1 0 1   fx1   quadf  x  lambda x  f  x  1    fx0   quadf  x  lambda x  f  x  0    fx 1   quadf  x  lambda x  f  x  -1    fxy   parabola  y  fx 1  fx0  fx1    f 1y   quadf  y  lambda y  f  -1  y    f0y   quadf  y  lambda y  f  0  y    f1y   quadf  y  lambda y  f  1  y    fyx   parabola  x  f 1y  f0y  f1y     As far as I know  partial can t do this --  quadf  y  partial  f  x 1    TypeError  f   got multiple values for keyword argument  x     How to add tags numpy  partial  lambda to this

User · Answer

Do you mean this  def perform fun   args       fun  args   def action1 args         something  def action2 args         something  perform action1  perform action2  p  perform action3  p  r

[python] Passing functions with arguments to another function in Python?

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