Bound method error

Question

I am creating a word parsing class and keep getting a   bound method Word Parser sort word list of  lt main Word Parser instance at 0x1037dd3b0   error when I run this   class Word Parser         docstring for Word Parser        def   init   self  sentences           self sentences   sentences      def parser self           self word list   self sentences split        def sort word list self           self sorted word list   self word list sort        def num words self           self num words   len self word list   test   Word Parser  mary had a little lamb   test parser   test sort word list   test num words   print test word list print test sort word list print test num words

User · Answer

The syntax problem is shadowing method and variable names. In the current version sort_word_list() is a method, and sorted_word_list is a variable, whereas num_words is both. Also, list.sort() modifies the list and replaces it with a sorted version; the sorted(list) function actually returns a new list.

But I suspect this indicates a design problem. What's the point of calls like

test.parser()
test.sort_word_list()
test.num_words()

which don't do anything? You should probably just have the methods figure out whether the appropriate counting and/or sorting has been done, and, if appropriate, do the count or sort and otherwise just return something.

E.G.,

def sort_word_list(self):
   if self.sorted_word_list is not None:
      self.sorted_word_list = sorted(self.word_list)
   return self.sorted_word_list

(Alternately, you could use properties.)

User · Answer

Your helpful comments led me to the following solution   class Word Parser         docstring for Word Parser        def   init   self  sentences           self sentences   sentences      def parser self           self word list   self sentences split           word list              word list   self word list         return word list      def sort word list self           self sorted word list   sorted self sentences split            sorted word list   self sorted word list         return sorted word list      def get num words self           self num words   len self word list          num words   self num words         return num words  test   Word Parser  mary had a little lamb   test parser   test sort word list   test get num words   print test word list print test sorted word list print test num words   and returns    mary    had    a    little    lamb     a    had    lamb    little    mary   5  Thank you all

User · Answer

For this thing you can use  property as an decorator  so you could use instance methods as attributes  For example  class Word Parser      def   init   self  sentences           self sentences   sentences       property     def parser self           self word list   self sentences split         property     def sort word list self           self sorted word list   self word list sort         property     def num words self           self num words   len self word list   test   Word Parser  quot mary had a little lamb quot   test parser   test sort word list   test num words   print test word list print test sort word list print test num words  so you can use access the attributes without calling  i e   without the

User · Answer

You have an instance method called num words  but you also have a variable called num words  They have the same name  When you run num words    the function replaces itself with its own output  which probably isn t what you want to do  Consider returning your values   To fix your problem  change def num words to something like def get num words and your code should work fine  Also  change print test sort word list to print test sorted word list

User · Answer

There s no error here  You re printing a function  and that s what functions look like   To actually call the function  you have to put parens after that  You re already doing that above  If you want to print the result of calling the function  just have the function return the value  and put the print there  For example   print test sort word list     On the other hand  if you want the function to mutate the object s state  and then print the state some other way  that s fine too   Now  your code seems to work in some places  but not others  let s look at why    parser sets a variable called word list  and you later print test word list  so that works  sort word list sets a variable called sorted word list  and you later print test sort word list   that is  the function  not the variable  So  you see the bound method   Also  as Jon Clements points out  even if you fix this  you re going to print None  because that s what sort returns   num words sets a variable called num words  and you again print the function   but in this case  the variable has the same name as the function  meaning that you re actually replacing the function with its output  so it works  This is probably not what you want to do  however     There are cases where  at first glance  that seems like it might be a good idea   you only want to compute something once  and then access it over and over again without constantly recomputing that  But this isn t the way to do it  Either use a  property  or use a memoization decorator

User · Answer

This problem happens as a result of calling a method without brackets  Take a look at the example below   class SomeClass object       def   init   self           print  I am starting       def some meth self           print  I am a method     x   SomeClass       Not adding the bracket after the method call would result in method bound error     print x some meth     However this is how it should be called and it does solve it     x some meth

User · Answer

I think you meant print test sorted word list instead of print test sort word list   In addition list sort   sorts a list in place and returns None  so you probably want to change sort word list   to do the following   self sorted word list   sorted self word list    You should also consider either renaming your num words   function  or changing the attribute that the function assigns to  because currently you overwrite the function with an integer on the first call

[python] Bound method error

Examples related to python

Examples related to class