Iterate over keys of association












3












$begingroup$


How do you iterate over the keys or rules of an association (in any order)? E.g. for 



<|"0"->"a", "1"->"b", "2"->"c"|>


I would like to either iterate over "0", "1", "2" or tuples containing each key and value.



For example, something that performed the equivalent of a python dictionary's items, method would be ideal (which returns a list (or iterator) in the form [(key1, value1), ...], so {{"0", "a"}, {"1", "b"}, {"2", "c"}} here).






associations







share|improve this question











$endgroup$








  • 1




    $begingroup$
    Simply use Map, KeyValueMap or KeyMap?
    $endgroup$
    – Henrik Schumacher
    Dec 5 '18 at 19:20












  • $begingroup$
    Can you tell what exactly do you want to do?
    $endgroup$
    – Kuba♦
    Dec 5 '18 at 21:42










  • $begingroup$
    Woooops! Done! :)
    $endgroup$
    – SLesslyTall
    Dec 6 '18 at 7:40










  • $begingroup$
    @SLesslyTall You see, you want KeyValueMap[List] @ asso but who could've known :)
    $endgroup$
    – Kuba♦
    Dec 6 '18 at 7:53
















3












$begingroup$


How do you iterate over the keys or rules of an association (in any order)? E.g. for 



<|"0"->"a", "1"->"b", "2"->"c"|>


I would like to either iterate over "0", "1", "2" or tuples containing each key and value.



For example, something that performed the equivalent of a python dictionary's items, method would be ideal (which returns a list (or iterator) in the form [(key1, value1), ...], so {{"0", "a"}, {"1", "b"}, {"2", "c"}} here).






associations







share|improve this question











$endgroup$








  • 1




    $begingroup$
    Simply use Map, KeyValueMap or KeyMap?
    $endgroup$
    – Henrik Schumacher
    Dec 5 '18 at 19:20












  • $begingroup$
    Can you tell what exactly do you want to do?
    $endgroup$
    – Kuba♦
    Dec 5 '18 at 21:42










  • $begingroup$
    Woooops! Done! :)
    $endgroup$
    – SLesslyTall
    Dec 6 '18 at 7:40










  • $begingroup$
    @SLesslyTall You see, you want KeyValueMap[List] @ asso but who could've known :)
    $endgroup$
    – Kuba♦
    Dec 6 '18 at 7:53














3












3








3





$begingroup$


How do you iterate over the keys or rules of an association (in any order)? E.g. for 



<|"0"->"a", "1"->"b", "2"->"c"|>


I would like to either iterate over "0", "1", "2" or tuples containing each key and value.



For example, something that performed the equivalent of a python dictionary's items, method would be ideal (which returns a list (or iterator) in the form [(key1, value1), ...], so {{"0", "a"}, {"1", "b"}, {"2", "c"}} here).






associations







share|improve this question











$endgroup$




How do you iterate over the keys or rules of an association (in any order)? E.g. for 



<|"0"->"a", "1"->"b", "2"->"c"|>


I would like to either iterate over "0", "1", "2" or tuples containing each key and value.



For example, something that performed the equivalent of a python dictionary's items, method would be ideal (which returns a list (or iterator) in the form [(key1, value1), ...], so {{"0", "a"}, {"1", "b"}, {"2", "c"}} here).






associations




associations






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Dec 6 '18 at 7:40







SLesslyTall

















asked Dec 5 '18 at 19:15









SLesslyTallSLesslyTall

22317




22317








  • 1




    $begingroup$
    Simply use Map, KeyValueMap or KeyMap?
    $endgroup$
    – Henrik Schumacher
    Dec 5 '18 at 19:20












  • $begingroup$
    Can you tell what exactly do you want to do?
    $endgroup$
    – Kuba♦
    Dec 5 '18 at 21:42










  • $begingroup$
    Woooops! Done! :)
    $endgroup$
    – SLesslyTall
    Dec 6 '18 at 7:40










  • $begingroup$
    @SLesslyTall You see, you want KeyValueMap[List] @ asso but who could've known :)
    $endgroup$
    – Kuba♦
    Dec 6 '18 at 7:53














  • 1




    $begingroup$
    Simply use Map, KeyValueMap or KeyMap?
    $endgroup$
    – Henrik Schumacher
    Dec 5 '18 at 19:20












  • $begingroup$
    Can you tell what exactly do you want to do?
    $endgroup$
    – Kuba♦
    Dec 5 '18 at 21:42










  • $begingroup$
    Woooops! Done! :)
    $endgroup$
    – SLesslyTall
    Dec 6 '18 at 7:40










  • $begingroup$
    @SLesslyTall You see, you want KeyValueMap[List] @ asso but who could've known :)
    $endgroup$
    – Kuba♦
    Dec 6 '18 at 7:53








1




1




$begingroup$
Simply use Map, KeyValueMap or KeyMap?
$endgroup$
– Henrik Schumacher
Dec 5 '18 at 19:20






$begingroup$
Simply use Map, KeyValueMap or KeyMap?
$endgroup$
– Henrik Schumacher
Dec 5 '18 at 19:20














$begingroup$
Can you tell what exactly do you want to do?
$endgroup$
– Kuba♦
Dec 5 '18 at 21:42




$begingroup$
Can you tell what exactly do you want to do?
$endgroup$
– Kuba♦
Dec 5 '18 at 21:42












$begingroup$
Woooops! Done! :)
$endgroup$
– SLesslyTall
Dec 6 '18 at 7:40




$begingroup$
Woooops! Done! :)
$endgroup$
– SLesslyTall
Dec 6 '18 at 7:40












$begingroup$
@SLesslyTall You see, you want KeyValueMap[List] @ asso but who could've known :)
$endgroup$
– Kuba♦
Dec 6 '18 at 7:53




$begingroup$
@SLesslyTall You see, you want KeyValueMap[List] @ asso but who could've known :)
$endgroup$
– Kuba♦
Dec 6 '18 at 7:53










2 Answers
2






active

oldest

votes


















2












$begingroup$

To iterate over the keys of an association, first get the keys in a list using Keys. then use this in your favorite iteration construct (Do, Table, Scan, Map, etc):



In[16]:= assoc = <|"0" -> 0, "1" -> 1, "2" -> 2|>;



In[17]:= Do[Print[x], {x, Keys[assoc]}]



During evaluation of In[17]:= 0



During evaluation of In[17]:= 1



During evaluation of In[17]:= 2





share|improve this answer









$endgroup$





















    6












    $begingroup$

    If you would like to map over the keys to transform them into something else, you can use KeyMap:



    a = <|"0" -> 0, "1" -> 1, "2" -> 2|>;
    
a // KeyMap[("newKey" <> #) &]
    
(* <|"newKey0" -> 0, "newKey1" -> 1, "newKey2" -> 2|> *)


    Otherwise, the good old Map will iterate over the values as if the structure were a list:



    a // Map[("newVal" <> ToString@#) &]
    
(* <|"0" -> "newVal0", "1" -> "newVal1", "2" -> "newVal2"|> *)


    You should also look up KeyValueMap to see if that would make your task easier.



    Edit



    Henrik Schumacher's succinct comment contains everything I have elaborated here. His comment had not been posted when I began writing this answer.






    share|improve this answer









    $endgroup$













      Your Answer





      StackExchange.ifUsing("editor", function () {
      return StackExchange.using("mathjaxEditing", function () {
      StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
      StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
      });
      });
      }, "mathjax-editing");

      StackExchange.ready(function() {
      var channelOptions = {
      tags: "".split(" "),
      id: "387"
      };
      initTagRenderer("".split(" "), "".split(" "), channelOptions);

      StackExchange.using("externalEditor", function() {
      // Have to fire editor after snippets, if snippets enabled
      if (StackExchange.settings.snippets.snippetsEnabled) {
      StackExchange.using("snippets", function() {
      createEditor();
      });
      }
      else {
      createEditor();
      }
      });

      function createEditor() {
      StackExchange.prepareEditor({
      heartbeatType: 'answer',
      autoActivateHeartbeat: false,
      convertImagesToLinks: false,
      noModals: true,
      showLowRepImageUploadWarning: true,
      reputationToPostImages: null,
      bindNavPrevention: true,
      postfix: "",
      imageUploader: {
      brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
      contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
      allowUrls: true
      },
      onDemand: true,
      discardSelector: ".discard-answer"
      ,immediatelyShowMarkdownHelp:true
      });


      }
      });














      draft saved

      draft discarded


















      StackExchange.ready(
      function () {
      StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmathematica.stackexchange.com%2fquestions%2f187393%2fiterate-over-keys-of-association%23new-answer', 'question_page');
      }
      );

      Post as a guest















      Required, but never shown

























      2 Answers
      2






      active

      oldest

      votes








      2 Answers
      2






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes









      2












      $begingroup$

      To iterate over the keys of an association, first get the keys in a list using Keys. then use this in your favorite iteration construct (Do, Table, Scan, Map, etc):



      In[16]:= assoc = <|"0" -> 0, "1" -> 1, "2" -> 2|>;
      

      
In[17]:= Do[Print[x], {x, Keys[assoc]}]
      

      
During evaluation of In[17]:= 0
      

      
During evaluation of In[17]:= 1
      

      
During evaluation of In[17]:= 2





      share|improve this answer









      $endgroup$


















        2












        $begingroup$

        To iterate over the keys of an association, first get the keys in a list using Keys. then use this in your favorite iteration construct (Do, Table, Scan, Map, etc):



        In[16]:= assoc = <|"0" -> 0, "1" -> 1, "2" -> 2|>;
        

        
In[17]:= Do[Print[x], {x, Keys[assoc]}]
        

        
During evaluation of In[17]:= 0
        

        
During evaluation of In[17]:= 1
        

        
During evaluation of In[17]:= 2





        share|improve this answer









        $endgroup$
















          2












          2








          2





          $begingroup$

          To iterate over the keys of an association, first get the keys in a list using Keys. then use this in your favorite iteration construct (Do, Table, Scan, Map, etc):



          In[16]:= assoc = <|"0" -> 0, "1" -> 1, "2" -> 2|>;
          

          
In[17]:= Do[Print[x], {x, Keys[assoc]}]
          

          
During evaluation of In[17]:= 0
          

          
During evaluation of In[17]:= 1
          

          
During evaluation of In[17]:= 2





          share|improve this answer









          $endgroup$



          To iterate over the keys of an association, first get the keys in a list using Keys. then use this in your favorite iteration construct (Do, Table, Scan, Map, etc):



          In[16]:= assoc = <|"0" -> 0, "1" -> 1, "2" -> 2|>;
          

          
In[17]:= Do[Print[x], {x, Keys[assoc]}]
          

          
During evaluation of In[17]:= 0
          

          
During evaluation of In[17]:= 1
          

          
During evaluation of In[17]:= 2






          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Dec 5 '18 at 19:41









          Jason B.Jason B.

          48.1k388189




          48.1k388189























              6












              $begingroup$

              If you would like to map over the keys to transform them into something else, you can use KeyMap:



              a = <|"0" -> 0, "1" -> 1, "2" -> 2|>;
              
a // KeyMap[("newKey" <> #) &]
              
(* <|"newKey0" -> 0, "newKey1" -> 1, "newKey2" -> 2|> *)


              Otherwise, the good old Map will iterate over the values as if the structure were a list:



              a // Map[("newVal" <> ToString@#) &]
              
(* <|"0" -> "newVal0", "1" -> "newVal1", "2" -> "newVal2"|> *)


              You should also look up KeyValueMap to see if that would make your task easier.



              Edit



              Henrik Schumacher's succinct comment contains everything I have elaborated here. His comment had not been posted when I began writing this answer.






              share|improve this answer









              $endgroup$


















                6












                $begingroup$

                If you would like to map over the keys to transform them into something else, you can use KeyMap:



                a = <|"0" -> 0, "1" -> 1, "2" -> 2|>;
                
a // KeyMap[("newKey" <> #) &]
                
(* <|"newKey0" -> 0, "newKey1" -> 1, "newKey2" -> 2|> *)


                Otherwise, the good old Map will iterate over the values as if the structure were a list:



                a // Map[("newVal" <> ToString@#) &]
                
(* <|"0" -> "newVal0", "1" -> "newVal1", "2" -> "newVal2"|> *)


                You should also look up KeyValueMap to see if that would make your task easier.



                Edit



                Henrik Schumacher's succinct comment contains everything I have elaborated here. His comment had not been posted when I began writing this answer.






                share|improve this answer









                $endgroup$
















                  6












                  6








                  6





                  $begingroup$

                  If you would like to map over the keys to transform them into something else, you can use KeyMap:



                  a = <|"0" -> 0, "1" -> 1, "2" -> 2|>;
                  
a // KeyMap[("newKey" <> #) &]
                  
(* <|"newKey0" -> 0, "newKey1" -> 1, "newKey2" -> 2|> *)


                  Otherwise, the good old Map will iterate over the values as if the structure were a list:



                  a // Map[("newVal" <> ToString@#) &]
                  
(* <|"0" -> "newVal0", "1" -> "newVal1", "2" -> "newVal2"|> *)


                  You should also look up KeyValueMap to see if that would make your task easier.



                  Edit



                  Henrik Schumacher's succinct comment contains everything I have elaborated here. His comment had not been posted when I began writing this answer.






                  share|improve this answer









                  $endgroup$



                  If you would like to map over the keys to transform them into something else, you can use KeyMap:



                  a = <|"0" -> 0, "1" -> 1, "2" -> 2|>;
                  
a // KeyMap[("newKey" <> #) &]
                  
(* <|"newKey0" -> 0, "newKey1" -> 1, "newKey2" -> 2|> *)


                  Otherwise, the good old Map will iterate over the values as if the structure were a list:



                  a // Map[("newVal" <> ToString@#) &]
                  
(* <|"0" -> "newVal0", "1" -> "newVal1", "2" -> "newVal2"|> *)


                  You should also look up KeyValueMap to see if that would make your task easier.



                  Edit



                  Henrik Schumacher's succinct comment contains everything I have elaborated here. His comment had not been posted when I began writing this answer.







                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered Dec 5 '18 at 19:25









                  ShredderroyShredderroy

                  1,5201115




                  1,5201115






























                      draft saved

                      draft discarded




















































                      Thanks for contributing an answer to Mathematica Stack Exchange!


                      • Please be sure to answer the question. Provide details and share your research!

                      But avoid …



                      • Asking for help, clarification, or responding to other answers.

                      • Making statements based on opinion; back them up with references or personal experience.


                      Use MathJax to format equations. MathJax reference.


                      To learn more, see our tips on writing great answers.




                      draft saved


                      draft discarded














                      StackExchange.ready(
                      function () {
                      StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmathematica.stackexchange.com%2fquestions%2f187393%2fiterate-over-keys-of-association%23new-answer', 'question_page');
                      }
                      );

                      Post as a guest















                      Required, but never shown





















































                      Required, but never shown














                      Required, but never shown












                      Required, but never shown







                      Required, but never shown

































                      Required, but never shown














                      Required, but never shown












                      Required, but never shown







                      Required, but never shown







                      -

                      Popular posts from this blog

                      Probability when a professor distributes a quiz and homework assignment to a class of n students.

                      Image
                      0 0 $begingroup$ Need help with this problem. Suppose our lazy professor collects a quiz and a homework assignment from a class of n students one day, then distributes both the quizzes and the homework assignments back to the class in a random fashion for grading. Each student receives one quiz and one homework assignment to grade. (a) What is the probability that every student receives someone else's quiz to grade, and someone else's homework to grade? (b) What is the probability that no student receives both their own quiz and their own homework assignment to grade? In this case, some students may receive their own quiz, and others may receive their own homework assignment. (c) Compute the limiting probability as n approaches infinity in each case. ...
                      Read more

                      Aardman Animations

                      Image
                      Aardman Animations, Ltd. Aardman Animations Tipo privada Atividade Animação em stop-motion , Animação em CGI Fundação 1972 Fundador(es) Peter Lord David Sproxton Sede Bristol, Inglaterra  Reino Unido Proprietário(s) Dreamworks Pessoas-chave Peter Lord David Sproxton Nick Park Divisões Aardman Features Aardman Digital Aardman Commercials Aardman Broadcast Aardman International Aardman Rights Aardman Effects Aardman 3-D Systems Aardman Nathan Love AardBoiled Website oficial aardman.com ...
                      Read more

                      Are they similar matrix

                      Image
                      0 $begingroup$ Do $begin{bmatrix} 0&i&0\0&0&1\0&0&0 end{bmatrix} $ and $begin{bmatrix} 0&0&0\-i&0&0\0&1&0 end{bmatrix} $ are similar.Is this True/false Clearly both are nilpotent and one is conjucate transpose of other but how to know if they are similar.i'm stuck. Please help me linear-algebra vector-spaces eigenvalues-eigenvectors generalizedeigenvector share | cite | improve this question edited Dec 10 '18 at 6:38 Vasanth Kris asked Dec 10 '18 at 6:19 ...
                      Read more