Create Frequency Dictionary from List

PythonPythonBeginner
Practice Now

This tutorial is from open-source community. Access the source code

Introduction

In this challenge, you will create a Python function that takes a list as an argument and returns a dictionary with the unique values of the list as keys and their frequencies as the values. This is a common task in data analysis and can be useful in many different applications.


Skills Graph

%%%%{init: {'theme':'neutral'}}%%%% flowchart RL python(("`Python`")) -.-> python/BasicConceptsGroup(["`Basic Concepts`"]) python(("`Python`")) -.-> python/ControlFlowGroup(["`Control Flow`"]) python(("`Python`")) -.-> python/DataStructuresGroup(["`Data Structures`"]) python(("`Python`")) -.-> python/FunctionsGroup(["`Functions`"]) python(("`Python`")) -.-> python/ModulesandPackagesGroup(["`Modules and Packages`"]) python(("`Python`")) -.-> python/PythonStandardLibraryGroup(["`Python Standard Library`"]) python/BasicConceptsGroup -.-> python/comments("`Comments`") python/BasicConceptsGroup -.-> python/variables_data_types("`Variables and Data Types`") python/BasicConceptsGroup -.-> python/numeric_types("`Numeric Types`") python/ControlFlowGroup -.-> python/for_loops("`For Loops`") python/DataStructuresGroup -.-> python/lists("`Lists`") python/DataStructuresGroup -.-> python/tuples("`Tuples`") python/DataStructuresGroup -.-> python/dictionaries("`Dictionaries`") python/FunctionsGroup -.-> python/function_definition("`Function Definition`") python/ModulesandPackagesGroup -.-> python/importing_modules("`Importing Modules`") python/ModulesandPackagesGroup -.-> python/using_packages("`Using Packages`") python/ModulesandPackagesGroup -.-> python/standard_libraries("`Common Standard Libraries`") python/PythonStandardLibraryGroup -.-> python/data_collections("`Data Collections`") python/FunctionsGroup -.-> python/build_in_functions("`Build-in Functions`") subgraph Lab Skills python/comments -.-> lab-13112{{"`Create Frequency Dictionary from List`"}} python/variables_data_types -.-> lab-13112{{"`Create Frequency Dictionary from List`"}} python/numeric_types -.-> lab-13112{{"`Create Frequency Dictionary from List`"}} python/for_loops -.-> lab-13112{{"`Create Frequency Dictionary from List`"}} python/lists -.-> lab-13112{{"`Create Frequency Dictionary from List`"}} python/tuples -.-> lab-13112{{"`Create Frequency Dictionary from List`"}} python/dictionaries -.-> lab-13112{{"`Create Frequency Dictionary from List`"}} python/function_definition -.-> lab-13112{{"`Create Frequency Dictionary from List`"}} python/importing_modules -.-> lab-13112{{"`Create Frequency Dictionary from List`"}} python/using_packages -.-> lab-13112{{"`Create Frequency Dictionary from List`"}} python/standard_libraries -.-> lab-13112{{"`Create Frequency Dictionary from List`"}} python/data_collections -.-> lab-13112{{"`Create Frequency Dictionary from List`"}} python/build_in_functions -.-> lab-13112{{"`Create Frequency Dictionary from List`"}} end

Value Frequencies

Problem

Write a Python function called value_frequencies(lst) that takes a list as an argument and returns a dictionary with the unique values of the list as keys and their frequencies as the values.

To solve this problem, you can follow these steps:

  1. Create an empty dictionary to store the frequencies of each unique element.
  2. Loop through the list and use collections.defaultdict to store the frequencies of each unique element.
  3. Use dict() to return a dictionary with the unique elements of the list as keys and their frequencies as the values.

Your function should return the dictionary with the unique values and their frequencies.

Example

value_frequencies(['a', 'b', 'a', 'c', 'a', 'a', 'b']) ## { 'a': 4, 'b': 2, 'c': 1 }

Summary

In this challenge, you learned how to create a Python function that takes a list as an argument and returns a dictionary with the unique values of the list as keys and their frequencies as the values. This is a useful technique in data analysis and can be used in many different applications.

Other Python Tutorials you may like