5c-dictionaries.md

Python Data Structures - Dictionaries

Index/ Python

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Objective

Learn the dictionary data structures in python

Reference

Essentials

• From Byte of Python read the following chapters
  • Data structures read dictionary section
• From Dive into Python3, read the following chapters
  • Native data types - read dictionary section

Checklist

After completing the exercises below, you should be comfortable with

• Using dictionaries

Exercises

Difficulty Level

★☆☆ - Easy
★★☆ - Medium
★★★ - Challenging
★★★★ - Bonus

A - Dictionary Basics

A1 - Create a dictionary with following contents (★☆☆)

    a -> 2,
    c -> 5,
    b -> 1,
    d -> 3

A2 - given a key, get a value (★☆☆)

what is the value for key 'a'?
what is the value for key 'x' ?

A3 - add a Key-value to map (★☆☆)

Add e -> 4 to the above map

A4 - Check if given key is in a map? (★☆☆)

key : 'a'
key : 'x'

A5 - Loop through a map and print all key value pairs (★☆☆)

A6 - create a dict that returns a default value for non existing keys (★☆☆)

For example the dict has following KV

    a -> 2,
    c -> 5,
    b -> 1,
    d -> 3

existing key : d['a'] --> 2
non existing key returns zero : d['x'] --> 0

B - Medium

B1 - de-dupe (★★☆)

• Create a list of 50 random numbers between 1 and 100 (including).
• print only unique numbers from the list, eliminating duplicates

B2 : Get the frequency of the elements in a list (★★☆)

For example if the list is
['a', 'b', 'a', 'c', 'b', 'a'] Expected output is :

  'a' -> 3,
  'b' -> 2,
  'c' -> 1

B3 : Sort dictionary by values (★★☆)

For example, if the dictionary is

  a -> 4
  b -> 5
  c -> 2

The expected output is :

  c -> 2 
  a -> 4
  b -> 5

More Exercises

• https://www.w3resource.com/python-exercises/dictionary/