we can add keys and values as followsd['four']= #add an item or update multiple values using the followingd update({'five' 'six' }#add multiple items when we inspect dwe get the followingwe can test for the occurrence of value using the in operatorfor exampleit should be noted that the in operatorwhen applied to dictionariesworks in slightly different way to when it is applied to list when we use the in operator on listthe relationship between the time it takes to find an element and the size of the list is considered linear that isas the size of the list gets biggerthe corresponding time it takes to find an element growsat mostlinearly the relationship between the time an algorithm takes to run compared to the size of its input is often referred to as its time complexity we will talk more about this important topic in the next (and subsequent in contrast to the list objectwhen the in operator is applied to dictionariesit uses hashing algorithm and this has the effect of the increase in time for each lookup almost independent of the size of the dictionary this makes dictionaries extremely useful as way to work with large amounts of indexed data we will talk more about this important topic of rates of growth hashing in lists and pointer structuresand implementationsapplications and tools notice when we print out the key:value pairs of the dictionary it does so in no particular order this is not problem since we use specified keys to look up each dictionary value rather than an ordered sequence of integers as is the case for strings and lists