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Python Data Structures

Python Data Structures. CS 265 Seth Simpson. Lists. Creating Lists exampleList = [1,3,5,7,9] List methods Append( element) – appends element to end Extend( list ) – extends the list with another list Insert( position, element) – insert element at the given position

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Python Data Structures

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  1. Python Data Structures CS 265 Seth Simpson

  2. Lists • Creating Lists • exampleList = [1,3,5,7,9] • List methods • Append(element) – appends element to end • Extend(list) – extends the list with another list • Insert(position, element) – insert element at the given position • Remove(element) – removes the first occurrence of the element

  3. Lists (Cont) • More List methods • Pop(index) – Remove and return the element at index (last element by default) • Index(element) – returns index of the first occurrence of element • Count(element) – returns the number of times element appears in the list • Sort() – sorts the list • Reverse() – reverses the list

  4. Example of List Methods

  5. Lists as Stacks • Last in – First out • List pop function enables us to treat lists as stacks.

  6. Lists as Queues • First in – first out • Popping end elements of a list is fast because the elements don’t need to be rearranged • Popping from the front of a list is slow because the list needs to be rearranged

  7. List Filtering • Filter(function name, list) • Returns a sequence of items for which function(item) is true. • Example:

  8. List Mapping • Map(function name, list) • Calls the function for each value in the list and outputs the results as list • Example:

  9. List Reducing • Reduce(function name, list) • Returns a single value by computing the function value on the first two elements, then the result of that with the next element and so on.

  10. Sets • Unordered collection with no duplicates

  11. Sets (Cont)

  12. Dictionaries • Unsorted set of Key : Value pairs

  13. Dictionaries (Cont) • Can also call the dict() constructor to create a dictionary. • Printing out Dictionaries

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