Data Structures 810:052 More with Python collections

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Data Structures810052More with Python
collections
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A String is a sequence/collection of data
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Strings are immutable

• gtgtgt rhyme 1,2,"buckle","my","shoe"
• gtgtgt rhyme4"flu
• gtgtgt rhyme
• 1, 2, 'buckle', 'my', 'flu'
• gtgtgt lastname Schafer
• gtgtgt lastname3o
• Traceback (most recent call last)
• File "ltpyshell21gt", line 1, in ltmodulegt
• lastname3o
• TypeError 'str' object does not support item
  assignment

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But Strings respond to additional methods
(The string module can be imported to provide
more string operations.)
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Tuples

• A tuple is an immutable sequence of data defined
  by a sequence of comma-separated items enclosed
  in parentheses
• student1 (Bob, 123456, Jr, 3.12)
• student2 (Sally, 654321, Fr, 0.0)
• Fields of a tuple can be unpacked to its
  components using a single assignment statement
  as
• name, idnum, rank, gpa student1

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Dictionary

• A dictionary is an unordered set of key-value
  pairs (written as keyvalue).
• Keys must be unique and immutable (e.g.,
  numerics, strings, tuples of immutable objects).
  
• Dictionaries are typically used to lookup the
  value corresponding to a specified key.

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Dictionary

• Dictionaries can be written as comma-separated
  keyvalue pairs enclosed in curly braces. For
  example
• phoneNumbers fienup35918,
• gray35917,
• east32939,
• drake35811,
• schafer32187

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Dictionary

• Access to individual keyvalue pairs looks
  syntactically like a sequence lookup using a key
  instead of an index.
• For example
• gtgtgt phoneNumberseast
• 32939
• gtgtgt phoneNumberswallingford35919

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Dictionary Methods
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Defining your own classesChapter 8Intro to
Lab02
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Data types so far

• Numbers
• Contain no methods and one value
• Tuples
• Contain no methods and several values
• Strings
• Contain methods and one value
• Lists and Dictionaries
• Contain methods and several values

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These are examples of Objects

• Objects normally consist of
• Values (data) often referred to as State
• Methods often referred to as Behavior

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So what do you do if you want to create a new
type of Object

• Earlier I made reference to data about a student
• First Name string
• Middle Initial character
• Last Name - string
• Age - integer
• GPA floating point number
• Hometown - string
• Do they have an advisor hold boolean

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How could I store data about a Student as a
single object?

• Could use Tuples
• student1 (James , B , Jones , 19 , 3.24 ,
  Ames , True)
• What are some of the problems with this?

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Instead we might decide to make our own Student
class

• !/usr/local/bin/python
• class Student
• def __init__(self,first,middle,last,age,gpa,ho
  metown,hold)
• self.firstfirst
• self.middlemiddle
• self.lastlast
• self.ageage
• self.gpagpa
• self.hometownhometown
• self.holdhold

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Instead we might decide to make our own Student
class

• class Student
• def getName(self)
• return self.first" "self.middle"
  "self.last
• def getAge(self)
• return self.age
• def getGPA(self)
• return self.gpa
• def modifyGPA(self,newGPA)
• self.gpanewGPA
• def hasHold(self)
• return self.hold

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Demoing some features

• def studentDemo()
• student1Student("John","A","Doe",23,4.0,"Ames
  ",True)
• print student1.getName()
• print student1.getGPA()
• student1.modifyGPA(3.66)
• print student1.getGPA()
• print student1.hasHold()