Data Structures 810:052 More with Python collections

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Data Structures810052More with Python
collections
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Review - Lists

• A Python list is an ordered, mutable, collection
  of comma-separated values of any data type
  enclosed in square brackets
• faculty Schafer , Fienup, East ,
  Drake
• rhyme 1, 2, buckle, your , shoe
• empty this is an empty list

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Your turn

• Complete the Working with Lists as Collections
  and Lists are Mutable pt. 1 sections of your
  handout

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Additional methods just for lists
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Your Turn

• Complete the Lists are mutable pt. 2 activity
  on your handout

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The range function

• As you get started, one of the most commonly used
  lists is created by the range function.
• The range() function is used to generate a list
  of equally spaced integers
• range(start, stop ,step)

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The range function

• gtgtgt range(10)
• 0,1,2,3,4,5,6,7,8,9
• gtgtgt range(2,10)
• 2,3,4,5,6,7,8,9
• gtgtgt range(2,10,2)
• 2,4,6,8

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Your turn

• Complete the Range activity on your handout

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One place we use lists

• Iteration Python provides two forms of
  iteration
• for
• while

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The for statement

• The for statement is designed to iterate over a
  list or other sequence of data.
• Its syntax is
• for variable reference_name in list_name
• block
• of
• code

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The for statement

• gtgtgt wordlist linux, windows, mac
• gtgtgt for word in wordlist
• print word str(len(word))
• linux 5
• windows 7
• mac 3

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The for statement

• gtgtgt for num in range(1,11)
• print str(num)
• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10

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The while statement

• The while statement is designed to continue to
  loop as long as ome condition is true
• Its syntax is
• while boolean_condition
• block
• of
• code

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The while statement

• gtgtgt number 1
• gtgtgt while numberlt10
• print str(number)
• number number 1
• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9

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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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Your Turn

• Complete the section named Working with Strings
  on your handout

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Tuples

• A tuple is an immutable sequence of data defined
  by a sequence of commea-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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Your Turn

• Complete the Tuples section on your handout

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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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Your Turn

• Complete the Dictionary section of your handout