list, tuple, string, linked listcontents.kocw.net/kocw/document/2014/handong/kimyoungsup/9.pdf2....

ITP 20005 Programming LanguagesChapter 2 Building Abstractions with Data

2.1 Introduction2.2 Data Abstraction2.3 Sequences

List, Tuple, String, Linked List

Major references: 1. Structure and Interpretation of Computer Programs(SICP) by Abelson and Sussman, MIT

Composing Programs by John DeNero, Google2. MITx OPENCOURSEWARE(OCW) 6.00 SC Lecture 3. UC Berkley CS61A Lecture 4. Python, Wikipedia and many on-line resources.Prof. Youngsup Kim, idebtor@handong.edu, 2014 Programming Languages, CSEE Dept., Handong Global University

ITP 20005 Programming LanguagesChapter 2 Building Abstractions with Data

2.1 Introduction2.2 Data Abstraction2.3 Sequences

List, Tuple, String, Linked List

Major references: 1. Structure and Interpretation of Computer Programs(SICP) by Abelson and Sussman, MIT

Composing Programs by John DeNero, Google2. MITx OPENCOURSEWARE(OCW) 6.00 SC Lecture 3. UC Berkley CS61A Lecture 4. Python, Wikipedia and many on-line resources.Prof. Youngsup Kim, idebtor@handong.edu, 2014 Programming Languages, CSEE Dept., Handong Global University

Python List built-in methods, accessing elements, selection, slicing, recursive functions,list comprehension

3

2.3 The Sequence Abstraction

Christ

4

2.3 The Sequence Abstraction

Christ

in whom are hidden all the treasures of wisdom and knowledge

Col2:3

5

2.3 The Sequence Abstraction

Christ

in whom are hidden all the treasures of wisdom and knowledge

Col2:3

Taste and see that the LORD is good;Ps34:8

6

2.3 The Sequence Abstraction

Christ

in whom are hidden all the treasures of wisdom and knowledge

Col2:3

Taste and see that the LORD is good;Ps34:8

The fear of the LORD is the beginning of knowledge,

but fools despise wisdom and discipline.

Pro1:7

7

2.3 The Sequence Abstraction

red, orange, yellow, green, blue, indigo, violet.

8

2.3 The Sequence Abstraction

red, orange, yellow, green, blue, indigo, violet.

There isn't just one sequence type (in Python or in general)

9

2.3 The Sequence Abstraction

red, orange, yellow, green, blue, indigo, violet.

There isn't just one sequence type (in Python or in general)

This abstraction is a collection of behaviors:

10

2.3 The Sequence Abstraction

red, orange, yellow, green, blue, indigo, violet.

There isn't just one sequence type (in Python or in general)

This abstraction is a collection of behaviors:

Length. A sequence has a finite length.

Element selection. A sequence has an element corresponding to any non‐negative integer index less than its length, starting at 0 for the first element.

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2.3 The Sequence Abstraction

red, orange, yellow, green, blue, indigo, violet.

There isn't just one sequence type (in Python or in general)

This abstraction is a collection of behaviors:

0 , 1 , 2 , 3 , 4 , 5 , 6 .

Length. A sequence has a finite length.

Element selection. A sequence has an element corresponding to any non‐negative integer index less than its length, starting at 0 for the first element.

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2.3 The Sequence Abstraction

red, orange, yellow, green, blue, indigo, violet.

There isn't just one sequence type (in Python or in general)

This abstraction is a collection of behaviors:

Length. A sequence has a finite length.

Element selection. A sequence has an element corresponding to any non‐negative integer index less than its length, starting at 0 for the first element.

0 , 1 , 2 , 3 , 4 , 5 , 6 .

The sequence abstraction is shared among several types,including tuples.

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2.3 Python Sequence Abstraction

Built-in sequence types provide the following behavior.

>>> a = (1, 2, 3)>>> b = tuple([4, 5, 6, 7])

Type‐specificconstructor

>>> len(a), len(b)(3, 4)

length

Elementselection

>>> a[1], b[‐1](2, 7)

Slicing>>> a[1:3], b[1:1], a[:2], b[1:]((2, 3), (), (1, 2), (5, 6, 7))

Membership>>> 2 in a, 4 in a, 4 not in b(True, False, False)

tuple

list : variable length,mutable objectstay tuned for more

tuple

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2.3 Python Sequence Abstraction

Built-in sequence types provide the following behavior.

>>> a = (1, 2, 3)>>> b = tuple([4, 5, 6, 7])

Type‐specificconstructor

>>> len(a), len(b)(3, 4)

length

Elementselection

>>> a[1], b[‐1](2, 7)

Slicing>>> a[1:3], b[1:1], a[:2], b[1:]((2, 3), (), (1, 2), (5, 6, 7))

Membership>>> 2 in a, 4 in a, 4 not in b(True, False, False)

tuple

list : variable length,mutable objectstay tuned for more

tuple

Counting from the end; -1 is the last element

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2.3 List as a Type in Python

Tuple: fixed-length, immutable sequence of Python objects

List: variable-length, and mutable

>>> a = [3, 1, 2]>>> a[3, 1, 2]>>> len(a)3>>> a[1]1>>> c, d = a, a[:]>>> a, c, d([3, 1, 2], [3, 1, 2], [3, 1, 2])>>> c[0] = 4>>> a, c, d([4, 1, 2], [4, 1, 2], [3, 1, 2])>>> d[0] = 5>>> a, c, d([4, 1, 2], [4, 1, 2], [5, 1, 2])>>> a[1:2] = [7, 8, 9]>>> a, c, d([4, 7, 8, 9, 2], [4, 7, 8, 9, 2], [5, 1, 2])

Create a list using square brackets:

Lists are sequences.

Bind another name to a list or a slice of a list.

Modify contents of a list.

wut()?

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2.3 Python Sequence Iteration

Python has a special statement for iterating over the elements in a sequence

def count(s, value):

total = 0

for elem in s:

if elem == value:

total += 1

return total

Name ‘elem’ bound in the first frame of the current environment

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2.3 Python Sequence Iteration

For Statement Execution Procedure

for <name> in <expression>:

<suite>

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2.3 Python Sequence Iteration

For Statement Execution Procedure

for <name> in <expression>:

<suite>

1. Evaluate the header <expression>, which must yield an iterable value.

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2.3 Python Sequence Iteration

For Statement Execution Procedure:

for <name> in <expression>:

<suite>

1. Evaluate the header <expression>, which must yield an iterable value.

2. For each element in that sequence, in order:• Bind <name> to that element in the first frame of the current

environment.• Execute the <suite>.

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2.3 List Comprehensions see 2.3.3

One large expression that combines mapping and filtering to produce an iterable.

• Evaluates to an iterable.• <iter exp> is evaluated when the generator expression is evaluated.• Remaining expressions are evaluated when elements are accessed.

No‐filter version: [ <map exp> for <name> in <iter exp> ]

Stay tuned: Precise evaluation rule introduced in Chapter 4.

[<map exp> for <name> in <iter exp> if <filter exp>]

[Demo]