Lecture 14: Nested Lists, Tuples, and Dictionaries
[Pages:25]
Lecture 14: Nested Lists, Tuples, and Dictionaries
(Sections 11.1-11.5, 12.1-12)
CS 1110 Introduction to Computing Using Python
[E. Andersen, A. Bracy, D. Gries, L. Lee, S. Marschner, C. Van Loan, W. White]
Announcements
? A3 Tentative release date: Mon Mar 19-Thu Mar 22; tentative time for completion: somewhere between 1 and 2 weeks. Similar to A3 from Spring 2017.
? Prelim 1 Grading this weekend. Grades will come out before the drop deadline.
2
Next week: Recursion
? Tuesday and Thursday: Recursion. ? Reading: 5.8-5.10
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Nested Lists
? Lists can hold any objects ? Lists are objects ? Therefore lists can hold other lists!
b = [3, 1] c = [1, 4, b] a = [2, 1] x = [1, a, c, 5]
x[1]
x[2]
x[2][2]
x = [1, [2, 1], [1, 4, [3, 1]], 5]
x[0] x[1][1] x[2][0] x[2][2][0]
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Two Dimensional Lists
Table of Data
0 1 2 3 0 5473 1 4897 2 5123 3 4129 4 6780
Each row, col has a value
Images
0 1 2 3 4 5 6 7 8 9 10 1112
0
1
2
3 4
Each row, col has
5
an RGB value
6
7
8
9
10
11
12
Store them as lists of lists (row-major order) d = [[5,4,7,3],[4,8,9,7],[5,1,2,3],[4,1,2,9],[6,7,8,0]]
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Overview of Two-Dimensional Lists
? Access value at row 3, col 2: d[3][2]
? Assign value at row 3, col 2: d[3][2] = 8
? Number of rows of d:
? len(d)
? Number of cols in row r of d:
? len(d[r])
0 1 2 3 d 0 5473
1 4897 2 5123 3 4129 4 6780
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How Multidimensional Lists are Stored
? b = [[9, 6, 4], [5, 7, 7]]
9 6 4 5 7 7
b id1
id1
0 id2 1 id3
id2
09 16 24
id3
05 17 27
? b holds id of a one-dimensional list
? Has len(b) elements
? b[i] holds id of a one-dimensional list
? Has len(b[i]) elements
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Ragged Lists: Rows w/ Different Length
? b = [[17,13,19],[28,95]]
b id1
id1
0 id2 1 id3
id2
0 17 1 13 2 19
id3
0 28 1 95
8
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