Description

More programming with lists

Starting Lab 7
• Open a browser and log into Brightspace
• On the left hand side under Labs tab, find lab6 material
contained in lab7-students.pdf file
• Download that file to the Desktop.
2
Before starting, always make sure you
are running Python 3
This slide is applicable to all labs, exercises, assignments … etc
ALWAYS MAKE SURE FIRST that you are running Python 3
That is, when you click on IDLE (or start python any other way)
look at the first line that the Python shell displays. It should say
Python 3 (and then some extra digits)
If you do not know how to do this, read the material provided
with Lab 1. It explains it step by step
3
Task (to be completed at home)
I strongly encourage you to complete these two quizes at home. Leave
the time in the lab for questions to TAs about quiz problems whose
solution you do not understand.
Go to coursera webpage and log in.
1.Go to the following link to and complete the Quiz of Week 4. You will
find the quiz at the bottom of the page
https://www.coursera.org/learn/learn-to-program/home/week/4
2.Go to the following link to and complete the Quiz of Week 5. You will
find the quiz at the bottom of the page
https://www.coursera.org/learn/learn-to-program/home/week/5
• You can do each quiz more than once.
4
Programming Exercises (the most important lab)
The following exercises are easily the most important exercises in this
whole semester. Solving these problems (by yourself preferably) should
greatly increase your understanding of computational problem solving
and programming.
Do as many as possible (preferably all) of the following 13 programming
exercises from your textbook by Perkovic. 11 out of 13 are mandatory
for this lab (your choice which 11) — see the slides to come.
Introduction to Computing Using Python: An Application Development
Focus, 2nd Edition, Ljubomir Perkovic
Sometimes the author uses a word “outputs”. By that he means “prints”
First recall from the next 4 slides, list (and few string) functions and
methods that you will need.
Introduction to Computing Using Python by Lj. Perkovic
List operators and functions
Like strings, lists can be manipulated with
operators and functions
>>> lst = [1, 2, 3]
>>> lstB = [0, 4]
>>> 4 in lst
False
>>> 4 not in lst
True
>>> lst + lstB
[1, 2, 3, 0, 4]
>>> 2*lst
[1, 2, 3, 1, 2, 3]
>>> lst[0]
1
>>> lst[1]
2
>>> lst[-1]
3
>>> len(lst)
3
>>> min(lst)
1
>>> max(lst)
3
>>> sum(lst)
6
>>> help(list
…
Usage Explanation
x in lst x is an item of lst
x not in lst x is not an item of lst
lst + lstB Concatenation of lst and lstB
lst*n, n*lst Concatenation of n copies of lst
lst[i] Item at index i of lst
len(lst) Number of items in lst
min(lst) Minimum item in lst
max(lst) Maximum item in lst
sum(lst) Sum of items in lst
Introduction to Computing Using Python by Lj. Perkovic
Lists methods
>>> lst = [1, 2, 3]
>>> lst.append(7)
>>> lst.append(3)
>>> lst
[1, 2, 3, 7, 3]
>>> lst.count(3)
2
>>> lst.remove(2)
>>> lst
[1, 3, 7, 3]
>>> lst.reverse()
>>> lst
[3, 7, 3, 1]
>>> lst.index(3)
0
>>> lst.sort()
>>> lst
[1, 3, 3, 7]
>>> lst.remove(3)
>>> lst
[1, 3, 7]
>>> lst.pop()
7
>>> lst
[1, 3]
Usage Explanation
lst.append(item) adds item to the end of lst
lst.count(item) returns the number of times item
occurs in lst
lst.index(item) Returns index of (first occurrence of)
item in lst
lst.pop() Removes and returns the last item in lst
lst.remove(item) Removes (the first occurrence of) item
from lst
lst.reverse(item) Reverses the order of items in lst
lst.sort(item) Sorts the items of lst in increasing
order
Methods append(), remove(), reverse(),
and sort() do not return any value; they, along
with method pop(), modify list lst
Introduction to Computing Using Python by Lj Perkovic
String operators >>> ‘Hello, World!’
‘Hello, World!’
>>> s = ‘rock’
>>> t = ‘climbing’
>>> s == ‘rock’
True
>>> s != t
True
>>> s < t
False
>>> s > t
True
>>> s + t
‘rockclimbing’
>>> s + ‘ ‘ + t
‘rock climbing’
>>> 5 * s
‘rockrockrockrockrock’
>>> 30 * ‘_’
‘______________________________’
>>> ‘o’ in s
True
>>> ‘o’ in t
False
>>> ‘bi’ in t
True
>>> len(t)
8
Usage Explanation
x in s x is a substring of s
x not in s x is not a substring of s
s + t Concatenation of s and t
s * n, n * s Concatenation of n copies of s
s[i] Character at index i of s
len(s) (function) Length of string s
>> help(str)
Help on class str in module builtins:
class str(object)
| str(string[, encoding[, errors]]) -> str
…
To view all operators, use the help() tool
Usage Explanation
s.capitalize() returns a copy of s with first character
capitalized
s.count(target) returns the number of occurences of
target in s
s.find(target) returns the index of the first
occurrence of target in s
s.lower() returns lowercase copy of s
s.replace(old, new) returns copy of s with every
occurrence of old replaced with new
s.split(sep) returns list of substrings of s,
delimited by sep
s.strip() returns copy of s without leading and
trailing whitespace
s.upper() returns lowercase copy of s
Introduction to Computing Using Python by Lj. Perkovic
String methods
Strings are
immutable;
none of the
string methods
modify string
link
Programming Exercises
>>> pairSum([7, 8, 5, 3, 4, 6], 11)
04
13
25
5.20 Write a function intersect() that takes two lists, each containing no duplicate values, and returns a list containing values that are present in both lists (i.e., the intersection of
the two input lists).
>>> intersect([3, 5, 1, 7, 9], [4, 2, 6, 3, 9])
[3, 9]
5.21 Implement the function pair() that takes as input two lists of integers and one integer
and prints the pairs of integers, one from the first input list and the other from the second
input list, that add up to n. Each pair should be printed.
n
>>> pair([2, 3, 4], [5, 7, 9, 12], 9)
27
45
5.22 Implement the function pairSum() that takes as input a list of distinct integers 1st
and an integer n, and prints the indexes of all pairs of values in 1st that sum up to n.
the input list is the same but the target value is 10, then the returned value should be False
because 10 is not the sum of any three numbers in the given list.
>>> subsetSum([5, 4, 10, 20, 15, 19], 38)
True
>>> subsetSum([5, 4, 10, 20, 15, 19], 10)
False
5.31 Write a function subsetSum() that takes as input a list of positive numbers anda
positive number target. Your function should return True if there are three numbers in
the list that add up to target. For example, if the input list is [5, 4, 10, 20, 15, 19]
and target is 38, then True should be returned since 4+ 15+ 19 38. However, if
5.29 Write function lastfirst() that takes one argument-a list of strings of the format
<LastName, FirstName>-and returns a list consisting two lists:
(a) A list of all the first names
(b) A list of all the last names
>>> lastfirst([‘Gerber, Len’, ‘Fox, Kate’, ‘Dunn, Bob’])
[[‘Len’, ‘Kate’, ‘Bob’], [‘Gerber’, ‘Fox’, ‘Dunn’]]
rpmaximum
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