CSci 127: Introduction to Computer Science

hunter.cuny.edu/csci

CSci 127 (Hunter) Lecture 10 9 April 2019 1 / 36

Announcements

Postponed until next week:CS Survey: Anna WhitneyGoogle Storage Infrastructure Team

Instead: Final Exam ReviewExtra Handout: fall exam(similar, but due to typos, not identical toexam given)

Announcements

Postponed until next week:CS Survey: Anna WhitneyGoogle Storage Infrastructure Team

Instead: Final Exam ReviewExtra Handout: fall exam(similar, but due to typos, not identical toexam given)

Today’s Topics

Recap: Folium

Indefinite loops

Design Patterns: Max (Min)

Final Exam Overview

Today’s Topics

Recap: Folium

Indefinite loops

Final Exam Overview

In Pairs or Triples:What does this code do?

Folium example

What does this code do?

Folium example

What does this code do?

Folium

A module for making HTML maps.

It’s a Python interface to the popularleaflet.js.

Outputs .html files which you can open in abrowser.

An extra step:

Write → Run → Open .htmlcode. program. in browser.

Folium

An extra step:

Folium

An extra step:

Folium

An extra step:

Folium

An extra step:

Today’s Topics

Recap: Folium

Indefinite loops

Python Recap

In Pairs or Triples:

Write a function that asks a user for number after 2000 but before2018. The function should repeatedly ask the user for a number untilthey enter one within the range and return the number.

CodingWrite a function that asks a user for number after 2000 but before2018. The function should repeatedly ask the user for a number untilthey enter one within the range and return the number..

CodingWrite a function that asks a user for number after 2000 but before2018. The function should repeatedly ask the user for a number untilthey enter one within the range and return the number.

def getYear():

return(num)

def getYear():

num = 0

return(num)

def getYear():

num = 0

while num <= 2000 or num >= 2018:

return(num)

def getYear():

num = 0

while num <= 2000 or num >= 2018:

num = int(input(’Enter a number > 2000 & < 2018’))

return(num)

Indefinite Loops

Indefinite loops repeat as long asthe condition is true.

Could execute the body of theloop zero times, 10 times, infinitenumber of times.

The condition determines howmany times.

Very useful for checking input,simulations, and games.

Indefinite Loops

From Last Time: Design Challenge

Collect all five stars (locations randomly generated):

Possible approaches:

I Randomly wander until all 5 collected, orI Start in one corner, and systematically visit every point.

Input: The map of the ‘world.’

Output: Time taken and/or locations of the 5 stars.

How to store locations? Use numpy array with -1 everywhere.

Possible algorithms: while numStars < 5:

I Move forward.I If wall, mark 0 in map, randomly turn left or right.I If star, mark 1 in map and add 1 to numStars.I Otherwise, mark 2 in map that it’s an empty square.

I Randomly wander until all 5 collected, or

I Start in one corner, and systematically visit every point.

I Move forward.

I If wall, mark 0 in map, randomly turn left or right.I If star, mark 1 in map and add 1 to numStars.I Otherwise, mark 2 in map that it’s an empty square.

I Move forward.I If wall, mark 0 in map, randomly turn left or right.

I If star, mark 1 in map and add 1 to numStars.I Otherwise, mark 2 in map that it’s an empty square.

I Move forward.I If wall, mark 0 in map, randomly turn left or right.I If star, mark 1 in map and add 1 to numStars.

I Otherwise, mark 2 in map that it’s an empty square.

In Pairs or Triples

Predict what this code does:

Trinket Demo

(Demo with trinket)

Today’s Topics

Recap: Folium

Indefinite loops

Python Recap

Design Patterns

A design pattern is a standard algorithmor approach for solving a commonproblem.

The pattern is independent of theprogramming language.

Can think of as a master recipe, withvariations for different situations.

Design Patterns

Predict what the code will do:

Python Tutor

(Demo with pythonTutor)

Max Design Pattern

Set a variable to the smallest value.

Loop through the list,

If the current number is larger,update your variable.

Print/return the largest number found.

Similar idea works for finding theminimum value.

Max Design Pattern

Answer the following questions on your lecture slip:

Of the students in the room,

Whose name comes first alphabetically?

Whose name comes last alphabetically?

Is there someone in the room with your initials?

Design a program that takes a CSV file and a set of initials:

Whose name comes first alphabetically?

Whose name comes last alphabetically?

Is there someone in the room with your initials?

Design Question: Find first alphabetically

In Pandas, lovely built-in functions:

I df.sort values(’First Name’) andI df[’First Name’].min()

What if you don’t have a CSV and DataFrame, or data not ordered?

In Pandas, lovely built-in functions:I df.sort values(’First Name’) andI df[’First Name’].min()

Useful Design Pattern: min/maxI Set a variable to worst value (i.e. maxN = 0 or first = "ZZ").I For each item, X, in the list:

F Compare X to your variable.F If better, update your variable to be X.

I Print/return X.

Useful Design Pattern: min/max

I Set a variable to worst value (i.e. maxN = 0 or first = "ZZ").I For each item, X, in the list:

I Print/return X.

Useful Design Pattern: min/maxI Set a variable to worst value (i.e. maxN = 0 or first = "ZZ").

I For each item, X, in the list:F Compare X to your variable.F If better, update your variable to be X.

I Print/return X.

F Compare X to your variable.

F If better, update your variable to be X.

I Print/return X.

Design Question: Find Matching Initials

How do we stop, if we find a match?

Change the loop to be indefinite (i.e. while loop):I Set a variable to found = FalseI while there are items in the list and not found

F If item matches your value, set found = True

I Print/return value.

Change the loop to be indefinite (i.e. while loop):I Set a variable to found = False

I while there are items in the list and not foundF If item matches your value, set found = True

Today’s Topics

Recap: Folium

Indefinite loops

Final Exam Overview

On lecture slip, write down a topic you wish wehad spent more time (and why).

Quick recap of a Python library, Folium forcreating interactive HTML maps.

More details on while loops for repeatingcommands for an indefinite number of times.

Introduced the max design pattern.

Pass your lecture slips to the aisles for the UTAsto collect.

Final Overview: Format

The exam is 2 hours long.

There are 4 different versions to discourage copying.

It is on paper. No use of computers, phones, etc. allowed.

You may have 1 piece of 8.5” x 11” piece of paper.I With notes, examples, programs: what will help you on the exam.I No origami– it’s distracting to others taking the exam.I Best if you design/write yours since excellent way to study.

The exam format:I 10 questions, each worth 10 points.I Questions correspond to the course topics, and are variations on the

programming assignments, lab exercises, and lecture design challenges.I Style of questions: what does the code do? short answer, write

functions, top down design, & write complete programs.I More on logistics after spring break.

Past exams available on webpage (includes answer keys).

You may have 1 piece of 8.5” x 11” piece of paper.

I With notes, examples, programs: what will help you on the exam.I No origami– it’s distracting to others taking the exam.I Best if you design/write yours since excellent way to study.

You may have 1 piece of 8.5” x 11” piece of paper.I With notes, examples, programs: what will help you on the exam.

I No origami– it’s distracting to others taking the exam.I Best if you design/write yours since excellent way to study.

You may have 1 piece of 8.5” x 11” piece of paper.I With notes, examples, programs: what will help you on the exam.I No origami– it’s distracting to others taking the exam.

I Best if you design/write yours since excellent way to study.

The exam format:

I 10 questions, each worth 10 points.I Questions correspond to the course topics, and are variations on the

The exam format:I 10 questions, each worth 10 points.

I Questions correspond to the course topics, and are variations on theprogramming assignments, lab exercises, and lecture design challenges.

I Style of questions: what does the code do? short answer, writefunctions, top down design, & write complete programs.

I More on logistics after spring break.

functions, top down design, & write complete programs.

I More on logistics after spring break.

Exam from Last Semester

Final Exam, Version 3

CSci 127: Introduction to Computer Science

Hunter College, City University of New York

19 December 2018

Exam Rules

• Show all your work. Your grade will be based on the work shown.

• The exam is closed book and closed notes with the exception of an 8 1/2” x 11” piece of paperfilled with notes, programs, etc.

• When taking the exam, you may have with you pens and pencils, and your note sheet.

• You may not use a computer, calculator, tablet, smart watch, or other electronic device.

• Do not open this exam until instructed to do so.

Hunter College regards acts of academic dishonesty (e.g., plagiarism, cheating on examinations,obtaining unfair advantage, and falsification of records and o�cial documents) as serious o↵ensesagainst the values of intellectual honesty. The College is committed to enforcing the CUNY Policyon Academic Integrity and will pursue cases of academic dishonesty according to the Hunter CollegeAcademic Integrity Procedures.

I understand that all cases of academic dishonesty will be reported to the Dean of Students andwill result in sanctions.

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