csci 127: introduction to computer sciencecsci 127 (hunter) lecture 9 14 april 202019/39 third part:...

CSci 127: Introduction to Computer Science

hunter.cuny.edu/csci

CSci 127 (Hunter) Lecture 9 14 April 2020 1 / 39

Announcements

We are back from Spring Break (and all otherbreaks)There should be no more interruptions in ourschedule

Please refer to the updated schedule

If you have consented to participate in theEducational Psychology study,fill in the 3-question survey after watching allthe videos (link also provided at end oflecture)

Announcements

Today’s Topics

Recap: Functions & Top Down Design

Mapping GIS Data

Random Numbers

Indefinite Loops

Today’s Topics

Mapping GIS Data

Random Numbers

Indefinite Loops

In Pairs or Triples:

What are the formal parameters for the functions?

What is the output of:r = prob4(4,"city")

print("Return: ", r)

What is the output of:r = prob4(2,"university")

What is the output of:r = prob4(4,"city")

What is the output of:r = prob4(2,"university")

Python Tutor

(Demo with pythonTutor)

From Last Time: koalas

http://koalastothemax.com

Process:

Get template → Fill in missing → Test locally → Submit tofrom github → functions → idle3/python3 → Gradescope

The main() is written for you.

Only fill in two functions: average() and setRegion().

Top-Down Design

The last example demonstratestop-down design: breaking intosubproblems, and implementing eachpart separately.

I Break the problem into tasks for a“To Do” list.

I Translate list into function names &inputs/returns.

I Implement the functions, one-by-one.

Excellent approach since you can thentest each part separately before addingit to a large program.

Very common when working with ateam: each has their own functions toimplement and maintain.

Top-Down Design

Write the missing functions for the program:

def main():

tess = setUp() #Returns a purple turtle with pen up.

for i in range(5):

x,y = getInput() #Asks user for two numbers.

markLocation(tess,x,y) #Move tess to (x,y) and stamp.

Write the missing functions for the program:

def main():

for i in range(5):

Group Work: Fill in Missing Pieces

def main():

for i in range(5):

Group Work: Fill in Missing Pieces

1 Write import statements.

import turtle

def main():

for i in range(5):

Third Part: Fill in Missing Pieces

1 Write import statements.

2 Write down new function names and inputs.

import turtle

def setUp():

#FILL IN

def getInput():

#FILL IN

def markLocation(t,x,y):

#FILL IN

def main():

for i in range(5):

Third Part: Fill in Missing Pieces1 Write import statements.

3 Fill in return values.

import turtle

def setUp():

#FILL IN

return(newTurtle)

def getInput():

#FILL IN

return(x,y)

#FILL IN

def main():

for i in range(5):

Third Part: Fill in Missing Pieces1 Write import statements.

3 Fill in return values.

4 Fill in body of functions.

import turtle

def setUp():

newTurtle = turtle.Turtle()newTurtle.penup()return(newTurtle)

def getInput():

x = int(input(’Enter x: ’))y = int(input(’Enter y: ’))return(x,y)

t.goto(x,y)t.stamp()

def main():

for i in range(5):

markLocation(tess,x,y) #Move tess to (x,y) and stamp.CSci 127 (Hunter) Lecture 9 14 April 2020 20 / 39

Write a function that takes a number as an input and prints itscorresponding name.

For example,

I num2string(0) returns: zeroI num2string(1) returns: oneI num2string(2) returns: two

You may assume that only single digits, 0,1,...,9, are given as input.

For example,

I num2string(0) returns: zero

I num2string(1) returns: oneI num2string(2) returns: two

For example,

I num2string(0) returns: zeroI num2string(1) returns: one

I num2string(2) returns: two

For example,

Python Tutor

(On github)

Today’s Topics

Mapping GIS Data

Random Numbers

Indefinite Loops

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:

(Map created by Folium.)

Folium

To use:

import folium

Create a map:

myMap = folium.Map()

Make markers:

newMark = folium.Marker([lat,lon],popup=name)

Add to the map:

newMark.add to(myMap)

Many options to customize background map (“tiles”)and markers.

Folium

To use:

import folium

Create a map:

Make markers:

Add to the map:

Folium

To use:

import folium

Create a map:

Make markers:

Add to the map:

Folium

To use:

import folium

Create a map:

Make markers:

Add to the map:

Folium

To use:

import folium

Create a map:

Make markers:

Add to the map:

(Python program using Folium.)

In Pairs of Triples

Predict which each line of code does:

(example from Folium documentation)

Today’s Topics

Mapping GIS Data

Random Numbers

Indefinite Loops

Python’s random package

Python has a built-in package for generatingpseudo-random numbers.

To use:

import random

Useful command to generate whole numbers:

random.randrange(start,stop,step)

which gives a number chosen randomly fromthe specified range.

Useful command to generate real numbers:

random.random()

which gives a number chosen (uniformly) atrandom from [0.0,1.0).

Very useful for simulations, games, andtesting.

To use:

import random

random.random()

To use:

import random

random.random()

To use:

import random

random.random()

To use:

import random

random.random()

To use:

import random

random.random()

Trinket

(Demo turtlerandom walk)

Today’s Topics

Mapping GIS Data

Random Numbers

Indefinite Loops

CS Survey

Predict what the code will do:

Python Tutor

(Demo with pythonTutor)

Indefinite Loops

Indefinite loops repeat as long as thecondition is true.

Could execute the body of the loopzero times, 10 times, infinite numberof times.

The condition determines how manytimes.

Very useful for checking input,simulations, and games.

More details next lecture...

Indefinite Loops

Top-down design: breaking into subproblems, andimplementing each part separately.

Excellent approach: can then test each partseparately before adding it to a large program.

When possible, design so that your code is flexibleto be reused (“code reuse”).

Introduced a Python library, Folium for creatinginteractive HTML maps.

Introduced while loops for repeating commandsfor an indefinite number of times.

Practice Quiz & Final Questions

Lightning rounds:

I write as much you can for 60 seconds;I followed by answer; andI repeat.

Past exams are on the webpage (under Final Exam Information).

Theme: Functions & Top-Down Design (Summer 18, #7 & #5).

Lightning rounds:I write as much you can for 60 seconds;

I followed by answer; andI repeat.

Lightning rounds:I write as much you can for 60 seconds;I followed by answer; and

I repeat.

Lightning rounds:I write as much you can for 60 seconds;I followed by answer; andI repeat.

Educational Psychology Study

If you have consented to participate in theEducational Psychology study,please fill in the 3-question survey

Thank you for your participation!!!

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