Question

Deliverables

There is one deliverable for this assignment

• hw4.py

Make sure the script obeys all the rules in the Script Requirements page.

Specification

The file has entries like the following

Barnstable,Barnstable,1
Bourne,Barnstable,5
Brewster,Barnstable,9
...

This script should create a dictionary where the county is the key and then total number of cases for the country is the value.

The script should print the name of the county with the highest number of cases along with the total cases.

The script must have 3 functions

• open_file_read
• cases_dictionary_create
• highest_cases

This script must read in a text file with case numbers for all cities in Massachusetts along with their counties.

open_file_read

This function must have the following header

def open_file_read(filename):

It must try to create a file object for reading on the file whose name is given by the parameter filename.

If it is succesfull in creating the file object it should return the object.

If it is cannot create the object it should print an error message and return None.

cases_dictionary_create

This function must have the following header

def cases_dictionary_create(file):

This function reads a file and creates a dictionary where the keys are counties and the values are total cases.

• The function returns this dictionary.

highest_cases

This function must have the following header

def highest_cases(county_cases):

The function

Script for this assignment

Open an a text editor and create the file hw4.py.

You can use the editor built into IDLE or a program like Sublime.

Test Code

Your hw4.py file must contain the following test code at the bottom of the file

filename = input("File name: ")
file = open_file_read(filename)
if file:
        cases = cases_dictionary_create(file)
        max_county, max_cases = highest_cases(cases)
        print(max_county,max_cases)

For this test code to work, you must copy cities_counties_cases.txt to your machine.

To do this use FileZilla to copy the file cities_counties_cases.txt f rom /home/ghoffman/course_files/it117_files into the directory that holds your hw4.py script.

Run the script entering cities_counties_cases.txt when prompted.

You should see

$ ./hw4.py 
File name: cities_counties_cases.txt
Worcester 455

Suggestions

Write this program in a step-by-step fashion using the technique of incremental development.

In other words, write a bit of code, test it, make whatever changes you need to get it working, and go on to the next step.

1. Create the file hw4.py.
   Enter the headers for open_file_read, cases_dictionary_create and highest_cases.
   Under each header write the Python statement pass.
   Run the script.
   Fix any errors you find.
2. Replace the pass statement in open_file_read with the body of the code from your hw2.py.
   Copy the first two lines of the test code into the bottom of the file.
   Run the scrip entering both a real filename and the name of a file that does not exists.
   Fix any errors you find.
3. Remove the pass statement from cases_dictionary_create.
   Create the empty dictionary county_cases,
   Write a for loop that prints every line in the file.
   Copy the next two lines of the test code into your script.
   Run the script entering cities_counties_cases.txt when prompted.
   Fix any errors you find.
4. Remove the print statement.
   You will have to use the split string method on each line in the file to assign values to the variables city, county and cases, but you need to use "," as the argument to split.
   Use either one of the techniques found in Class Exercise 2 or Class Exercise 3 to assign values to the variables.
   Write and assignment statement that converts cases to an integer.
   Print the value of the three variables.
   Run the script.
   Fix any errors you find.
5. Remove the print statement.
   Now you are going to have to create entries in the dictionary county_cases, but this will take some thinking.
   You need to write an if statement that checks whether the value of county is already in the dictionary.
   If it is, you and the value of cases to the current value of cases in the dictionary and store that as the new value for county.
   If it is not already in the dictionary, create a new value entry with county as the key and cases as the value.
   Outside the for loop print the dictionary county_cases.
   Run the script.
   Fix any errors you find.
6. Remove the print statement.
   In it's place write a statement to return county_cases.
   Remove the pass statement from highest_cases.
   In it's place write a for loop that loops through the entries in the dictionary.
   Inside the loop get the value of the current entry and assign it to the variable cases.
   
   Print county and cases For each entry.
   Outside the for loop return two empyy strings.
   If you don't you will get a runtime error when you run the script.
   Add the next line in the test code to the bottom of the script.
   Run the script.
   Fix any errors you find.
7. Now you are going to have to find the county with the highest number of cases.
   You should use the same technique used in Class Exercise 3.
   Above the for loop assign the variable max_cases the value 0 and assign max_county the empty string.
   Remove the print statement inside the for loop.
   Write and if statement that checks whether the value of cases is greater than max_cases.
   If it is, set max_caes to the value of cases and max_county to county. Outside the for loop return max_county and max_cases.
   Copy the last line of the test code into the script.
   Run the script.
   Fix any errors you find.

Answer 1

CODE -

# Function to create a file object for reading on the file whose name is given by the parameter

# and return the file object if successful in creating file object.

def open_file_read(filename):

    # Opening the file

    cases_file = open(filename)

    # Returning the file object if file is opened successfully

    if cases_file:

        return cases_file

    else:

        # Printing error message and returning None if file can't be opened.

        print("File cannot be Opened.")

        return None

# Function to read file and create and return dictionary containing county names and cases

def cases_dictionary_create(file):

    # Creating empty dictionary

    cases_dict = {}

    # Reading file line by line

    for line in file:

        # Seperating city name, county name, and cases from the file which is seperated by comma

        line_list = line.split(",")

        # Adding county name and case to the dictionary if county name is not already in the dictionary

        if line_list[1] not in cases_dict:

            cases_dict[line_list[1]] = int(line_list[2].strip())

        # Adding no. of cases to the cases of the corresponding county if county name is already in the dictionary

        else:

            cases_dict[line_list[1]] += int(line_list[2].strip())

    # Returning the dictionary

    return cases_dict

# Function to find and return county name and cases with highest no. of cases.

def highest_cases(county_cases):

    # Initializing max_county to empty string

    max_county = ""

    # Initializing max_cases to 0

    max_cases = 0

    # Iterating over each county in the dictionary

    for county in county_cases:

        cases = county_cases[county]

        # Checking if no. of cases for current county is greater than max_cases.

        # If yes, assigning current county name to max_county and no. of cases of current county to max_cases

        if cases > max_cases:

            max_county = county

            max_cases = cases

    # Returning name of county and no. of cases of county with max no. of cases

    return max_county, max_cases

# Testing the script.

filename = input("File name: ")

file = open_file_read(filename)

if file:

    cases = cases_dictionary_create(file)

    max_county, max_cases = highest_cases(cases)

    print(max_county,max_cases)

SCREENSHOTS -

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