Programming in Python - Assignment Example

Programming in python SECTION A Question 1 Function menu() is used to provide the options for the application. It is called by the main() function when the program starts. After providing the options to use for the applications, it prompts the user for the digit(s) representing the option they want to use. Eg. "1. Display all the scheduled flights on file". When the user responds with a “1” the value is returned to the main() function and it displays all the scheduled flights after processing in the main() function. Question 2 In the line of code “outfile = open(DATA_FILE, 'a')” the ‘a’ is a parameter that is passed to in-built open() function to mean that any data should be appended to the end of the data file. In other words, add any new stream of text at the end of the already existing text in the data file. Question 3 FLIGHT_NO is a global variable and it represents 0 (zero). It is set/initialized at the beginning of the script and not within any function. It may then be used in any function without declaration and initialization inside the function. Question 4 In the second line in main(), choice = menu(), choice gets its value from the returned value in menu() function. The last line of menu() is “return option”, option being the value entered by a user after they were prompted to enter a number shown on the select menu. After, menu returns the value in variable option; it is then assigned to choice. Question 5 When the program is run and the user enters three, the menu() function return the value (3) and it is assigned to choice thus variable choice now represents 3 in the main() function. Variable choice is then checked using the while loop to ensure it is not equal to 20, 20 represent an exit from system run. Variable choice is then checked using the if – elif control structure, using the “choice == 3” the application prompt for a flight number in the main() function and the calls function displayFlightDetails(infile, flightNumber). The function then displays the flight details for a particular flight number. Question 6 When the program finishes, the value of choice is 20. Before variable choice attains this value, the user is prompted to enter an option. When the user enters 20, the variable choice is assigned with 20 and it checks in the while loop. The condition in the while loop permits continuous execution as long as the value of choice is not equal to 20. If the value is 20, it exits the while loop and the program terminates. Question 7 In the function displayFlightList, the variable splitLine contains an array of values obtained from splitting a particular line of text in the flight.txt. The spaces are used as delimiters to signify the end of one value and start of another. splitLine[ORIGIN] contains the origin of a given flight as stored in the line of text. ORIGIN contains the value 2 which gives the index of the array in which it will pick the value of flight origin. Question 8 Function eval() is used to evaluate some lines of code as a syntactic expression and return a result. In other words it is used to access the python interpreter and its parameters provide the lines of code to be interpreted and the result is then fetched from the from the returned value. It may be used when you need to execute some lines of code as a separate entity of the program and capture the results. Question 9 Python code for displayFlightDetails which calls the displayFlightLineDetails() function def displayFlightDetails(inf, flnumber): print "Details for flight:",flnumber for line in inf: splitLine = string.split(line) if splitLine[FLIGHT_NO] == flnumber: displayFlightLineDetails(line) return Question 10 In displayFlightList (inf), ‘inf’ refers to infile and this is the data that has been obtained from reading the flight.txt file. It contains all the text read from the file and can be accessed line by line. The “for line in inf:” line means that for each line of text in a particularof the data stored in inf, assign it to variable line and process. Question 11 The programming line after the while loop is infile.close(). This file is used to close the flight.txt file which was opened to read the data in it. This is because the open connection as an object is closed using the function close(). Question 12 In function “def displayFlightsFromLocn(inf, givenLocn, givenDay):’ parameter givenDay refers to the number of a given day of this week where Sunday is 1 to Saturday as 7. It gets its value from the main() function after a user is prompted to enter this value as a number between 1-7. The value is then assigned to variable “day” and it is passed to the function once called in main(). Question 13 In function findCheapestFlight(), minPrice has been used to store the value the minimum price in all the flights available. minPrice is first given a price that is more than the maximum anticipated price. Then a comparison of is made between this minPrice and the price of a given flight. If the price of the flight is less than the current minPrice, the value of the price is assigned to minPrice thus is becomes the new minimum. This is done for all the flight prices in the file thus at the end of the comparisons it is certain that the minimum value has been obtained. SECTION C Question 1 For the function calculateCostOfFlight(line) it will take one parameter “line” of data type string. This parameter carries a single line of the flight.txt file content and then line represents the flight details for one flight. The function returns one value “cost” which is extracted from the line. Pseudo code This is the pseudo code for the function calculateCostOfFlight(line) Define function calculateCostOfFlight which takes one parameter line Split the line flight details and get the price Assign the price of the flight to the variable cost. Return cost back to the main() function which called this function Question 2 For the functions findNumberOfFlightsToCity(inf, givenCity), it takes 2 parameters “inf” which is a pointer to the input file and given city which is of data type string. The function returns one value “count” which is an integer and it contains the number of flights that are supposed to have their destination in the city that was passed as a parameter. Pseudo code This is the pseudo code for function findNumberOfFlightsToCity(inf, givenCity): Define function findNumberOfFlightsToCity that take two parameters inf and givenCity Set the count of flights to zero For each line in the flight.txt file: Check if the destination city is same as the value contained in variable givenCity If values match increment count by one Return the value of count back to the main menu Question 3 For function addFlight(dataString), it takes a single parameter which is “dataString” and this is of data type string. The string contains values of the flight details for a given flight e.g. flight number, origin, destination e.t.c. This function does not return any values to the main() function that called is but its main purpose is to open the flight.txt file and append the flight details at the end of the file. Pseudo code The pseudo code for the addFlight(newString) function Define function addFlight that takes one paremeter newString Open the closed flight.txt file in append with mode ‘a’ for appending Write the string and add a new line character to move to the next line. Close the opened file Return null to go back to the main() function. Read More