Chapter 7, Problem 13PE

Program Plan Intro

Calculate day number corresponding to a date

Program plan:

• Define the function “isLeapYear()”,
  • Check whether the year is not divisible by "4",
    • If it is true, return “False”.
    • Otherwise, check whether the year is divisible by "100",
      • If it is true, check whether the year is divisible by "400",
        • If it is true, return “True”.
        • Otherwise, return “False”.
      • Otherwise, return “True”.
• Define the function “verifyDate()”,
  • Check whether either a month is greater than "12" or day is greater than "31",
  • If it is true, return “False”.
    • Otherwise, Check whether day is less than or equal to "28",
    • If the condition is “True”, return “True”.
    • Otherwise, check whether month is "2" and day is "29",
    • If it is “True” check whether the return value from “isLeapYear()” is “False”,
      • If “True”, return “False”.
      • Otherwise, return “True”.
    • Otherwise, check whether day is equal to “31”,
      • If “True”, Check whether month is either "2" or "4" or "6" or "11",
        • If “True” return “False”.
        • Otherwise, return “True”.
      • Otherwise, return “True”.
• Define the function “main()”,
  • Get the date from the user.
  • Assign month, day, and year by splitting the date by "/" using “split()” method
  • Typecast month, day, and year to “int” type.
  • Check whether the value return from “verifyDate()” is “False”,
    • If it is “True”, print invalid.
    • Otherwise, calculate the number of day using the formula.
    • Check whether the month is “2”,
      • If “True”, check the value return from “isLeapYear()” method is “True”,
      • If “True”, calculate the day number using the formula.
      • Otherwise, calculate the day number using another formula.
    • Otherwise, calculate the day number using the given formula.
  • Print the numeric value for the date.
• Call the function “main()”.

Program Description Answer

This Python program accepts a date as month/ day /year format, and verifies that it is a valid date, and then calculates the corresponding day number.

Explanation of Solution

Program:

File name: “Number.py”

#Define the function isLeapYear()

def isLeapYear(y):

    #Check whether the year is not divisible by "4"

    if (y % 4) != 0:

        #Return false

        return False

    #Otherwise

    else:

        #Check whether the year is divisible by "100"

        if (y % 100) == 0:

            #Check whether the year is divisible by "400"

            if (y % 400) ==0:

                #Return true

                return True

            #Otherwise

            else:

                #Return false

                return False

        #Otherwise

        else:

            #Return true

            return True

#Define the function verifyDate()

def verifyDate(mon, d, yr):

    '''Check whether either a month is greater than "12" or day is gretaer than "31"'''

    if mon > 12 or d > 31:

        #Return "False"

        return False

    #Otherwise

    else:

        #Check whether day is less than or equal to "28"

        if d <= 28:

            #Return True

            return True

        #Check whether month is "2" and day is "29"

        elif mon == 2 and d == 29:

            #Check whether the return value is false

            if isLeapYear(yr) == False:

                #Return "False"

                return False

            #Otherwise

            else:

                #Return "True"

                return True

        #Check whether day is "31"

        elif d == 31:

            #Check whether month is either "2" or "4" or "6" or "11"

            if mon == 2 or 4 or 6 or 11:

                #Return "False"

                return False

            #Otherwise

            else:

                #Return True

                return True

        #Otherwise

        else:

            #Return True

            return True

#Define the function main()

def main():

    #Get the date from the user

    date=eval(input("Enter date"))

    #Initialize the value

    dayNum=0

    '''Assign month, day, and year by splitting the date by "/" using split() method'''

    month_Str, day_Str, year_Str = date.split("/")

    #Typecast month to int type

    mon = int(month_Str)

    #Typecast day to int type

    d = int(day_Str)

    #Typecast year to int type

    yr = int(year_Str)

    #Check whether the return value is false

    if verifyDate(mon, d, yr) == False:

        #Print invalid

        print("This date is invalid.")

    #Otherwise

    else:

        #Calculate the number of a day

        dayNum = 31 * (mon - 1) + d

        #Check whether month is "2"

        if mon == 2:

            #Check whether the return value is True

            if isLeapYear(yr) == True:

                #Calculate the day numbber

                dayNum = dayNum - (4 * (mon) + 23)//10 + 1

            #Otherwise

            else:

                #Calculate the day number

                dayNum = dayNum - (4 * (mon) + 23)//10

        #Otherwise

        else:

            #Calculate day number

            dayNum = 31 * (mon - 1) + d

    #Print the day number

    print("The numeric value of this date is {}.".format(dayNum))

#Call the function main()

main()

Sample Output

Output:

Enter date'2/28/2001'

The numeric value of this date is 56.

Additional Output:

Enter date'05/25/1885'

The numeric value of this date is 149.