# Python programming assignment 2 Essay Example

• Category:
Logic & Programming
• Document type:
Math Problem
• Level:
• Page:
3
• Words:
1643

## SECTION A

1. SHOE_STYLE

Altering the value of SHOE_STYLE in the order system to 6 has a lot of impact in the system. The constant used to access order detail in the list is changed. Lists usually starts at value zero i.e [0, 1, 2, 3, 4, 5]. When the value of SHOE_STYLE is changed to 6, the program terminates when a user chooses option 5 because the range is exceeded.

1. file: size = eval(string.split(line)[SIZE])

In this expression, the built in function eval() is used to execute and return a result of evaluation of the size of the list. It is for this purpose that the expression is user to give the size of the item.

1. Purpose of the readorders(inf) function

#The list of lines in inf is converted to variable orderlist, this is a declaration.

orderlist = list(string.split(line) for line in inf)

#a variable convertedlist is declared and defined as empty list.

convertedlist=[]

#for loop is used to iterate the ordelist and append items in ordelist to the convertedlist

for element in orderlist:

convertedlist.append([element[0],element[1],element[2],eval(element[3]),eval(element[4]), element[5]])

return convertedlist

1. Replacing the code convertedorderlist = readorders(inf) in the function mysort(): with the code convertedorderlist = list(string.split(line) for line in inf).

The program runs well and sorts the list well. The output is correct.

1. Sorting by ShoeStyle

Program runs well and sorts the list well. The output is correct.

1. Sorting by price

Program runs well and gives the right output. The output is correct.

1. Use of constants

In the function readorders, the code can be changed to use constants in place of literal at

convertedlist.append([element[0],element[1],element[2],eval(element[3]),eval(element[4]),element[5]). This is replaced with constants as convertedlist.append( i in range inf)

1. Use of result in comparevalsGT.

result = list1[skey] > list2[skey]

return result

This expression uses result to hold values for list where first item is greater that second item.

1. Definition of writeout function and improvement of readability

writeout function makes use outf.write(‘n’) to improve readability. Each of the items is therefore printed in new line.

1. infile.seek(0) line

This line (infile.seek(0)) is meant to reset the items in file orders.txt items after a every sort action, removing this line leaves the sorted items with the previous order, hence the subsequent sorting will not be correct.

1. The function insertionsortorders().

The function uses the concept of insertion sort to sort the details of the file in orders.txt. In this function a unique key with a value is assigned to every line in the file.

This is achieved in the following order:-

Function insertionsortordersis() definition

Variable orderList declared as converted( in the function readorders(inf))

Variable sortedList declared as a list of the orderList

For loop used to loop through sortedlist from the beginning to the end of list.

While loop used to loop through items,

Evaluate the items

Re-arrange the items in the list based on the criterion. Re-arrangement is done by inserting the current item to the previous item location based on position.

Print “Orders insertion sorted by item at position” in new line

Write in a new file the final output in the sorted list for output.

#Finction definition

#tList1 declared as variable to hold list details

tList1= (string.split(line) for line in inf)

#orderList is assisgned the list(tList1) values

orderlist = list(tList1)

#
convertedlist is set as emplty list

convertedlist=[]

## SECTION B

Reflection:

1. Code examination

• In an iteration both for loop and while loop can be nested together to give optimum use of lines of codes.

• infile.seek(0) is a n expression used to reset file pointer

• Insertion sort and bubble sort can be used to give sorted list result output. Both do the same function but differently

• A function can have more than one arguments e.g ordersort(inf, skey, outf)

• eval() is an inbuilt function used in evaluating options before executions.

1. The function comparevalsGT ()

comparevalsGT has been used to get the greater item in the list between two items in comparison for appropriate insertion in the rightful position. This facilitates sorting is by a given criteria.

# comparevalsGT function definition

def comparevalsGT(listOrders, skey, posn1, posn2):

#declare first item in the list

list1=listOrders[posn1]

#declare second item in the list

list2=listOrders[posn2]

# reset the first item as result if it is greater than second item

result = list1[skey] > list2[skey]

return result

1. The function swapListPositions(sList, posn1, posn2).

# function definition

def swapListPositions(sList, posn1, posn2):

#declare list of items on first position

tmp = sList[posn1]

#swap items in first position with items in second position

sList[posn1]=sList[posn2]

sList[posn2]=tmp

#return result

The swapListPositions function is used to swap items from one position to the other.

The function is only used with bubble sort. Insertion sort program do not use this function.

1. The function mysort().

The function mysort has used the sort in-built function sorted(list); this is a method to sort items in a list. When this in-built function sorted(list) is called, it gives a result of a sorted list.

Arguments in sorted.

The argument in sorted provides the decision function directing sorted() on how to decide on the order between any two items in the list.

Lambda function

Lambda is a construct used to save memory and number of lines of codes. It makes codes simple and smaller.

1. The function insertionsortorders().

#function definition

def insertionsortorders(inf, skey, outf):

# assign variable orderList the list in readorders(inf)

#assign variable sortedList the list in orderList

sortedList = list(orderList)

# use for loop to iterate through sortedList

for index1 in range(1,len(sortedList)):

index2 = index1

currNum = sortedList[index1][skey]

#use while loop to repeat the iteration until the list is sorted

while (currNum < sortedList[index2 — 1][skey] and index2 != 0):

index2 = index2-1

sortedList.insert (index2, sortedList.pop(index1))

#write the sorted result

outf.write(‘n’+»Record insertion sorted by team at position «+ str(skey+1)+’:nn’)

writeout(sortedList, outf, skey) #write sorted orders to given output file

return sortedList

1. ## The insertion sort achieved in the Book Shop Management system designed using python programming language is illustrated below. The several sorting functions used have been extracted. The function provided in the orders system such as comparevalsGT, swapListPositions and readorders have been renamed and used appropriately in the book shop management system to attain suitable sorting result.

tList1= (string.split(line) for line in inf)

bookList = list(tList1)#list of lines

convertedlist=[]

for element in bookList: convertedlist.append([element[0],element[1],element[2],eval(element[3]),eval(element[4]),element[5]])

return convertedlist

# this is a function to compare on any given key -e.g. price, size, style etc.

#define comparebooksvalBGfunction

def comparebooksvalBG(clistBooks, skey, posn1, posn2):

#declare list1 as the first item in the list

list1=clistBooks[posn1]

#declare list2 as the second item in the list

list2=clistBooks[posn2]

#compare and give a result of the result of comparison

result = list1[skey] > list2[skey]

return result

def insertionsortbooks(inf, skey, outf):

sortedList = list(bookList)

for index1 in range(1,len(sortedList)):

index2 = index1

currNum = sortedList[index1][skey]

while (currNum < sortedList[index2 — 1][skey] and index2 != 0):

index2 = index2-1

sortedList.insert (index2, sortedList.pop(index1))

outf.write(‘n’+»Record insertion sorted by item at position «+ str(skey+1)+’:nn’)

writeout(sortedList, outf, skey) #write sorted orders to given outputfile

return sortedList

# sort a given file of strings, sorting on key position, save output to newfile

def booksort(inf, skey, outf):

convertedbookList = list(string.split(line) for line in inf)

#use in-built sort function to sort on the skey index of the list

newbookList = sorted(convertedbookList, key=lambda num: num[skey])

writeout(newbookList, outf, skey) #output the new sorted orders to a file

def writeout(bookList, outf, keyposn):

#print «Sorted order list follows » #testing

#print newbookList

#print «Done»

outf.write(«books sorted by item at position «+ str(keyposn+1)+’:n’+’n’)

for books in bookList:

#print order details formatted

outf.write(books[0]+» «+books[1]+» «+books[2]+» «+str(books[3])+ » \$»+str(books[4])+» «+books[5])

#write new line

outf.write(‘n’)

def main():

# Open file and display menu

infile = open(DATA_FILE, ‘r’)

while choice != 20:

if choice == 1:

displayFile(infile)

elif choice == 9:

sortkey = raw_input(«Enter sort key (BookType(1) BookSubject(2) BookCode(3) BookPages(4) BookPrice(5) BookShop(6)): «)

sortkeyval = eval(sortkey) — 1 # align sort key with index 0..5

newfilename = raw_input(«Enter file name to save sorted Books in :»)

print «opening file «, newfilename

sortedfile = open(newfilename, «w»)

booksort(infile,sortkeyval,sortedfile)

print «now doing insertion sort»

infile.seek(0) #reset file pointer

insertionsortbooks(infile,sortkeyval,sortedfile)

sortedfile.close()

print «Wrong number chosen — try again»

# Reset file reading position to start of file and display menu again

infile.seek(0)

# Close file and end program

infile.close()

print «End of program»

# Execute main function

## SECTION C

Bubble sort

Pseudo code

Start = first item on list

Evaluate the first two items

If first > second,

For each pair of adjacent elements, continue to the end of the list.

While swap occur on the last pass, Repeat.

#function definitin

def bubble_sort(teamList)

#set sort_List as list in teamList

sort_List = list (teamList)

# Evaluate the items in the list

for i in range(len(sort_List) -1):

for j in range (len(sort_List) — (i + 1)):

if (sort_List [j] > sort_List [j + 1]):

#swap the position in sorting

swapLocations (sort_List, j, j + 1)

return sort_List

Documentation

This is a python program designed to process the orders in a book shop. It is a sample project of a book shop management system. The program works with data in a text file called data.txt.

The details of the data in the text file are as follows

 Book Type Book Code Book Pages Book Cost Book Shop Dictionary Business Periodical Business Dictionary Computing Periodical Computing

Data types

There are data types used majorly in the program. These are:-

1. Basic data types such as Int, Float and string

2. Containers such as lists

3. Constructs such as Lambda

4. Arrays and pointers

Built-in functions

The Built-in functions used are:-

append()

sorted()

Iteration

There is basic loop such as for, and if.

Advanced iteration has also been used where both if, for and while loop are used, in other cases two lopps has been nested together to achieve the best result.