Index Sort

# In-memory Database Index Sort Demo program
# Written on 05/13/2014 by Darryl Medley for Coding 101 on the TWiT network

# Generic String List print routine
def printList(nmList):
    for rec in nmList:
        print ','.join(rec)   # ','.join converts each sub-list into a comma-delimited string

# Begin main program
print "Coding 101 In-memory Database Index Sort Demo Program\n"
fname = "./name_list.txt"
try:
    # hard-coded version of what is normally read from a file
    infoList = ["padre, 30, 90000","Shannon, 21, 93000","Darryl, 50, 93000","Timmy, 9, 92000"]

# Activate this code to read the list from the name_list.txt file used for the ReadSortWrite.py program
##    with open(fname, "r") as nameListFile:  # open the text file to read
##        # Read the file into a Python list. Each line in the file becomes a
##        # string element in the list. .splitlines() removes the \n (newline)
##        # character from the end of each line and filter(lamda...) skips blank lines
##        infoList = filter(lambda r : r != '',nameListFile.read().splitlines())

except:
    print "Error: File",fname,"does not exist"
else:
    # Convert each comma-delimited string in the list into a sub-list
    # and remove any leading and trailing blanks (whitespace)
    infoList = [[fld.strip() for fld in s.split(",")] for s in infoList]

    # Create index lists for each field we want to sort by. Each index list is a list of
    # two-element sub-lists where the first element is the field we are sorting by (the "key")
    # and the second element is the index # of the entry in main list the key is from.
    #
    # Make the Name index upper case so it case-insensitive
    nameIdxLst = sorted([[fld[0].upper(), i] for i, fld in enumerate(infoList)])
    # Convert the Age to a number so values like 9 sort less than 10
    ageIdxLst = sorted([[int(fld[1]), i] for i, fld in enumerate(infoList)])
    # Since Zipcodes are so common we append the name to the key to subsort by name
    zipIdxLst = sorted([[fld[2]+fld[0], i] for i, fld in enumerate(infoList)])

    print "Unsorted List (Name, Age, Zipcode):"
    printList(infoList)   # call our list print function defined above

    # Print the main list sorted 3 different ways side-by-side using our index lists
    print "\nSorted Lists:\n"
    print "{:20}{:20}{:20}".format("By Name:","By Age:","By Zipcode:")
    for i in range(len(infoList)):
        print "{:20}{:20}{:20}".format(','.join(infoList[nameIdxLst[i][1]]),
                                       ','.join(infoList[ageIdxLst[i][1]]),
                                       ','.join(infoList[zipIdxLst[i][1]]))

raw_input("\n(press Enter to close)")