Sorting Alphabetically and Numerically

Question

f = open(document) #this will open the selected class data
swag = [f.readline(),f.readline(),f.readline(),f.readline(),f.readline(),f.readline()] #need to make go on for amount of line

viewfile = input("Do you wish to view the results?")#This will determine whether or not the user wishes to view the results
if viewfile == 'yes': #If the users input equals yes, the program will continue
order = input("What order do you wish to view to answers? (Alphabetical)") #This will determine whether or not to order the results in alphabetical order
if order == 'Alphabetical' or 'alphabetical':
    print(sorted(swag))
if order == 'Top' or 'top':
    print(sorted(swag, key=int))

The document reads as

John : 1
Ben : 2
Josh : 3

How would I go about ordering these into numerical order, such as descending?

`if x == y or z` does not do what you think it does. Also, what if the file has a different number of lines? Also, what would be the result of `int("John : 1")`? — tobias_k, Dec 03 '15 at 11:30
`[f.readline(),f.readline(),..]` is a terrible way to read a file into an array. Use a loop, Luke, use a loop! — deceze, Dec 03 '15 at 11:31
Your code has multiple issues. I recommend taking a look at the [official Python tutorial](https://docs.python.org/3.4/tutorial/index.html). — TigerhawkT3, Dec 03 '15 at 11:32
@tobias_k *Use the existing API, Luke* would be the next lesson... :) — deceze, Dec 03 '15 at 11:33

Burhan Khalid · Answer 1 · 2015-12-03T11:35:56.537

1

You have to sort by the numerical value, and then whatever result you get, simply reverse it to reverse the order.

The key here is to sort by the right thing which you need to do by defining a function for the key argument to sorted.

Here the function is a lambda, which simply return the numeric part of the string to be sorted by; which will return it in ascending order.

To reverse the order, simply reverse the list.

with open(document) as d:
   swag = [line.strip() for line in d if line.strip()]

by_number = sorted(swag, key=lambda x: int(x.split(':')[1]))
descending = by_number[::-1]

edited Dec 03 '15 at 11:35

answered Dec 03 '15 at 11:34

Burhan Khalid

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You could use `sorted(..., reverse=True)` – tobias_k Dec 03 '15 at 11:34
Maybe it is also interesting to state: `by_name = sorted(swag, key=lambda x: x.split(':')[0])` – Tulio Casagrande Dec 03 '15 at 11:40

Mike Müller · Answer 2 · 2015-12-03T11:44:09.977

1

You need to split each line at the :. Remove white space from the names and convert the number into an integer (or float if you have). Skip empty lines.

with open(document) as fobj:
    swag = []
    for line in fobj:
        if not line.strip():
            continue
        name, number_string = line.split(':')
        swag.append((name.strip(), int(number_string)))

Sorting is straight forward:

by_name = sorted(swag)
by_number = sorted(swag, key=lambda x: x[1])
by_number_descending = sorted(swag, key=lambda x: x[1], reverse=True)

Variation

Use itemgetter:

from operator import itemgetter

by_number_descending = sorted(swag, key=itemgetter(1), reverse=True)

edited Dec 03 '15 at 11:44

answered Dec 03 '15 at 11:38

Mike Müller

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This will break if there are blank lines in the file. – Burhan Khalid Dec 03 '15 at 11:43
@BurhanKhalid Fixed this. – Mike Müller Dec 03 '15 at 11:45

Sorting Alphabetically and Numerically

2 Answers2

Variation