Question

I’m somewhat new to python. I’m trying to sort through a list of strings and integers. The lists contains some symbols that need to be filtered out (i.e. ro!ad should end up road). Also, they are all on one line separated by a space. So I need to use 2 arguments; one for the input file and then the output file. It should be sorted with numbers first and then the words without the special characters each on a different line. I’ve been looking at loads of list functions but am having some trouble putting this together as I’ve never had to do anything like this. Any takers?

So far I have the basic stuff

#!/usr/bin/python

import sys

try:
  infilename = sys.argv[1] #outfilename = sys.argv[2]
except:
  print "Usage: ",sys.argv[0], "infile outfile"; sys.exit(1)

ifile = open(infilename, 'r')
#ofile = open(outfilename, 'w')
data = ifile.readlines()
r = sorted(data, key=lambda item: (int(item.partition(' ')[0])
                               if item[0].isdigit() else float('inf'), item))
ifile.close()
print '\n'.join(r)
#ofile.writelines(r)
#ofile.close()

The output shows exactly what was in the file but exactly as the file is written and not sorted at all. The goal is to take a file (arg1.txt) and sort it and make a new file (arg2.txt) which will be cmd line variables. I used print in this case to speed up the editing but need to have it write to a file. That’s why the output file areas are commented but feel free to tell me I’m stupid if I screwed that up, too! Thanks for any help!

Answer 1

When you have an issue like this, it’s usually a good idea to check your data at various points throughout the program to make sure it looks the way you want it to. The issue here seems to be in the way you’re reading in the file.

data = ifile.readlines()

is going to read in the entire file as a list of lines. But since all the entries you want to sort are on one line, this list will only have one entry. When you try to sort the list, you’re passing a list of length 1, which is going to just return the same list regardless of what your key function is. Try changing the line to

data = ifile.readlines()[0].split()

You may not even need the key function any more since numbers are placed before letters by default. I don’t see anything in your code to remove special characters though.