add asort.py script to sort items automatically.

auto_sort/README.md

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+# Introduction
+`asort.py` is a very simple python3 script that aims to make sure items in the README file of the repo [Awesome-Linux-Software](https://github.com/VoLuong/Awesome-Linux-Software) are sorted alphabetically.
+
+This script only sorts items in the following topics for now (items between topic Applications and topic Setup):
+- Applications
+- Command Line Utilities
+- Desktop Environments
+- Display Managers
+- Window Managers
+
+# Usage
+1. Add items to corresponding topics, don't worry about the order of those items.
+1. Make sure you've installed python3 environment on your system.
+1. Open a terminal, type `python3 asort.py` to run this script. After that, you'll get a new README file with all the items in the above topics being sorted alphabetically.
+
+[test screenshot](./test.png)
+
+# License
+MIT License.

auto_sort/asort.py

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+#!/usr/bin/env python3
+# -*-coding: utf-8-*-
+# Author : Christopher L
+# Blog   : http://blog.chriscabin.com
+# GitHub : https://www.github.com/chrisleegit
+# File   : asort.py
+# Date   : 2016/08/22 11:12
+# Version: 0.1
+# Description: A very simple python script that can sort items alphabetically.
+
+import os
+import shutil
+
+
+README_FILE = '../README.md'
+TEMP_FILE = 'temp.md'
+
+# only works for those items between BEGIN and END.
+BEGIN = '## Applications'
+END = '## Setup'
+
+
+def main():
+    global README_FILE
+
+    # make sure the script can find file: README.md
+    README_FILE = os.path.abspath(README_FILE)
+
+    if not os.path.exists(README_FILE):
+        print('Error: no such file or directory: {}'.format(README_FILE))
+        exit(1)
+
+    sort_enable = False
+    items = list()
+
+    print('Loading file: {}'.format(README_FILE))
+
+    # read file: README.md
+    with open(README_FILE) as infile, open(TEMP_FILE, 'w') as outfile:
+        # process each line
+        for line in infile:
+            if not sort_enable and BEGIN in line:
+                sort_enable = True
+
+            # if sort_enable and END in line:
+            #     sort_enable = False
+
+            if sort_enable:
+                line = line.strip()
+
+                # each item starts with a character '-' (maybe '*' and '+')
+                if line.startswith(('-', '*', '+')):
+                    items.append(line)
+                elif line.startswith('#'):
+                    sort_enable = False if END in line else True
+
+                    # when we meet the next header, we should stop adding new item to the list.
+                    for item in sorted(items, key=lambda x: x.upper()):
+                        # write the ordered list to the temporary file.
+                        print(item, file=outfile)
+                    print('', file=outfile)
+                    items.clear()
+
+                    # remember to put the next header in the temporary file.
+                    print(line, file=outfile)
+                else:
+                    print(line, end='', file=outfile)
+            else:
+                print(line, end='', file=outfile)
+
+    print('Replace the original file: README.md')
+    shutil.move(TEMP_FILE, README_FILE)
+
+
+if __name__ == '__main__':
+    main()
+