#!/usr/bin/env python
# coding: utf-8

# # Programming with Python
# #### Stefan Güttel, [guettel.com](http://guettel.com)
# 
# ## Exercises: File I/O

# **Reminder:** To test your solutions, you need to create one or more text files. You can do so in Spyder, Notepad, or any other text editor.

# **Problem 1.** Write a program that loads names of two files. Each file contains integers, one per each line. The program has to print a message describing if the sets of numbers contained in those files are equal, or the first one is a proper subset of the second one, or the second one is a proper subset of the first one, or neither.
# 
# **Hint:** Since the program needs to read from two files, make a function that reads a file into a set and returns that set.

# **Problem 2.** Write a program that loads a name of a text file and reverses the order of its lines (overwriting the original file). You may assume that the file ends with an empty line (i.e., all lines end with a new line character).
# 
# **Hint:** Read the file, line by line, reverse it, and save it.

# **Problem 3.** Write a program that loads an integer `n` and a file name, and then creates a text file with that name containing the [multiplication table](http://en.wikipedia.org/wiki/Multiplication_table) for all numbers between 1 and `abs(n)` (including both of them).
# 
# Save the table in the following format:
# 
#      *  | 1  | 2  | 3  | 4  | 5  
#     ----|----|----|----|----|----
#      1  | 1  | 2  | 3  | 4  | 5  
#      2  | 2  | 4  | 6  | 8  | 10 
#      3  | 3  | 6  | 9  | 12 | 15 
#      4  | 4  | 8  | 12 | 16 | 20 
#      5  | 5  | 10 | 15 | 20 | 25 
# 
# So, a `*` in the top left cell, a horizontal dashed line after the header, and all the numbers should be centered in 2 characters more than is needed to display $n^2$.
# 
# **A note on the purpose of these tables (not part of the problem):** Text formatted as required by this problem can be used in [GFM](http://github.github.com/github-flavored-markdown/) as tables. For example, the above text is displayed like this:
# 
#  *  | 1  | 2  | 3  | 4  | 5  
# ----|----|----|----|----|----
#  1  | 1  | 2  | 3  | 4  | 5  
#  2  | 2  | 4  | 6  | 8  | 10 
#  3  | 3  | 6  | 9  | 12 | 15 
#  4  | 4  | 8  | 12 | 16 | 20 
#  5  | 5  | 10 | 15 | 20 | 25 
#  
# A bit more advanced version is to replace each `"----"` with "`:--:`":
# 
#      *  | 1  | 2  | 3  | 4  | 5  
#     :--:|:--:|:--:|:--:|:--:|:--:
#      1  | 1  | 2  | 3  | 4  | 5  
#      2  | 2  | 4  | 6  | 8  | 10 
#      3  | 3  | 6  | 9  | 12 | 15 
#      4  | 4  | 8  | 12 | 16 | 20 
#      5  | 5  | 10 | 15 | 20 | 25 
# 
# This achieves the centered display of the numbers when processed as GFM:
# 
#  *  | 1  | 2  | 3  | 4  | 5  
# :--:|:--:|:--:|:--:|:--:|:--:
#  1  | 1  | 2  | 3  | 4  | 5  
#  2  | 2  | 4  | 6  | 8  | 10 
#  3  | 3  | 6  | 9  | 12 | 15 
#  4  | 4  | 8  | 12 | 16 | 20 
#  5  | 5  | 10 | 15 | 20 | 25