#!/usr/bin/python

# P2PU - Python Programming - Chapter 5 - Datatypes
# Chapter 8 - Lists
print 'Python for Informatics - Chapter 8: Lists'

# Exercise 8.1
print '\n# Exercise 8.1\n'
def chop(t):
    del t[0]
    del t[len(t)-1]
    return None
def middle(t):
    return t[1:len(t)-1]
letters = ['a', 'b', 'c', 'd', 'e', 'f']
print 'list before function chop:', letters
chop(letters)
print 'list after function chop :', letters
print
letters = ['a', 'b', 'c', 'd', 'e', 'f']
print 'original list before function middle:', letters
nletters = middle(letters)
print 'original list after function middle :', letters
print 'new list after function middle      :', nletters


# Exercise 8.2
inp = raw_input('Press <enter> to continue')
print '\n# Exercise 8.2\n'
fname =  'mbox.txt'
try:
    ffile = open(fname)
except:
    print 'File', fname, 'cannot be opened!'
    exit()
for line in ffile:
    words = line.split()
    # if it's an empty line continue
    # if there are less then 3 words continue
    if len(words) < 3: continue
    if words[0] != 'From': continue
    print words[2]

# Exercise 8.3
inp = raw_input('Press <enter> to continue')
print '\n# Exercise 8.3\n'
fname =  'mbox.txt'
try:
    ffile = open(fname)
except:
    print 'File', fname, 'cannot be opened!'
    exit()
for line in ffile:
    words = line.split()
    # assignment says use and but looks easier with or
    if len(words) < 3 or words[0] != 'From': continue
    print words[2]

# Exercise 8.4
inp = raw_input('Press <enter> to continue')
print '\n# Exercise 8.4\n'
fname =  'romeo.txt'
wordlist = list()
try:
    ffile = open(fname)
except:
    print 'File', fname, 'cannot be opened!'
    exit()
for line in ffile:
    words = line.split()
    for word in words:
        if word in wordlist: continue
        wordlist.append(word)
wordlist.sort()
print wordlist

# Exercise 8.5
inp = raw_input('Press <enter> to continue')
print '\n# Exercise 8.5\n'
fname =  'mbox-short.txt'
count = 0
try:
    ffile = open(fname)
except:
    print 'File', fname, 'cannot be opened!'
    exit()
for line in ffile:
    words = line.split()
    # assignment says use and but looks easier with or
    if len(words) < 3 or words[0] != 'From': continue
    print words[1]
    count += 1
print 'There were %d lines in the file with From as the first word.' % count

# Exercise 8.6
inp = raw_input('Press <enter> to continue')
print '\n# Exercise 8.6\n'
numlist = list()
while True:
  number = raw_input('Enter a number: ')
  if number == 'done' : break;
  try:
     numlist.append(float(number))
  except:
     print "Error, please enter a number, or 'done' to finish"
if len(numlist) == 0:
    # Preventing ValueError when list is empty
    print 'No minimum and maximum values available for an empty list.'
else:
   print 'Maximum =', max(numlist)
   print 'Minimum =', min(numlist)