1.1 Retrieve all lines from alice.txt that do not contain "the ". 

Note: if you express "not" by using 
	not keyword.search (line)
then the line with 
        print result.group(), ":", line,
will produce an error message. (Because there is no result, therefore
Python gets confused when you try to print it.) Therefore for this
exercise you must use the first example that was given on the webpage.
All other exercises can be done using the second example.

#!/usr/bin/env python
import re

# open a file
file = open("alice.txt","r")
text = file.readlines()
file.close()

# searching the file content line by line:
keyword = re.compile(r"the ")

for line in text:
    if not keyword.search (line):
       print line,


----

Retrieve all lines that contain "the" with lower or upper case letters.

#!/usr/bin/env python
import re

# open a file
file = open("alice.txt","r")
text = file.readlines()
file.close()

# searching the file content line by line:
keyword = re.compile(r"the ", re.I)

for line in text:
    result = keyword.search (line)
    if result:
       print result.group(), ":", line,

-----

2.1 Retrieve lines that have two consecutive o's.

#!/usr/bin/env python
import re

# open a file
file = open("alice.txt","r")
text = file.readlines()
file.close()

# searching the file content line by line:
keyword = re.compile(r"oo")

for line in text:
    result = keyword.search (line)
    if result:
       print result.group(), ":", line,

---

2.2 Retrieve lines that contain a three letter string consisting of "s", 
then any character, then "e", such as "she". 

keyword = re.compile(r"s.e")

---

2.3 Retrieve lines with a three letter word that starts with s and ends 
with e.

keyword = re.compile(r"\bs\we\b")

---

2.4 Retrieve lines that contain a word of any length that starts with s 
and ends with e. Modify this so that the word has at least four characters. 

Any length: 
keyword = re.compile(r"\bs\w*e\b")

At least four characters:
keyword = re.compile(r"\bs\w\w+e\b")

---

2.5 Retrieve lines that start with a. Retrieve lines that start with a and 
end with n.

Start with a:
keyword = re.compile(r"^a")

Start with a and end with n:
keyword = re.compile(r"^a.*n$")

---

2.6 Retrieve blank lines. Think of at least two ways of doing this.

keyword = re.compile(r"^$")

The second method uses "not" and thus cannot use the result.group()
statement:

# searching the file content line by line:
keyword = re.compile(r".")
for line in text:
     if not keyword.search(line):
         print line,

---

2.7 Retrieve lines that do not contain the blank space character. 

# searching the file content line by line:
keyword = re.compile(r" ")
for line in text:
     if not keyword.search(line):
         print line,

---

2.8 Retrieve lines that contain more than one blank space character. 

keyword = re.compile(r" .* ")

---

3 Add a few lines with numbers etc. to the end of the alice.txt file so 
that you can search for the following regular expressions: 

3.1 an odd digit followed by an even digit (eg. 12 or 74) 

keyword = re.compile(r"[13579][02468]")

---

3.2 a letter followed by a non-letter followed by a number 

keyword = re.compile(r"[A-Za-z][^A-Za-z]\d")

---

3.3 a word that starts with an upper case letter 

keyword = re.compile(r"\b[A-Z]\w*\b")

---

3.4 the word "yes" in any combination of upper and lower cases letters 

keyword = re.compile(r"\byes\b", re.I)

or 

keyword = re.compile(r"\b[Yy][Ee][Ss]\b")

---

3.5 one or more times the word "the" 

keyword = re.compile(r"(the )+")

---

3.6 a date in the form of one or two digits, a dot, one or two digits, a 
dot, two digits 

keyword = re.compile(r"\d\d?\.\d\d?\.\d\d")

---

3.7 a punctuation mark 

keyword = re.compile(r"[\.,\?\!:;]")

---

4.1 Write a script that asks users for their name, address and phone 
number. Test each input for accuracy, for example, there should be no 
letters in a phone number. A phone number should have a certain length. 
An address should have a certain format, etc. Ask the user to repeat the 
input in case your script identfies it as incorrect. 

#!/usr/bin/env python
import re

# the forbidden characters for names are:
# characters that are not letters, spaces or .
name_check = re.compile(r"[^A-Za-z\s\.]")

name = raw_input ("Please, enter your name: ")
while name_check.search(name):
    print "Please enter your name correctly!"
    name = raw_input ("Please, enter your name: ")

# the forbidden characters for addresses are:
# characters that are not word characters, spaces, "," or "."
address_check = re.compile(r"[^\w\s\.,]")

address = raw_input ("Please, enter your address: ")
while address_check.search(address):
    print "Please enter your address correctly!"
    address = raw_input ("Please, enter your address: ")

# the forbidden characters for phone numbers are:
# characters that are not numbers, parentheses, spaces or hyphen
phone_check = re.compile(r"[^0-9\s\-\(\)]")

phone = raw_input ("Please, enter your phone: ")
while phone_check.search(phone):
    print "Please enter your phone correctly!"
    phone = raw_input ("Please, enter your phone: ")