chapter 35 – python
DESCRIPTION
Chapter 35 – Python. Outline 35.1 Introduction 35.1.1First Python Program 35.1.2Python Keywords 35.2 Basic Data Types, Control Statements and Functions 35.3 Tuples, Lists and Dictionaries 35.4 String Processing and Regular Expressions 35.5 Exception Handling - PowerPoint PPT PresentationTRANSCRIPT
2004 Prentice Hall, Inc. All rights reserved.
Chapter 35 – Python
Outline35.1 Introduction
35.1.1 First Python Program35.1.2 Python Keywords
35.2 Basic Data Types, Control Statements and Functions35.3 Tuples, Lists and Dictionaries35.4 String Processing and Regular Expressions35.5 Exception Handling35.6 Introduction to CGI Programming35.7 Form Processing and Business Logic35.8 Cookies35.9 Database Application Programming Interface (DB-API)
35.9.1 Setup35.9.2 Simple DB-API Program
35.10 Operator Precedence Chart35.11 Web Resources
2004 Prentice Hall, Inc. All rights reserved.
Objectives
• In this lesson, you will learn:– To understand basic Python data types.
– To understand string processing and regular expressions in Python.
– To use exception handling.
– To perform basic CGI tasks in Python.
– To construct programs that interact with MySQL databases using the Python Database Application Programming Interface (DB-API).
2004 Prentice Hall, Inc. All rights reserved.
35.1 Introduction
• Python– Interpreted
– Cross-platform
– Object-oriented
– Large-scale Internet search engines
– Small administration scripts
– GUI applications
– CGI scripts
– Freely distributed
2004 Prentice Hall, Inc. All rights reserved.
35.1.1 First Python Program
• Python– Can be executed on a program stored in a file
– Can run in interactive mode• Users enter lines of code one at a time
• Enables programmers to test small blocks of code quickly
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_01.py(1 of 1)
1 # Fig. 35.1: fig35_01.py
2 # A first program in Python
3
4 print "Welcome to Python!"
Welcome to Python!
2004 Prentice Hall, Inc. All rights reserved.
35.1.1 First Python Program
Python 2.1 (#15, Apr 16 2001, 18:25:49) [MSC 32 bit (Intel)] on win32 Type "copyright", "credits" or "license" for more information. >>> print "Welcome to Python!" Welcome to Python! >>> ^Z
Fig. 35.2 Python in interactive mode.
2004 Prentice Hall, Inc. All rights reserved.
35.1.2 Python Keywords
• Python is case-sensitive• Keywords can be obtained from keyword module
2004 Prentice Hall, Inc. All rights reserved.
35.1.2 Python Keywords
Python keywords
and continue else for import not raise assert def except from in or return break del exec global is pass try class elif finally if lambda print while Fig. 35.3 Python keywords.
Python 2.1 (#15, Apr 16 2001, 18:25:49) [MSC 32 bit (Intel)] on win32 Type "copyright", "credits" or "license" for more information. >>> import keyword >>> print keyword.kwlist ['and', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'exec', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or', 'pass', 'print', 'raise', 'return', 'try', 'while'] >>>
Fig. 35.4 Printing Python keywords in interactive mode.
2004 Prentice Hall, Inc. All rights reserved.
35.2 Basic Data Types, Control Statements and Functions
• Introduces basic data types, control statements, and functions– while loop– if statement
– Modulo operator ( % )– return keyword– if…elif…else statement
– Line-continuation character ( \ )
– Escape sequences
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_05.py(1 of 2)
1 # Fig. 35.5: fig35_05.py
2 # Program to illustrate basic data types, control structures and
3 # functions.
4
5 def greatestCommonDivisor( x, y ):
6 gcd = min( x, y )
7
8 while gcd >= 1:
9
10 if ( x % gcd ) == ( y % gcd ) == 0:
11 return gcd
12 else:
13 gcd -= 1
14
15 def determineColor( color ):
16
17 if color == "green":
18 print "You entered green!"
19 elif color == "purple":
20 print "You entered purple!"
21 else:
22 print "You did not enter green or purple."
23
24 number1 = int( raw_input( "Enter a positive integer: " ) )
25 number2 = int( raw_input( "Enter a positive integer: " ) )
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_05.py(2 of 2)
26
27 print "The greatest common divisor is", \
28 greatestCommonDivisor( number1, number2 )
29
30 for entry in range( 5 ):
31 colorChoice = raw_input( "\nEnter your favorite color: " )
32 determineColor( colorChoice )
Enter a positive integer: 2 Enter a positive integer: 30 The greatest common divisor is 2 Enter your favorite color: yellow You did not enter green or purple. Enter your favorite color: green You entered green! Enter your favorite color: black You did not enter green or purple. Enter your favorite color: purple You entered purple! Enter your favorite color: red You did not enter green or purple.
2004 Prentice Hall, Inc. All rights reserved.
35.2 Basic Data Types, Control Statements and Functions
Escape sequence
Meaning
\n Newline (line feed). \r Carriage return. \t Tab. \' Single quote. \" Double quote. \b Backspace. \\ Backslash. Fig. 35.6 Escape sequences.
2004 Prentice Hall, Inc. All rights reserved.
35.3 Tuples, Lists and Dictionaries
• list– A sequence of related data
• Tuple– A list whose elements may not be modified
– Immutable
– Singleton• One-element tuple
• Dictionary– A list of values that are accessed through their associated
keys
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_07.py(1 of 3)
1 # Fig. 35.7: fig35_07.py
2 # A program that illustrates tuples, lists and dictionaries.
3
4 # tuples
5 aTuple = ( 1, "a", 3.0 ) # create tuple
6 firstItem = aTuple[ 0 ] # first tuple item
7 secondItem = aTuple[ 1 ] # second tuple item
8 thirdItem = aTuple[ 2 ] # third tuple item
9
10 print "The first item in the tuple is", firstItem
11 print "The second item in the tuple is", secondItem
12 print "The third item in the tuple is", thirdItem
13 print
14
15 firstItem, secondItem, thirdItem = aTuple
16 print "The first item in the tuple is", firstItem
17 print "The second item in the tuple is", secondItem
18 print "The third item in the tuple is", thirdItem
19 print
20
21 aTuple += ( 4, )
22 print "Used the += statement on the tuple"
23 print
24
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_07.py(2 of 3)
25 # print the tuple
26 print "The raw tuple data is:", aTuple
27 print "The items in the tuple are:"
28
29 for item in aTuple: # print each item
30 print item,
31
32 print # end previous line
33 print # blank line
34
35 # lists
36 aList = [ 1, 2, 3 ] # create list
37 aList[ 0 ] = 0 # change first element of list
38 aList.append( 5 ) # add item to end of list
39
40 print "The raw list data is:", aList # print list data
41 print
42
43 aList += [ 4 ] # add an item to the end of the list
44 print "Added an item to the list using the += statement"
45 print
46
47 # print each item in the list
48 print "The items in the list are:"
49
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_07.py(3 of 3)
50 for item in aList:
51 print item,
52
53 print # end previous line
54 print # blank line
55
56 # dictionaries
57 aDictionary = { 1 : "January", 2 : "February", 3 : "March",
58 4 : "April", 5 : "May", 6 : "June", 7 : "July",
59 8 : "August", 9 : "September", 10 : "October",
60 11 : "November" }
61 aDictionary[ 12 ] = "December" # add item to dictionary
62
63 print "The raw dictionary data is:", aDictionary
64 print "\nThe entries in the dictionary are:"
65
66 for item in aDictionary.keys():
67 print "aDictionary[ ", item, " ] = ", aDictionary[ item ]
2004 Prentice Hall, Inc. All rights reserved.
The first item in the tuple is 1 The second item in the tuple is a The third item in the tuple is 3.0 The first item in the tuple is 1 The second item in the tuple is a The third item in the tuple is 3.0 Used the += statement on the tuple The raw tuple data is: (1, 'a', 3.0, 4) The items in the tuple are: 1 a 3.0 4 The raw list data is: [0, 2, 3, 5] Added an item to the list using the += statement The items in the list are: 0 2 3 5 4 The raw dictionary data is: {12: 'December', 11: 'November', 10: 'October', 9: 'September', 8: 'August', 7: 'July', 6: 'June', 5: 'May', 4: 'April', 3: 'March', 2: 'February', 1: 'January'} The entries in the dictionary are: aDictionary[ 12 ] = December aDictionary[ 11 ] = November aDictionary[ 10 ] = October aDictionary[ 9 ] = September aDictionary[ 8 ] = August aDictionary[ 7 ] = July aDictionary[ 6 ] = June aDictionary[ 5 ] = May aDictionary[ 4 ] = April aDictionary[ 3 ] = March aDictionary[ 2 ] = February aDictionary[ 1 ] = January
2004 Prentice Hall, Inc. All rights reserved.
35.3 Tuples, Lists and Dictionaries
Method Purpose append( item ) Inserts item at the end of the list. count( item ) Returns the number of occurrences of item in the list. extend( newList ) Inserts newList at the end of the list. index( item ) Returns the index of the first occurrence of item in the list.
If the element is not in the list, a ValueError exception occurs. [Note: We discuss exceptions in Section 35.5]
insert( index, item )
Inserts item at position index.
pop( [index] ) Removes and returns the last element in the list. If parameter index is specified, removes and returns the element at position index.
remove( item ) Removes the first occurrence of item from the list. If item is not in the list, a ValueError exception occurs.
reverse() Reverses the items in the list. sort( [function] ) Sorts the items in the list. Optional parameter function is a
comparison function that may be user defined. Fig. 35.8 Python list methods.
2004 Prentice Hall, Inc. All rights reserved.
35.3 Tuples, Lists and Dictionaries
Method Description clear() Deletes all items from the dictionary. copy() Creates a copy of the dictionary. get( key [, falseValue] ) Returns the value associated with key. If key is not
in the dictionary and if falseValue is specified, returns the specified value.
has_key( key ) Returns 1 if key is in the dictionary; returns 0 if key is not in the dictionary.
items() Returns a list of tuples that are key-value pairs. keys() Returns a list of keys in the dictionary. setdefault( key [, falseValue] )
Behaves similarly to method get. If key is not in the dictionary and falseValue is specified, inserts the key and the specified value into the dictionary.
update( otherDictionary ) Adds all the key-value pairs from otherDictionary to the current dictionary.
values() Returns a list of values in the dictionary. Fig. 35.9 Dictionary methods.
2004 Prentice Hall, Inc. All rights reserved.
35.4 String Processing and Regular Expressions
• Regular expression– Used to search through strings, text files, databases, and so
on
• Regular-expression string– Defines a pattern with which text data can be compared
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_10.py(1 of 2)
1 # Fig. 35.10: fig35_10.py
2 # Program to illustrate use of strings
3
4 # simple string assignments
5 string1 = "This is a string."
6 print string1
7
8 string2 = "This is a second string."
9 print string2
10
11 # string concatenation
12 string3 = string1 + " " + string2
13 print string3
14
15 # using operators
16 string4 = '*'
17 print "String with an asterisk: " + string4
18 string4 *= 10
19 print "String with 10 asterisks: " + string4
20
21 # using quotes
22 print "This is a string with \"double quotes.\""
23 print 'This is another string with "double quotes."'
24 print 'This is a string with \'single quotes.\''
25 print "This is another string with 'single quotes.'"
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_10.py(2 of 2)
26 print """This string has "double quotes" and 'single quotes.'"""
27
28 # string formatting
29 name = raw_input( "Enter your name: " )
30 age = raw_input( "Enter your age: " )
31 print "Hello, %s, you are %s years old." % ( name, age )
This is a string. This is a second string. This is a string. This is a second string. String with an asterisk: * String with 10 asterisks: ********** This is a string with "double quotes." This is another string with "double quotes." This is a string with 'single quotes.' This is another string with 'single quotes.' This string has "double quotes" and 'single quotes.' Enter your name: Brian Enter your age: 33 Hello, Brian, you are 33 years old.
2004 Prentice Hall, Inc. All rights reserved.
35.4 String Processing and Regular Expressions
Symbol Meaning c Single character (i.e., a string of length 1). s String. d Signed decimal integer. u Unsigned decimal integer. o Unsigned octal integer. x Unsigned hexadecimal integer (using format abcdef). X Unsigned hexadecimal integer (using format ABCDEF). f Floating-point number. e, E Floating-point number (using scientific notation). g, G Floating-point number (using least-significant digits). Fig. 35.11 String-format characters.
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_12.py(1 of 2)
1 # Fig. 35.12: fig35_12.py
2 # Program searches a string using the regular expression module.
3
4 import re
5
6 searchString = "Testing pattern matches"
7
8 expression1 = re.compile( r"Test" )
9 expression2 = re.compile( r"^Test" )
10 expression3 = re.compile( r"Test$" )
11 expression4 = re.compile( r"\b\w*es\b" )
12 expression5 = re.compile( r"t[aeiou]", re.I )
13
14 if expression1.search( searchString ):
15 print '"Test" was found.'
16
17 if expression2.match( searchString ):
18 print '"Test" was found at the beginning of the line.'
19
20 if expression3.match( searchString ):
21 print '"Test" was found at the end of the line.'
22
23 result = expression4.findall( searchString )
24
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_12.py(2 of 2)
25 if result:
26 print 'There are %d words(s) ending in "es":' % \
27 ( len( result ) ),
28
29 for item in result:
30 print " " + item,
31
32 print
33 result = expression5.findall( searchString )
34
35 if result:
36 print 'The letter t, followed by a vowel, occurs %d times:' % \
37 ( len( result ) ),
38
39 for item in result:
40 print " " + item,
41
42 print
2004 Prentice Hall, Inc. All rights reserved.
35.4 String Processing and Regular Expressions
Character Matches ^ Beginning of string. $ End of string. . Any character, except a newline. * Zero or more occurrences of the pattern. + One or more occurrences of the preceding pattern. ? Zero or one occurrence of the preceding pattern. {m, n} Between m and n occurrences of the preceding pattern. \b Word boundary (i.e., the beginning or end of a word). \B Nonword boundary. \d Digit ([0–9]). \D Nondigit. \w Any alpha-numeric character. [...] Any character defined by the set. [^...] Any character not defined by the set. Fig. 35.13 re module’s regular-expression characters.
2004 Prentice Hall, Inc. All rights reserved.
35.5 Exception Handling
• Enables programs and programmers to identify an error when it occurs and take appropriate action
• try…except blocks
2004 Prentice Hall, Inc. All rights reserved.
35.5 Exception Handling
Python 2.1 (#15, Apr 16 2001, 18:25:49) [MSC 32 bit (Intel)] on win32 Type "copyright", "credits" or "license" for more information. >>> 1 / 0 Traceback (most recent call last): File "<stdin>", line 1, in ? ZeroDivisionError: integer division or modulo by zero >>>
Fig. 35.14 Interactive session illustrating a ZeroDivisionError exception.
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_15.py(1 of 1)
1 # Fig. 35.15: fig35_15.py
2 # A simple program that illustrates exceptions.
3
4 def getFloat():
5 return float( raw_input( "Enter a number: " ) )
6
7 number1 = number2 = None
8
9 while number1 == None:
10 try:
11 number1 = getFloat()
12 except ValueError:
13 print "Value entered was not a number"
14
15 while number2 == None:
16 try:
17 number2 = getFloat()
18 except ValueError:
19 print "Value entered was not a number"
20
21 try:
22 result = number1 / number2
23 except ZeroDivisionError:
24 print "Cannot divide by zero!"
25 else:
26 print "The result of division is: %f" % result
2004 Prentice Hall, Inc. All rights reserved.
35.6 Introduction to CGI Programming
• Use Python on the Web– cgi
• For access to XHTML forms• Directive (pound-bang or Shebang)
– Provides server with location of Python executable• cgi module
– Provides functionalities for writing CGI scripts• environ data member
– Holds all environment variables
– Cookie• To read and write cookies
– smtplib• To manipulate SMTP messages
– urllib• To manipulate Web data
– ftplib• To perform client-side FTP tasks
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_16.py(1 of 2)
1 #!c:\Python\python.exe
2 # Fig 35.16: fig35_16.py
3 # Program to display CGI environment variables
4
5 import os
6 import cgi
7
8 print "Content-type: text/html"
9 print
10
11 print """<!DOCTYPE html PUBLIC
12 "-//W3C//DTD XHTML 1.0 Transitional//EN"
13 "DTD/xhtml1-transitional.dtd">"""
14
15 print """
16 <html xmlns = "http://www.w3.org/1999/xhtml" xml:lang="en"
17 lang="en">
18 <head><title>Environment Variables</title></head>
19 <body><table style = "border: 0">"""
20
21 rowNumber = 0
22
23 for item in os.environ.keys():
24 rowNumber += 1
25
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_16.py(2 of 2)
26 if rowNumber % 2 == 0:
27 backgroundColor = "white"
28 else:
29 backgroundColor = "lightgrey"
30
31 print """<tr style = "background-color: %s">
32 <td>%s</td><td>%s</td></tr>""" \
33 % ( backgroundColor, item,
34 cgi.escape( os.environ[ item ] ) )
35
36 print """</table></body></html>"""
2004 Prentice Hall, Inc. All rights reserved.
35.7 Form Processing and Business Logic
• XHTML forms– Allow users to enter data to be sent to a Web server for
processing
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_17.html(1 of 3)
1 <!DOCTYPE html PUBLIC
2 "-//W3C//DTD XHTML 1.0 Transitional//EN"
3 "DTD/xhtml1-transitional.dtd">
4 <!-- Fig. 35.17: fig35_17.html -->
5
6 <html xmlns = "http://www.w3.org/1999/xhtml" xml:lang="en"
7 lang="en">
8 <head>
9 <title>Sample FORM to take user input in HTML</title>
10 </head>
11
12 <body style = "font-family: Arial, sans-serif; font-size: 11pt">
13
14 <div style = "font-size: 15pt; font-weight: bold">
15 This is a sample registration form.
16 </div>
17 Please fill in all fields and click Register.
18
19 <form method = "post" action = "/cgi-bin/fig35_18.py">
20 <img src = "images/user.gif" alt = "user" /><br />
21 <div style = "color: blue">
22 Please fill out the fields below.<br />
23 </div>
24
25 <img src = "images/fname.gif" alt = "firstname" />
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_17.html(2 of 3)
26 <input type = "text" name = "firstname" /><br />
27 <img src = "images/lname.gif" alt = "lastname" />
28 <input type = "text" name = "lastname" /><br />
29 <img src = "images/email.gif" alt = "email" />
30 <input type = "text" name = "email" /><br />
31 <img src = "images/phone.gif" alt = "phone" />
32 <input type = "text" name = "phone" /><br />
33
34 <div style = "font-size: 8pt">
35 Must be in the form (555)555-5555<br/><br/>
36 </div>
37
38 <img src = "images/downloads.gif" alt = "downloads" /><br />
39 <div style = "color: blue">
40 Which book would you like information about?<br />
41 </div>
42
43 <select name = "book">
44 <option>XML How to Program</option>
45 <option>Python How to Program</option>
46 <option>E-business and E-commerce How to Program</option>
47 <option>Internet and WWW How to Program 3e</option>
48 <option>C++ How to Program 4e</option>
49 <option>Java How to Program 5e</option>
50 <option>Visual Basic How to Program</option>
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_17.html(3 of 3)
51 </select>
52 <br /><br />
53
54 <img src = "images/os.gif" alt = "os" /><br />
55 <div style = "color: blue">
56 Which operating system are you
57 currently using?<br />
58 </div>
59
60 <input type = "radio" name = "os" value = "Windows XP"
61 checked = "checked" />
62 Windows XP
63 <input type = "radio" name = "os" value = "Windows 2000" />
64 Windows 2000
65 <input type = "radio" name = "os" value = "Windows 95_98" />
66 Windows 95/98/ME<br />
67 <input type = "radio" name = "os" value = "Linux" />
68 Linux
69 <input type = "radio" name = "os" value = "Other" />
70 Other<br />
71 <input type = "submit" value = "Register" />
72
73 </form>
74 </body>
75 </html>
2004 Prentice Hall, Inc. All rights reserved.
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_18.py(1 of 4)
1 #!c:\Python\python.exe
2 # Fig. 35.18: fig35_18.py
3 # Program to read information sent to the server from the
4 # form in the form.html document.
5
6 import cgi
7 import re
8
9 # the regular expression for matching most US phone numbers
10 telephoneExpression = \
11 re.compile( r'^\(\d{3}\)\d{3}-\d{4}$' )
12
13 def printContent():
14 print "Content-type: text/html"
15 print
16 print """
17 <html xmlns = "http://www.w3.org/1999/xhtml" xml:lang="en"
18 lang="en">
19 <head><title>Registration results</title></head>
20 <body>"""
21
22 def printReply():
23 print """
24 Hi <span style = "color: blue; font-weight: bold">
25 %(firstName)s</span>.
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_18.py(2 of 4)
26 Thank you for completing the survey.<br />
27 You have been added to the <span style = "color: blue;
28 font-weight: bold">%(book)s </span> mailing list.<br /><br />
29
30 <span style = "font-weight: bold">
31 The following information has been saved in our database:
32 </span><br />
33
34 <table style = "border: 0; border-width: 0;
35 border-spacing: 10">
36 <tr><td style = "background-color: yellow">Name </td>
37 <td style = "background-color: yellow">Email</td>
38 <td style = "background-color: yellow">Phone</td>
39 <td style = "background-color: yellow">OS</td></tr>
40
41 <tr><td>%(firstName)s %(lastName)s</td><td>%(email)s</td>
42 <td>%(phone)s</td><td>%(os)s</td></tr>
43 </table>
44
45 <br /><br /><br />
46
47 <div style = "text-align: center; font-size: 8pt">
48 This is only a sample form.
49 You have not been added to a mailing list.
50 </div></center>
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_18.py(3 of 4)
51 """ % personInfo
52
53 def printPhoneError():
54
55 print """<span style = "color: red; font-size 15pt">
56 INVALID PHONE NUMBER</span><br />
57 A valid phone number must be in the form
58 <span style = "font-weight: bold">(555)555-5555</span>
59 <span style = "color: blue"> Click the Back button,
60 enter a valid phone number and resubmit.</span><br /><br />
61 Thank You."""
62
63 def printFormError():
64
65 print """<span style = "color: red; font-size 15pt">
66 FORM ERROR</span><br />
67 You have not filled in all fields.
68 <span style = "color: blue"> Click the Back button,
69 fill out the form and resubmit.</span><br /><br />
70 Thank You."""
71
72 printContent()
73
74 form = cgi.FieldStorage()
75
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_18.py(4 of 4)
76 try:
77 personInfo = { 'firstName' : form[ "firstname" ].value,
78 'lastName' : form[ "lastname" ].value,
79 'email' : form[ "email" ].value,
80 'phone' : form[ "phone" ].value,
81 'book' : form[ "book" ].value,
82 'os' : form[ "os" ].value }
83 except KeyError:
84 printFormError()
85
86 if telephoneExpression.match( personInfo[ 'phone' ] ):
87 printReply()
88 else:
89 printPhoneError()
2004 Prentice Hall, Inc. All rights reserved.
35.8 Cookies
• Small text files– State information
• Username
• Password
• Specific information helpful when user returns
• Etc.
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_19.html(1 of 2)
1 <!DOCTYPE html PUBLIC
2 "-//W3C//DTD XHTML 1.0 Transitional//EN"
3 "DTD/xhtml1-transitional.dtd">
4 <!-- Fig. 35.19: fig35_19.html -->
5
6 <html xmlns = "http://www.w3.org/1999/xhtml" xml:lang = "en"
7 lang = "en">
8 <head>
9 <title>Writing a cookie to the client computer</title>
10 </head>
11
12 <body style = "background-image: images/back.gif;
13 font-family: Arial,sans-serif; font-size: 11pt" >
14
15 <span style = "font-size: 15pt; font-weight: bold">
16 Click Write Cookie to save your cookie data.
17 </span><br />
18
19 <form method = "post" action = "/cgi-bin/fig35_20.py">
20 <span style = "font-weight: bold">Name:</span><br />
21 <input type = "text" name = "name" /><br />
22 <span style = "font-weight: bold">Height:</span><br />
23 <input type = "text" name = "height" /><br />
24 <span style = "font-weight: bold">Favorite Color</span><br />
25 <input type = "text" name = "color" /><br />
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_19.html(2 of 2)
26 <input type = "submit" value = "Write Cookie" />
27 </form>
28
29 </body>
30 </html>
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_20.py(1 of 3)
1 #!C:\Python\python.exe
2 # Fig. 35.20: fig35_20.py
3 # Writing a cookie to a client's machine
4
5 import cgi
6 import Cookie
7 import time
8
9 def printContent():
10 print "Content-type: text/html"
11 print
12 print """
13 <html xmlns = "http://www.w3.org/1999/xhtml" xml:lang="en"
14 lang="en">
15 <head><title>Cookie values</title></head>"""
16
17 form = cgi.FieldStorage() # get form information
18
19 try: # extract form values
20 name = form[ "name" ].value
21 height = form[ "height" ].value
22 color = form[ "color" ].value
23 except KeyError:
24 printContent()
25 print """<body><h3>You have not filled in all fields.
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_20.py(2 of 3)
26 <span style = "color: blue"> Click the Back button,
27 fill out the form and resubmit.<br /><br />
28 Thank You. </span></h3>"""
29 else:
30
31 # construct cookie expiration date and path
32 expirationFormat = "%A, %d-%b-%y %X %Z"
33 expirationTime = time.localtime( time.time() + 300 )
34 expirationDate = time.strftime( expirationFormat,
35 expirationTime )
36 path = "/"
37
38 # construct cookie contents
39 cookie = Cookie.SimpleCookie()
40
41 cookie[ "Name" ] = name
42 cookie[ "Name" ][ "expires" ] = expirationDate
43 cookie[ "Name" ][ "path" ] = path
44
45 cookie[ "Height" ] = height
46 cookie[ "Height" ][ "expires" ] = expirationDate
47 cookie[ "Height" ][ "path" ] = path
48
49 cookie[ "Color" ] = color
50 cookie[ "Color" ][ "expires" ] = expirationDate
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_20.py(3 of 3)
51 cookie[ "Color" ][ "path" ] = path
52
53 # print cookie to user and page to browser
54 print cookie
55
56 printContent()
57 print """<body style = "background-image: /images/back.gif;
58 font-family: Arial,sans-serif; font-size: 11pt">
59 The cookie has been set with the following data: <br /><br />
60
61 <span style = "color: blue">Name:</span> %s<br />
62 <span style = "color: blue">Height:</span> %s<br />
63 <span style = "color: blue">Favorite Color:</span>
64 <span style = "color: %s"> %s</span><br />""" \
65 % ( name, height, color, color )
66
67 print """<br /><a href= "fig35_21.py">
68 Read cookie values</a>"""
69
70 print """</body></html>"""
2004 Prentice Hall, Inc. All rights reserved.
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_21.py(1 of 2)
1 #!C:\Python\python.exe
2 # Fig. 35.21: fig35_21.py
3 # Program that retrieves and displays client-side cookie values
4
5 import Cookie
6 import os
7
8 print "Content-type: text/html"
9 print
10 print """
11 <html xmlns = "http://www.w3.org/1999/xhtml" xml:lang="en"
12 lang="en">
13 <head><title>Cookie values</title></head>
14 <body style =
15 font-family: Arial, sans-serif; font-size: 11pt">"""
16
17 try:
18 cookie = Cookie.SimpleCookie()
19 cookie.load( os.environ[ "HTTP_COOKIE" ] )
20 except KeyError:
21 print """<span style = "font-weight: bold">Error reading cookies
22 </span>"""
23 else:
24 print """<span style = "font-weight: bold">
25 The following data is saved in a cookie on your computer.
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_21.py(2 of 2)
26 </span><br /><br />"""
27
28 print """<table style = "border-width: 5; border-spacing: 0;
29 padding: 10">"""
30
31 for item in cookie.keys():
32 print """<tr>
33 <td style = "background-color: lavender">%s</td>
34 <td style = "background-color: white">%s</td>
35 </tr>""" % ( item, cookie[ item ].value )
36
37 print """</table>"""
38
39 print """</body></html>"""
2004 Prentice Hall, Inc. All rights reserved.
35.9 Database Application Programming Interface (DB-API)
• Python Database Special Interest Group (SIG)– Formed to develop a specification for Python database
application programming interface (DB-API)
2004 Prentice Hall, Inc. All rights reserved.
35.9.1 Setup
• MySQL and the MySQLdb module must be installed
2004 Prentice Hall, Inc. All rights reserved.
35.9.2 Simple DB-API Program
• Lets user choose an author from XHTML drop-down list
• User clicks button to query database• Database query returns a list of all books by
author
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_22.py(1 of 2)
1 #!c:\Python\python.exe
2 # Fig. 35.22: fig35_22.py
3 # A program to illustrate Python's database connectivity.
4 import MySQLdb
5
6 print "Content-type: text/html"
7 print
8 print """
9 <html xmlns = "http://www.w3.org/1999/xhtml" xml:lang="en"
10 lang="en">
11 <head><title>Select Author</title></head>
12 <body style =
13 font-family: Arial, sans-serif; font-size: 11pt">"""
14
15 try:
16 connection = MySQLdb.connect( db = "books" )
17 except OperationalError:
18 print "Unable to connect to database: %s" % message
19 else:
20 cursor = connection.cursor()
21 cursor.execute( "SELECT * FROM Authors" )
22 authorList = cursor.fetchall()
23
24 cursor.close() # close cursor
25 connection.close() # close connection
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_22.py(2 of 2)
26
27 print """
28 <form method = "post" action = "/cgi-bin/fig35_23.py">
29 <select name = "authorID">"""
30
31 for author in authorList:
32 print """<option value = %d>%s, %s</option>""" \
33 % ( author[ 0 ], author[ 2 ], author[ 1 ] )
34
35 print """
36 </select>
37 <input type = "submit" value = "Execute Query" />
38 </ form>"""
39
40 print """</body></html>"""
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_23.py1 of 3
1 #!c:\Python\python.exe
2 # Fig. 35.23: fig35_23.py
3 # A program to illustrate Python's database connectivity.
4
5 import cgi
6 import MySQLdb
7 import sys
8
9 # get results from form
10 form = cgi.FieldStorage()
11
12 print "Content-type: text/html"
13 print
14 print """
15 <html xmlns = "http://www.w3.org/1999/xhtml" xml:lang="en"
16 lang="en">
17 <head><title>Query results</title></head>
18 <body style =
19 font-family: Arial, sans-serif; font-size: 11pt">"""
20
21 try:
22 authorID = form[ "authorID" ].value
23 except KeyError:
24 print """<span style = "color: red size = 15pt">
25 FORM ERROR</span><br />
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_23.py(2 of 3)
26 You did not select an author.<br />
27 <span style = "color: blue"> Click the Back button,
28 fill out the form and resubmit.<br /><br />
29 Thank You.</span></body></html>"""
30 sys.exit()
31
32 # connect to database and get cursor
33 try:
34 connection = MySQLdb.connect( db = 'books' )
35 except OperationalError:
36 print """<span style = "color: red size = 15pt">
37 DATABASE ERROR</span><br /> Unable to connect to database.
38 </body></html>"""
39 sys.exit()
40
41 queryString = """select Titles.* from Titles, AuthorISBN
42 where AuthorISBN.AuthorID=%s and
43 Titles.ISBN=AuthorISBN.ISBN""" % authorID
44
45 cursor = connection.cursor()
46 cursor.execute( queryString )
47
48 results = cursor.fetchall()
49
50 cursor.close() # close cursor
2004 Prentice Hall, Inc.All rights reserved.
OutlineOutline
fig35_23.py(3 of 3)
51 connection.close() # close connection
52
53 # display results
54 print """<table style = "border: groove 2 pt;
55 border-colapse: separate">
56 <tr>
57 <th>ISBN</th>
58 <th>Title</th>
59 <th>Edition</th>
60 <th>Year</th>
61 <th>Description</th>
62 <th>Publisher ID</th>
63 </tr>"""
64
65 for row in results:
66 print "<tr>"
67
68 for entry in row:
69 print '<td style = "border: solid 2pt">%s</td>' % entry
70
71 print "</tr>"
72
73 print """</table></body></html>"""
2004 Prentice Hall, Inc. All rights reserved.
2004 Prentice Hall, Inc. All rights reserved.
35.10 Operator Precedence Chart
Operator Type Associativity ' ' string conversion left to right
{ } dictionary creation left to right [ ] list creation left to right ( ) tuple creation or expression grouping left to right ( ) function call left to right [ : ] slicing left to right [ ] subscript access left to right . member access left to right ** exponentiation right to left ~ bitwise NOT left to right + -
unary plus unary minus
right to left
* / %
multiplication division modulus (remainder)
left to right
Fig. 35.24 Python operator precedence chart.
2004 Prentice Hall, Inc. All rights reserved.
35.10 Operator Precedence Chart
Operator Type Associativity + -
addition subtraction
left to right
<< >>
left shift right shift
left to right
& bitwise AND left to right ^ bitwise XOR left to right | bitwise OR left to right < <= > >= != ==
less than less than or equal greater than greater than or equal not equal equal
left to right
Fig. 35.24 Python operator precedence chart.
2004 Prentice Hall, Inc. All rights reserved.
35.10 Operator Precedence Chart
Operator Type Associativity is, is not identity left to right
in, not in membership tests left to right not boolean NOT left to right and boolean AND left to right or boolean OR left to right lambda lambda expressions (anonymous
functions) left to right
Fig. 35.24 Python operator precedence chart.
2004 Prentice Hall, Inc. All rights reserved.
35.11 Web Resources
• www.python.org• www.zope.com• www.zope.org• starship.python.net• www.python.org/download/download_mac.html• www.vex.net/parnassus• www.pythonware.com• starship.python.net/crew/davem/cgifaq/faqw.cgi• www.devshed.com/Server_Side/Python/CGI• starship.python.net/crew/aaron_watters/pws.html• www.python.org/doc/howto/regex/regex.html• www.python.org/windows/win32com• gadfly.sourceforge.net• aspn.activestate.com/ASPN/Python/Cookbook• www.python.org/windows/win32/odbc.html• starship.python.net/crew/bwilk/access.html• www.python.org/doc/Comparisons.html• www.vic.auug.org.au/auugvic/av_paper_python.html• www.networkcomputing.com/unixworld/tutorial/005/005.html