This presentation contains a quick tour in Python world. First by By comparing Java code, and the equivalent Python side by side, Second by listing some cool features in Python, finally by listing downs and ups of Python in usage; when to use python and when not.

1. Introduction to Python
A side-by-side comparison with Java
Tamer Mohammed Abdul-Radi
Backend Software Engineer at Cloud9ers ltd
tamer_radi
tamerradi

2. Python
Developed by Guido van Rossum during the
1989 Christmas holidays
Open source
Very readable
Programmer friendly

3. Python Versions
Python 2.7 Python 3.1
● Still widely used ● Present and Future
● Have an extended of the language
support ● Not backward
● Django, Twisted, compatible
and PIL supports ● Limited library
Python 2.x only support
● Comparison was made on 31 May 2012, things may change later
● There are two tools "2to3" and "3to2"' to convert scripts between versions

4. Python Tour
Compared to Java

5. Hello World
Java Python 2.7
public class Main { print "Hello World"
public static void main(String[] args) {
System.out.println("Hello World");
}
}
Python 3.x
print("Hello World")

6. Lists
Java Python
import java.util.Vector x = ['a', 'b', 'c', 'd']
public class Main { for item in x:
public static void main(String[] args) { print item
Vector x = new Vector();
x.addElement("a")
x.addElement("b")
x.addElement("c")
x.addElement("d")
for (int i = 0 ; i < x.length; i++) {
System.out.println(x.elementAt(i));
}
}
}

7. Lists vs Arrays
Java Python
Array Array
int[] a = {1, 2, 3}; import array
System.out.println(a[0]) a = array.array('i',
a[0] = 55 [1,2,3])
print a[0]
List
a[0] = 55
List<Integer> a = new
ArrayList<Integer>(); List
a.add(new Integer(1)) a = [1,2,3]
System.out.println(a.get(0)) print a[0]
a[0] = 55

8. Hashtables
Java Python
import java.util.Hashtable x = {}
public class Main { x['a'] = 1
public static void main(String[] args) { print x['a']
Hashtable x = new Hashtable();
x.put("a", new Integer(1))
System.out.println(x.get("a"));
OR
}
x = {'a' : 1}
}
print x['a']

9. IO
Java Python
public class Main { f = open('file.txt', 'w')
public static void main(String[] args) { f.write('Hello World')
try { f.close()
File f = new File('file.txt');
PrintWriter ps = new PrintWriter(
new OutputStreamWriter(
new File OutputStream(f)));
OR
ps.print("Hello World")
}
catch (IOException e) {
with open('file.txt, 'w') as f:
e.printStackTrace();
f.write('Hello World')
}
}
}

10. Classes
Java Python
public class Point { class Point():
public int x; def __init__(self, x, y) {
public int y; self.x = x
public MyClass(int x, int y) { self.y = y
this.x = x }
this.y = y p = Point(1, 2)
}
public static void main(String[] args) {
p = new Point(1, 2)
}
}

11. Interesting Features
in Python Programming Language

12. Introspection
The ability to examine something to determine
● what it is
● what it knows
● what it is capable of doing
Introspection gives programmers a great deal
of flexibility and control.
Source: http://www.ibm.com/developerworks/library/l-pyint/index.html

13. Syntactic Sugar for very high level
data structures
Lists Tuples
l = ['a', 'b', 'c', 'd'] t = ('a', 'b', 'c', 'd')
print l[0] print t[0]
l[0] = 'z'
Strings
Hashtables s = 'abcd'
d = {0:'a', 100:'b', 5:'c'} print s[0]
print d[0]
d['strings_too'] = 'z' Sets
s = {0, 1, 2, 3}

14. Enhanced For
for item in l:
print item
for char in s: There is no special type for
chars; A char in python is
print char
string with length equals one
for item in t:
print item

15. Enhanced For
for key in d:
print key
for value in d.values():
print value
for key, value in d.items():
print key, value

16. Positional & Keyword Arguments
def my_function(a, b, c, d):
print a, b, c, d
my_function(1, 2, 3, 4)
my_function(a=1, b=2, c=3, d=4)
my_function(1, b=2, c=3, d=4)
my_function(1, 2, c=3, d=4)
my_function(1, 2, d=4, c=3)

17. OOP
● Everything is an object
● No Primitives, integers are objects
● Functions are objects,
○ you can send a function as parameter to another
function
○ you can have a list of functions
● Classes are objects!

18. Things you can kiss goodbye
● Curly Braces to define Blocks
● Semicolons (optional)
● Switch case
● Classic For Loops
● Interfaces
● Checked Exceptions

19. Things you won't miss in Python
● Simplicity
● Readability
● True OOP
● Fun!

20. Things Python sucks at
● Lots of mathematical computations
You can write the computation code in C ,or
C++ and call it from Python!
● Using multithreading with mutli-cores or CPUs
You can multiprocessing rather than multi-
threading

21. What is Python good for?
● String processing (regular expressions, Unicode,
calculating differences between files)
● Internet protocols (HTTP, FTP, SMTP, XML-RPC, POP,
IMAP, CGI programming)
● Software engineering (unit testing, logging, profiling,
parsing Python code)
● Operating system interfaces (system calls, file systems,
TCP/IP sockets)