Who made it?

Over six years ago, in December 1989,
I was looking for a "hobby" programming project that would keep me occupied during the week around Christmas.
My office ... would be closed, but I had a home computer, and not much else on my hands.
I decided to write an interpreter for the new scripting language I had been thinking about lately: a descendant of ABC that would appeal to Unix/C hackers.
I chose Python as a working title for the project, being in a slightly irreverent mood
(and a big fan of Monty Python's Flying Circus).

Features of Python

Middle language

object-oriented programming

 
class Person:
    def __init__(self, name, height):
        self.name = name
        self.height = height
 
    def sayGreeting(self):
        print "Hello!  My name is", self.name,
        print "I am", self.height, "feet tall!"
						 

Functional Programming

 
>>> def better_outer():
...     count = [0]
...     def inner():
...         count[0] += 1
...         return count[0]
...     return inner
...
>>> counter = better_outer()
					 

dynamic languages

 
// print the integers from 1 to 9
for (int i = 1; i < 10; i++)
{
   System.out.println(i);
}
						 

 
# print the integers from 1 to 9
for i in range(1,10):
    print i
						 

Simplicity of script programming language

On Code comparison with Java

 
import java.io.*;
...

BufferedReader myFile =
    new BufferedReader(
        new FileReader(argFilename));


						 

 
# open an input file
myFile = open(argFilename)							
							
						 

How about this?

 
import java.net.URL;
import java.net.HttpURLConnection;
import java.io.DataOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.BufferedReader;

public class java_post {

public static void main (String args[]) throws Exception {
    System.out.println(
        executePost("http://www.smh.com.au/execute_search.html",
                    "text=fluoride")
    );
}

public static String executePost(String targetURL, String urlParameters){
    URL url;
    HttpURLConnection connection = null;
    try {
        //Create connection
        url = new URL(targetURL);
        connection = (HttpURLConnection)url.openConnection();
        connection.setRequestMethod("POST");
        connection.setRequestProperty("Content-Type",
                                      "application/x-www-form-urlencoded");
        connection.setRequestProperty("Content-Length", "" +
               Integer.toString(urlParameters.getBytes().length));
        connection.setRequestProperty("Content-Language", "en-US");
        connection.setUseCaches (false);
        connection.setDoInput(true);
        connection.setDoOutput(true);

        //Send request
        DataOutputStream wr = new DataOutputStream (
                  connection.getOutputStream ());
        wr.writeBytes (urlParameters);
        wr.flush ();
        wr.close ();

        //Get Response    
        InputStream is = connection.getInputStream();
        BufferedReader rd = new BufferedReader(new InputStreamReader(is));
        String line;
        StringBuffer response = new StringBuffer();
        while((line = rd.readLine()) != null) {
            response.append(line);
            response.append('\r');
        }
        rd.close();
        return response.toString();
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    } finally {
        if(connection != null) {
            connection.disconnect();
        }
    }
  }
}						 

 import urllib, urllib2
data = urllib.urlencode({
                'text' : 'fluoride',
        })
req = urllib2.Request('http://www.smh.com.au/execute_search.html', data)
response = urllib2.urlopen(req)
print response.read()						
						 

python data abstraction

 
public Vector aList = new Vector;
public int    aNumber      = 5;
public int    anotherNumber;

aList.addElement(aNumber);
anotherNumber = aList.getElement(0);

						 

 
aList = []
aNumber = 5

aList.append(aNumber)
anotherNumber = aList[0]
						 

High performance! - Speed

High performance! - Memory Usage

Battery Included

• Large standard library
• Internet-facing applications
• Modules for creating graphical user interfaces
• Modules for connecting to relational databases
• Modules for rithmetic with arbitrary precision decimals
• Modules for Manipulating regular expressions
• Modules for doing unit testing

Why Python?

For productivity

Google Likes Pyhton

Even Sublime text2 !

Extansion As Glue Language

How Python?

Version ?

• 2.X
• 3.X

=> 2.X ! For modules dependencies

Implementations

• CPython : The main Python implementation
• PyPy : fastest just-in-time compiler
• Stackless Python : allowing massively concurrent programs
• Psyco : specialising just in time compiler
• Jython : compiles into Java byte code , Run on JVM
• IronPython : to run Python programs on the .NET Common Language Runtime

unrestricted Python, a restricted subset of Python langauge

• Cython : compile to C
• Pyrex : compile to C
• RPython : compiled to C, Java bytecode or Common Intermediate Language
• Shed Skin : compiles Python to C++
• Pyjamas : compiles Python to JavaScript

Installation

 
.configure
make install
make

or

apt-get install python
						 

 
brew install python
						 

Open Console or Execute Batch File

Python 2.7 (r27:82525, Jul  4 2010, 09:01:59) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

Date Structure on Python

1. 숫자형 (Number)
2. 튜플 (tuple)
3. 리스트 (List)
4. 문자열 (String)
5. 딕셔너리 (Dictionary)
6. 참과 거짓 (Boolean)

숫자형 (Number) Data type

정수          123, -345, 0
실수          123.45, -1234.5, 3.4e10
복소수        1 + 2j, -3j
8진수         034, 025
16진수        0x2A, 0xFF 
						

숫자형 (Number) Data type

>>> a = 1+2j
>>> a.real
1.0
>>> a.imag
2.0
>>> a.conjugate()
(1-2j)
						

리스트 (List) Data type

"[ ]" with ","

>>> a = []
>>> a = [1, 2, 3]
>>> c = ['Life', 'is', 'too', 'short']
>>> d = [1, 2, 'Life', 'is']
>>> e = [1, 2, ['Life', 'is']]
>>> a[0]
1
						

>>> a = [1, 2, 3]
>>> a[2] = 4 # Modified
>>> del a[1] # delete it.
>>> a
[1, 4]
						

List : Can Change. Editable.

리스트 (List) Data type

>>> a = [1, 2, 3]
>>> a[0]
1
>>> a[0] + a[2]
4
>>> a[-1]
3
						

리스트 (List) Data type

l = range(10)
print l

print list1[0] # get ITEM.
list1[0] = -1 # write ITEM.
print len(list1) # length

# addtion.
list1.append(1)
list1.extend([1,2,3])

#sorting
list1.sort()
list1.reverse()

#insert and delete.
list1.insert(3,"hello")
del list1[3]			

리스트 (List) Data type

>>> a = [1, 2, ['a', 'b', ['Life', 'is']]]
>>> a[2][2][0]
'Life'
						

리스트 (List) Data type

>>> a = [1, 2, 3, 4, 5]
>>> a[0:2]
[1, 2]
>>> a = [1, 2, 3, 4, 5]
>>> b = a[:2]
>>> c = a[2:]
>>> b
[1, 2]
>>> c
[3, 4, 5]
						

리스트 (List) Data type

>>> a = [1, 2, 3]
>>> b = [4, 5, 6]
>>> a + b
[1, 2, 3, 4, 5, 6]

>>> a = [1, 2, 3]
>>> a * 3
[1, 2, 3, 1, 2, 3, 1, 2, 3]
						

리스트 (List) Data type

>>> a = [1, 2, 3] 
>>> a.append(4)
>>> a
[1, 2, 3, 4]

>>> a = [1, 4, 3, 2]
 >>> a.sort()
>>> a
[1, 2, 3, 4]

>>> a = [1,2,3,1,2,3]
>>> a.remove(3)
[1, 2, 1, 2, 3]

>>> a = [1,2,3,1]
>>> a.count(1)
2					

리스트 (List) Data type

Hong-Jun-Choiui-MacBook-Pro:~ teemo$ python
Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49) 
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> range(10)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> range(10,0,-1)
[10, 9, 8, 7, 6, 5, 4, 3, 2, 1]
>>> 




							
							
						

튜플 (tuple) Data type

>>> t1 = ()
>>> t2 = (1,)
>>> t3 = (1,2,3)
>>> t4 = 1,2,3
>>> t5 = ('a', 'b', ('ab', 'cd'))
>>> t1 = (1, 2, 'a', 'b')
>>> t1[0]
1
>>> t1[3]
'b'
						

Tuple : Can't Change. Read Only.

문자열 (String) Data type

>>> food = "Python's favorite food is perl"
>>> food = 'Python's favorite food is perl'
>>> say = '"Python is very easy." he says.'
>>> multiline="""Life is too short
		You need python
		Python is powerful language"""
						

문자열 (String) Data type

>>> head = "Python"
>>> tail = " is fun!"
>>> print head + tail
Python is fun!

>>> a = "python"
>>> print a * 2
pythonpython						

문자열 (String) Data type

>>> a = "20010331Rainy"

>>> date = a[:8]
>>> weather = a[8:]

>>> date
'20010331'

>>> weather
'Rainy'
						

문자열 (String) Data type

>>> print "I have %s apples" % 3
I have 3 apples
>>> print "Todays rate is %s" % 3.234
Todays rate is 3.234
						

문자열 (String) Data type

>>> a = "Python is best choice"
>>> a.find('b')
10

>>> a = "Life is too short"
>>> a.split()
['Life', 'is', 'too', 'short']

>>> a = "a:b:c:d"
>>> a.split(':')
['a', 'b', 'c', 'd']

>>> a = "Life is too short"
>>> a.replace("Life", "Your leg")
'Your leg is too short'
						

딕셔너리 (Dictionary) Data type

>>> dic = {'name':'pey', 'phone':'0119993323', 'birth': '1118'}
>>> a = { 'a': [1,2,3]}
>>> grade = {'pey': 10, 'julliet': 99}
>>> grade['pey']
10
>>> grade['julliet']
99
>>> a = {1: 'a'}
>>> a[2] = 'b'
>>> a
{2: 'b', 1: 'a'}
						

참과 거짓(Boolean) Data type

("", [], (), {}, NULL, 0) 중 하나 이면 False,

이외에는 Ture!
						

4줄 요약.

• 숫자 : number1 = 3.14
• 튜플 : tuple1 = (1,2,3)
• 리스트 : List1 = [1,2,3]
• 문자열 : string1 ='hi', string2 = "bye"

이 외에도 다른 자료형이 존재합니다.

• Byte Arrays
• Sets
• Frozen sets
• Callable types
• NotImplemented

Indentation 들여쓰기

### C++ ###
int sum(int a, int b){
	
	int c = a + b;

	return c;
}

### Python ###
def sum(a,b):
	c = a + b
	return c			

Indentation 들여쓰기

if <조건문>:
    <수행할 문장1>
<수행할 문장2>
    <수행할 문장3>
						

if <조건문>
    <수행할 문장1>
    <수행할 문장2>
      <수행할 문장3>
						

Syntax in Conditions

>>> money = 2000
>>> watch = 1
>>> if money >= 3000 or watch:
...     print "택시를 타고 가라"
... else:
...     print "걸어가라"
...
택시를 타고 가라
>>>
						

>>> 1 in [1, 2, 3]
True
>>> 1 not in [1, 2, 3]
False
						

Syntax in Conditions

>>> a = 2
>>> 1 < a < 3
True
>>> 
						

제어문

if문

If <조건문>:
    <수행할 문장1> 
    ...
elif <조건문>:
    <수행할 문장2>
    ...
elif <조건문>:
    <수행할 문장3>
    ...
...
else:
   <수행할 문장4>
   ... 
						

while문

while <조건문>:
    <수행할 문장1>
    <수행할 문장2>
    <수행할 문장3>
    ...
						

coffee = 10
while 1:
    money = int(raw_input("돈을 넣어 주세요: "))
    if money == 300:
        print "커피를 줍니다."
        coffee = coffee -1
    elif money > 300:
        print "거스름돈 %d를 주고 커피를 줍니다." % (money -300)
        coffee = coffee -1
    else:
        print "돈을 다시 돌려주고 커피를 주지 않습니다."
        print "남은 커피의 양은 %d개 입니다." % coffee
    if not coffee:
        print "커피가 다 떨어졌습니다. 판매를 중지 합니다."
        break
						

for문

for 변수 in 리스트(또는 터플, 문자열):
    <수행할 문장1>
    <수행할 문장2>
    ...
						

>>> a = range(10) 
>>> a 
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]  
						

>>> sum = 0 
>>> for i in range(1, 11): 
. . .     sum = sum + i 
. . . 
>>> print sum 
55
						

함수

#!/usr/bin/python
# -*- coding: cp949 -*-


# 가장 간단한 함수 정의
def example():
  print "안녕하세요"


# 함수 호출
example()
# 출력 결과: 안녕하세요




# 함수 인수(매개변수;파라미터)와 반환값 사용
def example2(x, y):
  z = x + y
  return z


# 함수 호출
print example2(2, 3)
# 출력 결과: 5 			

클래스

 
class 클래스이름 [(상속 클래스명)]:
    <클래스 변수 1>
    <클래스 변수 2>
    ...
    def 클래스함수1(self [, 인수1, 인수2, ...]):
        <수행할 문장 1>
        <수행할 문장 2>
        ...
    def 클래스함수2(self [, 인수1, 인수2, ...]):
        <수행할 문장 1>
        <수행할 문장 2>
        ...
    ...
						 

클래스

 
속성	유형	읽기/쓰기	설명
__dict__	사전	R/W	클래스 이름 공간.
__name__	문자열	R/O	클래스의 이름.
__bases__	클래스를 담은 터플	R/O	이 클래스가 상속받은 클래스들.
__doc__	문자열 혹은 None	R/W	클래스 문서화 문자열.
__module__	문자열	R/W	이 클래스가 정의된 모듈의 이름.

						 

클래스

 
# 클래스 선언
class Guest:
    category = 'Guest'   # 클래스 내 변수 설정

    def __init__(self, num): # 생성자 / 객체 생성시 호출되며, GuestID 필요로 한다
         self.GuestID = num
 
    def __del__(self):   # 소멸자 / 객체 소멸시 호출
         print "Guest out"
 
    def printID(self):   # 메소드 / 인스턴스의 GuestID를 출력하는 메소드
         print self.GuestID


						 

클래스

 
# Guest 클래스의 인스턴스 생성, 값 출력, 메소드 호출
A = Guest(3)     # 인스턴스 생성 (GuestID = 3으로 설정)
print A.category    # 인스턴스 내 변수 category 값 출력
print A.GuestID     # 인스턴스의 GuestID 값 출력
A.printID()      # 인스턴스의 printID() 메소드 호출



실행 결과: 
Guest
3
3
Guest out
						 

모듈(module)

 
'''
1. 모듈이름 붙이기 싫은 경우 (모듈 내에 특정함수만 사용하는 경우)

import 모듈이름

모듈이름.함수이름
'''

# module1.py 파일
def sum(a,b):
    return a + b

>>> import module1
>>> module1.sum(2,3)
5
					 

모듈

 
'''
2. 모듈이름 불이기 싫은 경우 (모듈 내의 모든 함수 이용하는 경우 - 가장 일반적인 사용 방법)

from 모듈이름 import *
'''

# module1.py 파일
def sum(a,b):
    return a + b

>>> from module1 import *
>>> sum(2,3)
5
					 

모듈

 //내장 함수 dir()은 한 모듈이 정의한 이름들을 알아냅니다. 

>>> import fibo, sys
>>> dir(fibo)
['__name__', 'fib', 'fib2']
>>> dir(sys)
['__displayhook__', '__doc__', '__excepthook__', '__name__', '__stderr__',
 '__stdin__', '__stdout__', '_getframe', 'api_version', 'argv', 
 'builtin_module_names', 'byteorder', 'callstats', 'copyright',
 'displayhook', 'exc_clear', 'exc_info', 'exc_type', 'excepthook',
 'exec_prefix', 'executable', 'exit', 'getdefaultencoding', 'getdlopenflags',
 'getrecursionlimit', 'getrefcount', 'hexversion', 'maxint', 'maxunicode',
 'meta_path', '모듈', 'path', 'path_hooks', 'path_importer_cache',
 'platform', 'prefix', 'ps1', 'ps2', 'setcheckinterval', 'setdlopenflags',
 'setprofile', 'setrecursionlimit', 'settrace', 'stderr', 'stdin', 'stdout',
 'version', 'version_info', 'warnoptions']
					 

유용한 모듈

math, decimal, datetime, time, re.

For IT-types who will be doing file-oriented work: 

glob, fnmatch, os, os.path, tempfile, and shutil.

Database folks must hear about sqlite and json.

Simulation audience may want to hear about random.

Web developers must hear about urllib2 from a client point of view. Also Beautiful Soup and an XML parser of your choice.

Web developers must hear about logging and wsgiref from a server point of view.
						

socket 모듈로 구현한 예제

#!/usr/bin/python           # This is server.py file

import socket               # Import socket module

s = socket.socket()         # Create a socket object
host = socket.gethostname() # Get local machine name
port = 12345                # Reserve a port for your service.
s.bind((host, port))        # Bind to the port

s.listen(5)                 # Now wait for client connection.
while True:
   c, addr = s.accept()     # Establish connection with client.
   print 'Got connection from', addr
   c.send('Thank you for connecting')
   c.close()                # Close the connection
						

socket 모듈로 구현한 예제

#!/usr/bin/python           # This is client.py file

import socket               # Import socket module

s = socket.socket()         # Create a socket object
host = socket.gethostname() # Get local machine name
port = 12345                # Reserve a port for your service.

s.connect((host, port))
print s.recv(1024)
s.close                     # Close the socket when done
						

socket 모듈로 구현한 예제

# Following would start a server in background.
$ python server.py & 

# Once server is started run client as follows:

$ python client.py
						

Got connection from ('127.0.0.1', 48437)
Thank you for connecting
						

Python Internet modules

A list of some important modules which could be used in Python Network/Internet programming.

Protocol	Common function	Port No	Python module
HTTP	Web pages	80	httplib, urllib, xmlrpclib
NNTP	Usenet news	119	nntplib
FTP	File transfers	20	ftplib, urllib
SMTP	Sending email	25	smtplib
POP3	Fetching email	110	poplib
IMAP4	Fetching email	143	imaplib
Telnet	Command lines	23	telnetlib
Gopher	Document transfers	70	gopherlib, urllib
					

유용한 모듈

Twisted

from twisted.internet import protocol, reactor

class Echo(protocol.Protocol):
    def dataReceived(self, data):
        self.transport.write(data)

class EchoFactory(protocol.Factory):
    def buildProtocol(self, addr):
        return Echo()

reactor.listenTCP(1234, EchoFactory())
reactor.run()
						

Examples of Python Applications

example 1

from twisted.web import server, resource
from twisted.internet import reactor

class HelloResource(resource.Resource):
    isLeaf = True
    numberRequests = 0
    
    def render_GET(self, request):
        self.numberRequests += 1
        request.setHeader("content-type", "text/plain")
        return "I am request #" + str(self.numberRequests) + "\n"

reactor.listenTCP(8080, server.Site(HelloResource()))
reactor.run()
 						

example 2

 							
import sys

from twisted.internet import protocol, defer, endpoints, task
from twisted.mail import imap4
from twisted.python import failure

@defer.inlineCallbacks
def main(reactor, username="alice", password="secret",
         strport="ssl:host=example.com:port=993"):
    endpoint = endpoints.clientFromString(reactor, strport)
    factory = protocol.Factory()
    factory.protocol = imap4.IMAP4Client
    try:
        client = yield endpoint.connect(factory)
        yield client.login(username, password)
        yield client.select('INBOX')
        info = yield client.fetchEnvelope(imap4.MessageSet(1))
        print 'First message subject:', info[1]['ENVELOPE'][1]
    except:
        print "IMAP4 client interaction failed"
        failure.Failure().printTraceback()

# This API requires Twisted 12.3 or later, or a trunk checkout:
task.react(main, sys.argv[1:])