NA
Python Programming

kcchung

kcchung@cs.nctu.edu.tw

Outline

  • Python 2 or 3?
  • Environment
  • Data Types
  • Flow Control
  • Input & Output
  • Useful Modules
  • OOP
  • Go Further

Resources

https://url.fit/na-py-git

https://url.fit/na-py-slide

slide

example

 

 

Python 2 or 3?

py 2

  • 2.7 is the last version

 

  • more third-party modules

 

  •  2to3.py

 

py 3

  • present & future

 

  • less third-party modules

 

  • 3to2.py

 

We use
Python 2.

Environment

Linux, FreeBSD, MacOSX​

built-in

pkg install python

Environment

Execution

     $ python na.py
     $ python -c 'print "NA score: 100"'
     $ python -m SimpleHTTPServer 8888

Python is used for?

  • Scientific & Math
  • Web programming
  • Cloud computing
  • Game programming
  • Network programming
  • Hardware/Embedded system design
  • System tools
  • ...

na.py

a simple example

na.py

#! /usr/bin/env python
# -*- coding: utf8 -*-
# file: na.py

def na(score=None):
    if score:
        return 'NA score: %s' % score
    else:
        return 'failed.'

if __name__ == '__main__':
    import sys
    if len(sys.argv) >= 2:
        print na(sys.argv[1])
    else:
        print na()
shebang
encoding
comment
starts a block
4-space indent
__name__ : name of the module

Some help functions

help(), dir()

help()

>>> help('for')

'''
The "for" statement
*******************

The "for" statement is used to iterate over the elements of a sequence
(such as a string, tuple or list) or other iterable object:

   for_stmt ::= "for" target_list "in" expression_list ":" suite
                ["else" ":" suite]

The expression list is evaluated once; it should yield an iterable
object.  An iterator is created for the result of the
"expression_list".  The suite is then executed once for each item
provided by the iterator, in the order returned by the iterator.  Each
item in turn is assigned to the target list using the standard rules
for assignments (see *Assignment statements*), and then the suite is
executed.  When the items are exhausted (which is immediately when the
sequence is empty or an iterator raises a "StopIteration" exception),
the suite in the "else" clause, if present, is executed, and the loop
terminates.

A "break" statement executed in the first suite terminates the loop
without executing the "else" clause's suite.  A "continue" statement
executed in the first suite skips the rest of the suite and continues
with the next item, or with the "else" clause if there is no next
item.

The for-loop makes assignments to the variables(s) in the target list.
This overwrites all previous assignments to those variables including
those made in the suite of the for-loop:

   for i in range(10):
       print(i)
...
'''

dir()

>>> dir([])
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', 
'__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__iter__', '__le__', 
'__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', 
'__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'append', 'clear', 'copy', 'count', 'extend', 
'index', 'insert', 'pop', 'remove', 'reverse', 'sort']

>>> from pprint import pprint
>>> pprint(dir([]))
['__add__',
 '__class__',
 '__contains__',
 '__delattr__',
 '__delitem__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattribute__',
 '__getitem__',
 '__gt__',
 '__hash__',
 '__iadd__',
 '__imul__',
 '__init__',
 '__iter__',
 '__le__',
 '__len__',
 '__lt__',
 '__mul__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__reversed__',
 '__rmul__',
 '__setattr__',
 '__setitem__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 'append',
 'clear',
 'copy',
 'count',
 'extend',
 'index',
 'insert',
 'pop',
 'remove',
 'reverse',
 'sort']

 

 

Data Types

​Numeric

  • Integer
  • Float
  • Long
  • Complex
  • Boolean

​Numeric 

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_numeric.py

print type(1)      # <type 'int'>
print type(0.1)    # <type 'float'>
print type(6 + 2j) # <type 'complex'>
print 1 + 2 * 3    # 7
print 5 / 2        # 2 
print 5 / 2.0      # 2.5
print 2 ** 3       # 8
print 2 ** 100     # 1267650600228229401496703205376L
print 2 ** 0.5     # 1.4142135623730951
print abs(-12345)  # 12345
print round(math.pi, 3) # 3.142

​Numeric 

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_numeric.py

import math

print math.e * math.pi   # 8.539734222673566
print math.floor(1.5)    # 1.0
print math.ceil(1.5)     # 2.0

print 0b101 | 0b10       # 7
print 1 << 5             # 32

print int('20')          # 20
print int('0xF', base=16)# 15
print hex(256)           # '0x100'
print oct(256)           # '0400'
print bin(256)           # '0b100000000'

​Sequence

  • String
  • Unicode
  • Tuple
  • List

​Sequence 

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_list_tuple.py

a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
#idx 0  1  2  3  4  5  6  7  8  9
#  -10 -9 -8 -7 -6 -5 -4 -3 -2 -1

print type([])           # <type 'list'>
print type(())           # <type 'tuple'>
print 7 in a             # True
print 100 in a           # False
print 'c' in 'nctu'      # True
print c                  # [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 100, 100]

b = [100] * 5
print b                  # [100, 100, 100, 100, 100]
print b.count(100)       # 5
c = a + [100, 100]
print c                  # [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 100, 100]

# a[start:stop:step]
print a[2]               # 3
print a[-2]              # 9
print a[2:7]             # [3, 4, 5, 6 ,7]
print a[2:7:2]           # [3, 5, 7]
print a[:3]              # [1, 2, 3]
print [6:]               # [7, 8, 9, 10]
print [::3]              # [1, 4, 7, 10]
print [::-1]             # [10, 9, 8, 7, 6, 5, 4, 3, 2, 1]

​Sequence 

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_list_tuple.py

b = [100] * 5
b.append(7)
print b                  # [100, 100, 100, 100, 100, 7]
b.pop()
print b                  # [100, 100, 100, 100, 100]
b.append([-1])
print b                  # [100, 100, 100, 100, 100, [-1]]
b.extend([7, 8])
print b                  # [100, 100, 100, 100, 100, [-1], 7, 8]
b.insert(0, 7788)
print b                  # [7788, 100, 100, 100, 100, 100, [-1], 7, 8]

(x, y) = (4, 5)
x, y = 4, 5
print x, y               # 4, 5

x, y = y, x              # swap
print x, y               # 5, 4

a = [i for i in range(10)]
print a                  # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
b = [i**2 for i in a]
print b                  # [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
c = [i for i in b if i % 2 == 0]
print c                  # [0, 4, 16, 36, 64]

​Sequence 

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_string.py

print type('')           # <type 'str'>

s = 'NA is very interesting.'
print 'NA' in s          # True
print s[6:9]             # 'ver'
print s[::-1][1:10:3].upper()
s.replace('NA is', 'NA is not')
print s                  # 'NA is not very interesting.'

print s.split()          # ['NA', 'is', 'very', 'interesting.']

print '\t\t\t\t\t www.porn.com \t\t\t'.strip()
print ', '.join('abc')   # 'a, b, c'

# 告白用
print '<3'.join(['I', 'love', 'you'])  # 'I<3love<3you'

​Sequence 

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_string.py

print '{0} {1} {2}'.format('a', 'b', 'c')     # 'a b c'
print '{} {} {}'.format('a', 'b', 'c')     # 'a b c'
print '{1} {2} {0}'.format('a', 'b', 'c')     # 'b c a'

print 'Meet me at ({x}, {y}) on 3pm.'.format(x=24.787724, y=120.997618)

Mapping

  • Dictionary

Set

  • Set

  • Frozen Set

NULL object

  • None

​Dict 

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_dict.py

print type({})           # <type 'dict'>
print type(dict())       # <type 'dict'>
user = {'name': 'ToolMan', 'gender': 'Male', 'age': 20, 'height': 175, 'weight': 70, 'girlfriend': None}
# user = dict(name='ToolMan', gender='Male', age=20, height=175, weight=70, girlfriend=None)
print len(user)          # 6 items
print user['name']       # 'ToolMan'
print 'gender' in user   # True

user['girlfriend'] = 'LeftHand'
print user               # {'name': 'ToolMan', 'gender': 'Male', 'age': 20, 'height': 175, 'weight': 70, 'girlfriend': 'LeftHand'}

print user.keys()        # ['name', 'weight', 'gender', 'age', 'height', 'girlfriend']
print user.values()      # ['ToolMan', '70', 'Male', 19, '175', None]
print user.items()       # [('name', 'ToolMan'), ('weight', '70'), ('gender', 'Male'), ('age', 19), ('height', '175'), ('girlfriend', None)]
for key, value in user.items():
    print key, value

​Dict 

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_dict.py

print type({})           # <type 'dict'>
print type(dict())       # <type 'dict'>
user = {'name': 'ToolMan', 'gender': 'Male', 'age': 20, 'height': 175, 'weight': 70, 'girlfriend': None}
# user = dict(name='ToolMan', gender='Male', age=20, height=175, weight=70, girlfriend=None)
print len(user)          # 6 items
print user['name']       # 'ToolMan'
print 'gender' in user   # True

user['girlfriend'] = 'LeftHand'
print user               # {'name': 'ToolMan', 'gender': 'Male', 'age': 20, 'height': 175, 'weight': 70, 'girlfriend': 'LeftHand'}

print user.keys()        # ['name', 'weight', 'gender', 'age', 'height', 'girlfriend']
print user.values()      # ['ToolMan', '70', 'Male', 19, '175', None]
print user.items()       # [('name', 'ToolMan'), ('weight', '70'), ('gender', 'Male'), ('age', 19), ('height', '175'), ('girlfriend', None)]
for key, value in user.items():
    print key, value

​Set 

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_set.py

print type(set())           # <type 'set'>

attractions = {"湯圍溝溫泉公園", "蘭陽博物館", "頭城和平老街"}
attractions.add("礁溪戶政事務所")
attractions.add("橘之鄉蜜餞形象館")
...
attractions.add("橘之鄉蜜餞形象館")

l = ['樂山拉麵', '火車站阿伯蔥油餅']
gf_attractions = set(l)
attractions = attractions | gf_attractions   # 這樣就不會被罵了
attractions.remove("礁溪戶政事務所")

print attractions   # 看不懂
for attraction in attractions:
    print attraction

None

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_none.py

print type(None)           # <type 'NoneType'>
a = None
print a is None            # True
print '100' is not None    # True

if condition:
    print 'Hang out with me!'
else:
    print 'bye'

# | means OR, not an operator.
condition = None | False | [] | '' | {} | set() | 0 | 0.0

 

 

Flow Control

if

statement

if condition_1:
    # do something
elif condition_2:
    # do something
elif condition_3:
    # do something
else:
    # do something
for

statement

for item in iterable:
    # do something
while

statement

while expression:
    # do something
break,continue,pass
Loop:
    if condition:
        break
    
    if condition:
        continue
    
    if condition:
        pass
break,continue,pass
#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_break_continue_pass.py

import random

while True:
    value = random.randint(0, 99)
    if value % 24 == 0:
        print 'My parents are not home.'
        break
Loop:
    # do something
else:
    # do something
else

statement

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_else.py

homeworks = ['na_%s' % str(i) for i in range(1,50)]

for homework in homeworks:
    do_your_homework()
else:
    tell_mom()
else

statement

try:
    # do something
except SomeError:
    # do something
except SomeAnthorError:
    # do something
else:
    # do something
finally:
    # do something
try

statement

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_try.py

import MySQLdb

try:
    db = MySQLdb.connect(host="localhost", user="root", passwd="db_pass", db="db_name")
except Exception as e:
    print e
else:
    cursor = db.cursor()
    cursor.execute('select * from table')
    rows = cursor.fetchall()
finally:
    db.close()
try

statement

def function(x, y=2):
    return x, y

def function(*args):
    return args

def function(**kargs):
    return kargs
def

statement

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_def.py

def fib2(n):
    """Return a list containing the Fibonacci series up to n."""
    result = []
    a, b = 0, 1
    while a < n:
        result.append(a)
        a, b = b, a+b
    return result
def

statement

 

 

Input & Output

print

statement

print 'Hello, world'
# Hello, world
print "Hi I'm %s" % 'jay'
# Hi i'm jay
print 'What\'s up?'
# What's up?
print 'See', 'you', 'soon'
# See you soon
raw_input

function

'''
raw_input([prompt])
'''

price = raw_input("How much?")
print "It's " + price

print "It's " + price*0.7 # invalid
print "It's " + int(price)*0.7 
open

function

'''
file object = open(file_name 
    [, access_mode]
    [, buffering]
)
'''

fin = open('/etc/rc.conf', 'r')
content = fin.read()
fin.close()

context manager

with open('/etc/rc.conf', 'r') as fin:
    for line in fin:
        print line
# file is automatically closed

 

 

Useful Modules

import
# standard library
import math

# a python file(na.py) as a module
import na

from pprint import pprint
pprint(dir(math))

pip
# https://bootstrap.pypa.io/get-pip.py

python get-pip.py

csv
#! /usr/bin/env python
# -*-coding: utf8 -*-
# file: na_csv.py

import csv

with open('file.csv', 'r') as fin:
    for line in csv.reader(fin):
        print line
os.path
#! /usr/bin/env python
# -*-coding: utf8 -*-
# file: na_os_path.py

import os

def list_paths(path):
    paths = []
    for dir_path, dir_names, file_names in os.walk(path):
        for file_name in file_names:
            paths.append(os.path.join(dir_path, file_name))
    return paths

if __name__ == '__main__':
    target = '/etc'
    for path in list_paths(target):
        print path
re
#! /usr/bin/env python
# -*-coding: utf-8 -*-
# file: na_re_search.py

import re

timestamp = 'Sun Mar 24 21:34:34 CST 2016'
r = re.search('\d+:\d+:\d+', timestamp)
print '{}-{} matched: {}'.format(r.start(), r.end(), r.group(0))

r = re.search('(\d+):(\d+):(\d+)', timestamp)
print 'hour=%s, minute=%s, second=%s' % (r.group(1), r.group(2), r.group(3))
re
#! /usr/bin/env python
# -*-coding: utf-8 -*-
# file: na_re_split_findall.py

import re

timestamp = 'Sun Mar 24 21:34:34 CST 2016'
r = re.split('\W', timestamp)
print r
# ['Sun', 'Mar', '24', '21', '34', '34', 'CST', '2016']

r = re.findall('\w+s', 'raining cats & dogs')
print r
# ['cats', 'dogs']
*requests
#! /usr/bin/env python
# -*-coding: utf-8 -*-
# file: na_requests.py

import re
import requests

url = 'https://www.ptt.cc/bbs/Gossiping/M.1456150026.A.855.html'
r = requests.get(url)
print r.text

'''
<div class="bbs-screen bbs-content center clear">
    <form action="/ask/over18" method="post">
        <input type="hidden" name="from" value="/bbs/Gossiping/M.1456150026.A.855.html">
        <button class="btn-big" type="submit" name="yes" value="yes">我同意，我已年滿十八歲<br><small>進入</small></button>
        <button class="btn-big" type="submit" name="no" value="no">未滿十八歲或不同意本條款<br><small>離開</small></button>
    </form>
</div>
'''
*requests
#! /usr/bin/env python
# -*-coding: utf-8 -*-
# file: na_requests.py

import re
import requests

url = 'https://www.ptt.cc/bbs/Gossiping/M.1456150026.A.855.html'
r = requests.get(url, cookies={'over18': '1'})

import re
title = re.findall('<title>(.*?)</title>', r.text)[0]
print title
# [問卦] 台大如果有妹妹系要幾級分? - 看板 Gossiping - 批踢踢實業坊
subprocess
#! /usr/bin/env python
# -*-coding: utf-8 -*-
# file: na_subprocess_call.py

import subprocess

return_code = subprocess.call(['ls', '-al'])
print return_code
# 0
subprocess
#! /usr/bin/env python
# -*-coding: utf-8 -*-
# file: na_subprocess_check_ouput.py

import subprocess

output = subprocess.check_output(['ls', '-al'])
print output

'''
total 4148360
drwxr-xr-x+ 36 jaychung  staff        1224  2 22 13:55 .
drwxr-xr-x+ 81 jaychung  staff        2754  2 22 21:54 ..
-rwxr-xr-x@  1 jaychung  staff        8196  2  1 15:39 .DS_Store
-rwxr-xr-x   1 jaychung  staff           0  2  7  2015 .localized
-rw-r-----@  1 jaychung  staff     1517152 12 11 12:42 416308.pdf
-rw-r-----@  1 jaychung  staff     4173323 11  5 21:14 OReilly.Web.Scraping.with.Python.2015.6.pdf
-rw-r-----@  1 jaychung  staff      896727 12 23 10:41 WWW簡介.pdf
drwxr-xr-x  18 jaychung  staff         612  1 19 21:38 api
drwxr-xr-x  11 jaychung  staff         374  2 19 20:32 cscc
-rw-r--r--@  1 jaychung  staff      296703 11 25 12:39 dooooor.pdf
-rw-r--r--@  1 jaychung  staff       28893 12 21 17:55 fb.jpg
drwxr-xr-x@ 11 jaychung  staff         374 11 10 15:23 garand-sticky-1643193
-rw-r--r--@  1 jaychung  staff      396752 12 23 10:16 msdn.key
-rw-r-----@  1 jaychung  staff      234165  7 13  2015 multigon_3d_wallpaper_by_momkay-wallpaper-1440x900.jpg
-rw-r--r--   1 jaychung  staff         170  2 22 21:54 na_os_path.py
-rw-r--r--@  1 jaychung  staff      793579  2 19 21:55 na_python_prog.key
drwx------@  6 jaychung  staff         204 12 23 16:48 neon-bootstrap-admin-theme
drwxr-xr-x  27 jaychung  staff         918  1  7 14:49 recommender-letter
-rw-r-----@  1 jaychung  staff     4392933 11 18 10:56 shutterstock_219087994.jpg
drwxr-xr-x@ 13 jaychung  staff         442  9 15 06:23 smooth-scroll-master
drwxr-xr-x   7 jaychung  staff         238  1  4 16:23 temp
drwxr-xr-x  18 jaychung  staff         612  2 12 01:23 urlfit
-rw-------@  1 jaychung  staff         165  1 13 23:33 ~$Hw6_LDAP Puppet Jail.pptx
-rw-------@  1 jaychung  staff         162 10 31 01:52 ~$PP-Homework-1.docx
-rw-------@  1 jaychung  staff         171 11 24 20:48 ~$unique_count_ingredients.xlsx
-rw-r--r--@  1 jaychung  staff      283498 12 20 21:52 螢幕快照 2015-12-20 下午9.52.28.png
-rw-r--r--@  1 jaychung  staff      288724 12 20 21:52 螢幕快照 2015-12-20 下午9.52.42.png
-rw-r--r--@  1 jaychung  staff      158020  1 31 19:31 螢幕快照 2016-01-31 下午7.31.40.png
-rw-r--r--@  1 jaychung  staff      157932  1 31 19:33 螢幕快照 2016-01-31 下午7.33.33.png
-rw-r--r--@  1 jaychung  staff       97399  2  3 19:07 螢幕快照 2016-02-03 下午7.07.41.png
-rw-r--r--@  1 jaychung  staff      123172  2  3 19:13 螢幕快照 2016-02-03 下午7.13.23.png
-rw-r--r--@  1 jaychung  staff     1640994  2  4 20:42 螢幕快照 2016-02-04 下午8.42.35.png
-rw-r--r--@  1 jaychung  staff      665149  2 19 23:19 螢幕快照 2016-02-19 下午11.19.38.png
-rw-r--r--@  1 jaychung  staff       94652  2 19 00:41 螢幕快照 2016-02-19 上午12.41.21.png
-rw-r--r--@  1 jaychung  staff  2039989033  2 20 13:52 万万没想到.Surprise.2015.HD1080P.X264.AAC.mp4
-rw-r-----@  1 jaychung  staff    67658436 11  5 21:07 基于开源工具的数据分析.pdf
'''
subprocess
#! /usr/bin/env python
# -*-coding: utf-8 -*-
# file: na_subprocess_popen.py

import subprocess

process = subprocess.Popen(
	['base64', '-D'],
	stdin=subprocess.PIPE,
	stdout=subprocess.PIPE
)

output = process.communicate(input=b'cHl0aG9uCg==')[0]
print output
# 'python\n'
socket
#! /usr/bin/env python
# -*-coding: utf-8 -*-
# file: na_socket_server.py

import socket

HOST = ''
PORT = 50007

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind((HOST, PORT))
sock.listen(1)
conn, addr = sock.accept()
while True:
	data = conn.recv(1024)
	if not data:
		break
	conn.sendall(data)
conn.close()
socket
#! /usr/bin/env python
# -*-coding: utf-8 -*-
# file: na_socket_client.py

import socket

HOST = ''
PORT = 50007

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((HOST, PORT))
sock.sendall('Hello, world')
data = sock.recv(1024)
sock.close()

print "Received: " + str(data)

 

 

OOP

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_oop.py

class Employee(object):
    ''' Employee class '''
    
    def __init__(self, name, age, salary):
        self._name = name
        self._age = age
        self._salary = salary
        self._expired_at = None

    def __repr__(self):
    	return '<Employee name={} age={} salary={} expired_at={}>'.format(
                self._name, self._age, self._salary, self._expired_at
    	)

if __name__ == '__main__':
    me = Employee('kcchung', 22, 5000)
    me._salary = 10000
    print me
inheritance
self is required
_var : public
__var : private
#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_oop_1.py

class Employee(object):
    ''' Employee class '''
    
    __company = 'NCTU'
    __boss = ['Mike', 'Alice', 'Bob']
    def __init__(self, name, age, salary):
        self._name = name
        self._age = age
        self._salary = salary
        self._expired_at = None

    def annual_salary(self):
        return self._salary * 13.5

    @staticmethod
    def check_boss(name):
        if name in Employee.__boss:
        	print '{} is one of our boss.'.format(name)
        else:
        	print '{} is not one of our boss.'.format(name)

    @classmethod
    def visit(cls, name):
    	print 'Hi {}, you are now at {}.'.format(name, cls.__company)

    def __repr__(self):
    	return '<Employee name={} age={} salary={} expired_at={}>'.format(
                self._name, self._age, self._salary, self._expired_at
    	)

if __name__ == '__main__':
    me = Employee('kcchung', 22, 5000)
    me.visit('jay')
    Employee.check_boss('kcchung')
#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_oop_2.py

class Employee(object):
    ''' Employee class '''
    
    __company = 'NCTU'
    __boss = ['Mike', 'Alice', 'Bob']
    def __init__(self, name, age, salary):
        self._name = name
        self._age = age
        self._salary = salary
        self._expired_at = None

    def annual_salary(self):
        return self._salary * 13.5

    @staticmethod
    def check_boss(name):
        if name in Employee.__boss:
        	print '{} is one of our boss.'.format(name)
        else:
        	print '{} is not one of our boss.'.format(name)

    @classmethod
    def visit(cls, name):
    	print 'Hi {}, you are now at {}.'.format(name, cls.__company)

    def __repr__(self):
    	return '<Employee name={} age={} salary={} expired_at={}>'.format(
                self._name, self._age, self._salary, self._expired_at
    	)

class Manager(Employee):
    ''' NCTU Manager '''
    def __init__(self, name, age, salary, group):
        super(Manager, self).__init__(name, age, salary)
        self._group = group

    # overide
    def annual_salary(self):
        return self._salary * 20

    def __repr__(self):
        return '<Manager name={} age={} salary={} expired_at={} group={}>'.format(
                self._name, self._age, self._salary, self._expired_at, self._group
        )

if __name__ == '__main__':
    me = Manager('kcchung', 22, 10000, 'www')
    print me.annual_salary()

Inheritance, overide

 

 

Go Further

Module & Package

├── example.py
├── module_a.py
└── package
    ├── __init__.py
    ├── module_b.py
    └── module_c.py

1 directory, 5 files

Module & Package

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: example.py

import module_a
print module_a.name                # module_a

import package.module_b
package.module_b.na()              # This is na function.

from package import module_c
print module_c.name                # module_c

Typing

  • static typing
  • dynamic typing
  • weak typing
  • strong typing

Static Typing

  • Check type in compile time
  • Need to give a type to a variable

Dynamic Typing

  • Check type in run time
  • A variable just point to an object

Weak Typing

  • It coverts the type  when operating an unsupported type.
  • 1 + '1'
  • 1 == '1'

Strong Typing

  • Unsupported operation will raise an exception.
>>> 1 + '1'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'int' and 'str'

Lambda

#! /usr/bin/env python
# -*- coding: utf-8 -*-
# file: na_lambda.py

f = lambda x, y: x if x > y else y
print f(2, 3)            # 3

d = {'a': 200, 'b': 400, 'd': '50'}
keys = d.keys()
keys.sort(key=lambda x: d[x], reverse=True)
for key in keys:
    print key, d[key]

lambda [args]: [experssion]

 

 

End

We only cover 10% of Python.

Or ... 5% ?

So, keep learning.
Python is USEFUL.

What's more?

  • Generator, yield
  • Decorator
  • Write your own module
  • Syntax Suggestion: PEP8
  • ...

 

 

Q & A