Python
Ko-Lung Yuan
Why Python?
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Simple and elegant
Good readability
Object-oriented / dynamic(script) language
High productivity
Abundant resources(libraries…)
Active community
Wide range of uses
Embeddable and Extendibility
Interactive Learning / well document
Python’s history
• http://zh.wikipedia.org/wiki/Python
Guido van Rossum
Zen of Python
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Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!
Python之禪
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美麗優於醜陋，明講好過暗諭。
簡潔者為上，複雜者次之，繁澀者為下。
平舖善於層疊，勻散勝過稠密；以致輕鬆易讀。
特例難免但不可打破原則，務求純淨卻不可不切實際。
斷勿使錯誤靜靜流逝，除非有意如此。
在模擬兩可之間，拒絕猜測的誘惑。
總會有一種明確的寫法，最好也只有一種，
但或須細想方可得。
凡事雖應三思後行，但坐而言不如起而行。
難以解釋的實作方式，必定是壞方法。
容易解釋的實作方式，可能是好主意。
命名空間讚，吾人多實用。
蟒之道
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妍優於寢 喻莫如敘 是故簡勝繁 繁勝亂
平舖勝汲營 綿密不如疏俊 唯平易而已
無例外於其例 不獨清於實際
毋默於誤 其惡非務
寧戚戚於尋徑 勿揣揣於模稜
道謀於一 可以得矣
力行者宜立行於當下 利行者長三思而後行
不可說之說不可說 可以道之道可以道
名域鳴於域 可取
How to Get Python
• Official website: http://www.python.org/
Install Python
• Python Interpreter and Libraries
• Linux: sudo apt-get install python3.1-dev
IDLE
• A basic but useful editor for Python
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Text-Indent
Keyword-Highlight
Interactive interface
Easy to test code
First, We should know…
• No semicolon (
• No brace (
;) X
{ })
:
• Using colon ( )
• Using text-Indent
X
O
O
Comment
• Single-line comment (
#)
# This is an example of single-line comment
• Multi-line comment (
“”” “”” )
“””This is an example of multi-line comment
You can write the comment in several lines”””
Variable
• Build variable (
Var = … )
Var = 70
Var = 6.78
Var = “alcom lab”
• No declaration but definition and type
• Naming Rule
• No need to worry about where the variables and
their sizes, all of the details are hided!
Input and Output
• Output (
print() )
print(100)
print(“a=”,a)
• Input (
raw_input( [hint] ) )
raw_input(“name:”)
String
• Using quote (
‘ ’, “ ”, “”” ””” )
s1=‘apple’
s2=“banana”
s3=“””I love you”””
print(s1,s2,s3)
• Strings are unchanged object
• Using escape characters(e.g. /n)
String Operation
• Concatenate(
+)
*n )
Length( len() )
Exist( in )
“alcom”+”lab”
• Repeat(
“go”*3
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len(“three”)
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• Split(
‘a’ in ‘apple’
.split(“string”)
) “abc cde”.split(“ ”)
Mathematic Type
• Integer - no limit
123123123112432532643877698709760909
• Float – Not exact, support science notation
123.456
1.2e-3
• Complex number
1+2j
1.23+34.7+5j
Mathematic Operation
• Basic operation + - * / %
• Floating Point –base on simple one
10/3
50*0.5
10+3j-3j
• Special operation ** //
16**0.5
10.0//3.0
All things in python are objects!
List
• An ordered data structure (Like array)
• Mutable Sequence
• [object 1, object 2, …]
listex = [1, 2.34, ”alcom”, 7+8j]
• Support Nested List
nestlist = [ [1,2,3] , [4.2, “john”], Var]
• Access method
listex[-1]
nestlist[0][2]
List Operation
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Length
Append
Extend
Count
Index
Insert
Pop
Remove
Reverse
Sort
len(nestlist)
listex.append(20)
listex.extend([2,3,4])
[1,1,2,3].count(1)
[1,1,2,3].index(1)
[1,1,2,3].insert(1,1)
[1,1,2,3].pop()
[1,1,2,3].remove()
[1,2,3,4].reverse()
[1,2,3,4].sort()
Dictionary
• Dictionary is a mapping object
Key  value
D = { key1:value1, key2:value2, …}
D[key] = value
D[key]
• Dictionary is unordered
• Set is another unordered data structure
Slice
• S[ i ]
• S[ i : j ]
• S[ i : j : k ]
• Some examples
If else
if
condition:
…
elif condition:
…
else:
…
PS : Text-Indent!!
Logical Operation
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==
!=
< > <= >=
Or
And
Not
Boolean value: True False
For Loop
For Var in container:
…code…
…code…
For Var in range(x):
…code…
…code…
Container
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Container are the iterative objects
List: elements of list
Dictionary: keys of dictionary
Tuple: elements of tuple
File: lines of file
range(x): build a list [0, 1, 2, … ,x-1]
In and List Comprehension
•In is an useful keyword
1. in relation
2. for iteration
if a in “abc”
for a in list:
• List Comprehension
List = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
List2 = [item*10 for item in List]
While Loop
While condition:
…code…
While True:
…code…
Nested Structure
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We can use nested structure in python
For loop
While loop
If elif else
Build-in Function
len()
• Sort: sorted()
• Length:
V.s. object.sort()
Function Factory
• Change object type!
• int( )
• str( )
• float( )
Module / Import / Namespace
• A .py file is a module whose name is same as
the file name
• Use module by import
import sys
• Every module has a namespace of its own
– Original-> (main)
– Import one-> It’s name
User Function
• def funciton_name(parameters[=default value]):
…function description…
• Call function
namespace.function_name(parameters)
namespace.function_name(parameters,
appointed parameter1=value,
appointed parameter2=value, …)
Other important issues
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User Object
File IO (simple demo)
Exception Handling
Pypi
pickle
Strong Python
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APPs
Website(server program)
Linux Shell Script / Linux Managing
Latex
Combine with C/C++
Python with Linux (1/2)
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#!/usr/bin/python
# -*- coding: UTF-8 -*Import os and shutil
os.unlink('data.new.txt')
os.rename('data.txt', 'data.alter.txt')
shutil.copy('data.txt', 'data.new.txt')
shutil.move('data.alter.txt', 'data.txt')
chmod a+x python-script-file
Python with Linux (2/2)
• Run outer program
os.system(“program”)
• Pipeline and get the return value
import popen2
stdout, stdin = popen2.popen2(“ls”)
ostr = stdout.read()
print(ostr)
Python with C/C++
• http://docs.python.org/extending/extending.
html
Python with Latex
• http://www.texample.net/weblog/2008/oct/2
4/embedding-python-latex/
Useful Books
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Head First Python
Dive into Python
Programming in Python3
Python Essential Reference
Learning Python
Useful Websites
• http://ez2learn.com/index.php/pythontutorials
• http://wiki.python.org.tw/
• http://caterpillar.onlyfun.net/Gossip/Python/i
ndex.html
• http://pypi.python.org/pypi