Python [Oakfire Wiki]

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====== Python ======
  * [[https://www.python.org | Officail site: python.org]]
  * [[http://nbviewer.ipython.org/github/rasbt/python_reference/blob/master/tutorials/key_differences_between_python_2_and_3.ipynb | Key differences between python2 and 3]]
===== Tips =====
  * 快速开一个静态http服务: 进入文件夹, 然后 ''python -m SimpleHTTPServer 80''
  * In Terminal, type ''pydoc raw_input'' Read what it says about "raw_input". If you're on Windows try ''python -m pydoc raw_input'' instead. Get out of pydoc by typing ''q'' to quit.
  * python为动态语言,与js类似, list,dict等object的''=''赋值在默认为引用. 如果不需要引用, 那么拷贝list用''list2 = list1[:]'',之后list2的改动便与list1无关.
  * python 变快的 9 个技巧：[[https://medium.com/techtofreedom/9-subtle-tricks-to-make-your-python-code-much-faster-50be6dd69a30|9-subtle-tricks-to-make-your-python-code-much-faster]]
    * 拼接字符串的速度, 直接 ''+'' 快于  ''join()'' 快于 ''+='' 一项项加.
    * Faster List Creation: Use “[]” Over “list()” 用 ''[]''来初始化列表
    * Faster Membership Testing: Use a Set Over a List
    * Faster Data Generation: Use Comprehensions Over For Loops  用内包代替循环
    * Faster Loops: Prioritize Local Variables 优先使用局部变量
    * Faster Execution: Prioritize Built-In Modules and Libraries 优先用内置模块和库
    * Faster Function Calls: Leverage Cache Decorator for Easy Memoization  
    * Faster Infinite Loop: Prefer “while 1” Over “while True” 但是现代解释器基本都优化过， ''while TRUE'' 还更有可读性
    * Faster Start-Up: Import Python Modules Smartly 
===== 从零开始 =====
  * [[http://learnpythonthehardway.org/book/ | learn python the hard way]] python2.
  * Learning more:
      * [[http://learnrubythehardway.org/|Learn Ruby The Hard Way]] You will learn even more about programming as you learn more programming languages, so try learning Ruby too.
      * [[https://docs.djangoproject.com/en/1.4/intro/tutorial01/|The Django Tutorial]] and try to build a web application with the [[https://www.djangoproject.com/|Django Web Framewor]].
      * [[http://www.scipy.org/|SciPy]] if you're into science, math, and engineering and also [[http://dexy.it|Dexy]] for when you want to write awesome papers that incorporate SciPy or any code really.
      * [[http://www.pygame.org/news.html|PyGame]] and see if you can make a game with graphics and sound.
      * [[http://pandas.pydata.org/|Pandas]] for doing data manipulation and analysis.
      * [[http://nltk.org/|Natural Language Tool Kit]] for analyzing written text and writing things like spam filters and chat bots.
      * [[http://docs.python-requests.org/en/latest/index.html|Requests]] to learn the client side of HTTP and the web.
      * [[http://simplecv.org/|SimpleCV]] to play with making your computer see things in the real world.
      * [[http://scrapy.org/|ScraPy]] and try scraping some web sites to get information off them.
      * [[https://www.panda3d.org/|Panda3D]] for doing 3D graphic and games.
      * [[http://kivy.org/|Kivy]] for doing user interfaces on desktops and mobile platforms.
      * [[http://scikit-learn.org/stable/|SciKit-Learn]] for machine learning applications.
      * [[http://renpy.org/|Ren'Py]] for doing interactive fiction games, similar to what you've built in this book but with pictures.
  * Notes:<code python>
# -------------------------------------------------------------------------
# ex1: Print
# -*- coding: utf-8 -*-
print "I'd much rather you 'not'."
print 'I "said" do not touch this.'
print "世界,你好"
# on terminal, run ex1.py
python ex1.py

# -------------------------------------------------------------------------
# ex2: Common
# This is a common
print "common" #This is a common too.

# -------------------------------------------------------------------------
# ex3: Numbers and Math
# + - / * % < > <= >=
# more: **
print "Result is ", 2*2-3/1, "+", 7%6,"=", 2, "is", 2>1, 2**8

# -------------------------------------------------------------------------
# ex4: Variables And Names
cars = 100
space_in_a_car = 4.0

# -------------------------------------------------------------------------
# ex5: More Variables and Printing
my_name = 'lucy'
my_age = 16
print "My name is %s." % my_name
print "My name is %s, i am %d old." % ( my_name, my_age )

# -------------------------------------------------------------------------
# ex6: Strings and Text
print "My name is: %r" % "lucy"  # Print "My name is:'lucy'".
print "My name is: '%s'" % "lucy"  # Print the same.
my_name = "My name is: %r"
print my_name % 'lucy' # Print the same.

# -------------------------------------------------------------------------
# ex7: More Printing
print "a" + "b" + "c" * 5 # Print "abccccc"

# -------------------------------------------------------------------------
# ex8: Printing, Printing
formatter = "%r %r %r %r"
print formatter % (1, 2, 3, 4)
print formatter % ("one", "two", "three", "four")
print formatter % (True, False, False, True)
print formatter % (formatter, formatter, formatter, formatter)

# -------------------------------------------------------------------------
# ex9: Printing, Printing, Printing
# Here's some new strange stuff, remember type it exactly.
days = "Mon Tue Wed Thu Fri Sat Sun"
months = "Jan\nFeb\nMar\nApr\nMay\nJun\nJul\nAug"
print "Here are the days: ", days
print "Here are the months: ", months
print """
There's something going on here.
With the three double-quotes.
We'll be able to type as much as we like.
Even 4 lines if we want, or 5, or 6.
"""
# -------------------------------------------------------------------------
# ex10
print "\t \\ \" '\"' "

# -------------------------------------------------------------------------
# ex11: Asking Questions
print "How old are you?", # We put a "," (comma) at the end of each print line. This is 
#so print doesn't end the line with a newline character and go to the next line.
age = raw_input()
print "So, you're %r old" % age

# -------------------------------------------------------------------------
# ex12: Prompting People
age = raw_input("How old are you ?")

# -------------------------------------------------------------------------
# ex13: Parameters, Unpacking, Variables
from sys import argv
script, first, second, third = argv
print "The script is called:", script
print "Your first variable is:", first
print "Your second variable is:", second
print "Your third variable is:", third

# ex14: Prompting and Passing
# Nothing impresses me.

# -------------------------------------------------------------------------
# ex15: Reading Files
print "Type the filename :"
filename= raw_input("> ")
txt= open(filename)
print txt_again.read()

# -------------------------------------------------------------------------
# ex16: Reading and Writing Files
# class file's function:
# close : like save
# read: 
# seek:
# readline -- Reads just one line of a text file.
# truncate -- Empties the file. Watch out if you care about the file.
# write('stuff')
# writeline
my_file.open('tmp.txt', 'w')
my_file.write('first line \n')

# ex17: More files
# Nothing impresses me.

# -------------------------------------------------------------------------
# ex18: Names, Variables, Code, Functions
# create a function by using the word 'def'
def my_function(*args):
    arg1,arg2=args
    print "arg1:%r, arg2:%r" % (arg1, arg2)
#or
def print_two_again(arg1, arg2):
    print "arg1: %r, arg2: %r" % (arg1, arg2)

# ex19: Functions and Variables 
# ex20: Functions and Files
# ex21: Functions Can Return Something by "return"
# ex22: What Do You Know So Far?
# ex23: Read Some Code
# ex24: More Practice
# Nothing impresses me.

# -------------------------------------------------------------------------
# ex25: Even More Practice
# in ex25.py file:
def break_words(stuff):
    """This function will break up words for us."""
    words = stuff.split(' ')
    return words
# usage ex25.py in Terminal:
import ex25
ex25.break_words("Hello world") # call function 'break_words' in ex25.py
help(ex25) # show help info about ex25.py
help(ex25.break_words) # show help info about function break_words in module ex25
# Typing 'ex25' is annoying. A shortcut is to 
# do your import like this: 'from ex25 import * ' which is like saying, "Import everything from ex25."
from ex25 import *
break_words("Hello world")

# ex26: Congratulations, Take a Test!
# Nothing.

# -------------------------------------------------------------------------
# ex27: Memorizing Logic
# terms:
and, or, not, !=, ==, >=, <=, True, False
 
# ex28: Boolean Practice
# Nothing impresses me.

# -------------------------------------------------------------------------
# ex29: What If
# ex30: Else and If
# ex31: Making Decisions
people = 20
cats = 30
if cars > people:
    print "We should take the cars."
elif cars < people:
    print "We should not take the cars."
else:
    print "We can't decide."

# -------------------------------------------------------------------------
# ex32: Loops and Lists
the_count = [1, 2, 3, 4, 5]
fruits = ['apples', 'oranges', 'pears', 'apricots']
change = [1, 'pennies', 2, 'dimes', 3, 'quarters']
# this first kind of for-loop goes through a list
for number in the_count:
    print "This is count %d" % number
for fruit in fruits:
    print "A fruit of type: %s" % fruit
# also we can go through mixed lists too
# notice we have to use %r since we don't know what's in it
for i in change:
    print "I got %r" % i
# we can also build lists, first start with an empty one
elements = []
# then use the range function to do 0 to 5 counts
for i in range(0, 6):
    print "Adding %d to the list." % i
    elements.append(i)
# now we can print them out too
for i in elements:
    print "Element was: %d" % i

# -------------------------------------------------------------------------
# ex33: While Loops
i = 0
numbers = []
while i < 6:
    numbers.append(i)
    i += 1;
for num in numbers:
    print num
    
# ex34: Accessing Elements of Lists
# Nothing impresses me.

# -------------------------------------------------------------------------
# ex35: Branches and Functions
from sys import exit
def gold_room():
    print "This room is full of gold.  How much do you take?"
    choice = raw_input("> ")
    if "0" in choice or "1" in choice:
        how_much = int(choice)
    else:
        dead("Man, learn to type a number.")

    if how_much < 50:
        print "Nice, you're not greedy, you win!"
        exit(0)
    else:
        dead("You greedy bastard!")

def dead(why):
    print why, "Good job!"
    exit(0)

# -------------------------------------------------------------------------
# ex36: Designing and Debugging
# ex37: Symbol Review
# ex38: Doing Things to Lists
ten_things = "Apples Oranges Crows Telephone Light Sugar"
print "Wait there are not 10 things in that list. Let's fix that."
stuff = ten_things.split(' ')
more_stuff = ["Day", "Night", "Song", "Frisbee", "Corn", "Banana", "Girl", "Boy"]
while len(stuff) != 10:
    next_one = more_stuff.pop()
    print "Adding: ", next_one
    stuff.append(next_one)
    print "There are %d items now." % len(stuff)
print "There we go: ", stuff
print "Let's do some things with stuff."
print stuff[1]
print stuff[-1] # whoa! fancy
print stuff.pop()
print ' '.join(stuff) # what? cool!
print '#'.join(stuff[3:5]) # super stellar!

# -------------------------------------------------------------------------
# ex39: Dictionaries, Oh Lovely Dictionaries
>>> stuff = {'name': 'lucy', 'age': 16}
>>> print stuff['name']
lucy
>>> stuff[1] = "Wow"
>>> stuff
{1:'Wow', 'age':16, 'name':'lucy'}
>>> del stuff['age']
>>> stuff
{1:'Wow', 'name':'lucy'}
# 
for key, value in stuff.items():
    print "%r : %r" % (key, value)

# -------------------------------------------------------------------------
# ex40: Modules, Classes, and Objects
# Modules Are Like Dictionaries
# Classes Are Like Modules
# Objects are Like Import
# Getting Things from Things
# I now have three ways to get things from things:
## dict style
mystuff['apples']
## module style
mystuff.apples()
print mystuff.tangerine
## class style
thing = MyStuff()
thing.apples()
print thing.tangerine

# A First Class Example:
class Song(object):
    def __init__(self, lyrics):
        self.lyrics = lyrics
    def sing_me_a_song(self):
        for line in self.lyrics:
            print line

happy_bday = Song(["Happy birthday to you",
                   "I don't want to get sued",
                   "So I'll stop right there"])
bulls_on_parade = Song(["They rally around tha family",
                        "With pockets full of shells"])
happy_bday.sing_me_a_song()
bulls_on_parade.sing_me_a_song()

# ex41: Learning To Speak Object Oriented
# ex42: Is-A, Has-A, Objects, and Classes
super

# -------------------------------------------------------------------------
# ex43: Basic Object-Oriented Analysis and Design
# ex44: Inheritance Versus Composition
class Parent(object):
    def override(self):
        print "PARENT override()"
    def implicit(self):
        print "PARENT implicit()"
    def altered(self):
        print "PARENT altered()"
class Child(Parent):
    def override(self):
        print "CHILD override()"
    def altered(self):
        print "CHILD, BEFORE PARENT altered()"
        super(Child, self).altered()
        print "CHILD, AFTER PARENT altered()"

dad = Parent()
son = Child()
dad.implicit()
son.implicit()
dad.override()
son.override()
dad.altered()
son.altered()

# multiple inheritance
class SuperFun(Child, BadStuff):
    pass
# Using super() with __init__
class Child(Parent):
    def __init__(self, stuff):
        self.stuff = stuff
        super(Child, self).__init__()
        
# ex45: You Make a Game  
# Nothing impresses me.   

# -------------------------------------------------------------------------
# ex46: A Project Skeleton   
try:
    from setuptools import setup
except ImportError:
    from distutils.core import setup

# -------------------------------------------------------------------------
# ex47: Automated Testing  
nosetests 
from nose.tools import *
assert_equal
# Test files go in "tests/" and are named "BLAH_tests.py" otherwise "nosetests" won't run them.   


# -------------------------------------------------------------------------
# ex48: Advanced User Input   
# A tuple is nothing more than a list that you can't modify. 
# It's created by putting data inside two "("")" with a comma, like a list:
first_word = ('verb', 'go')
# Exceptions and Numbers
def convert_number(s):
    try:
        return int(s)
    except ValueError:
        return None

# -------------------------------------------------------------------------
# ex49: Making Sentences
# ex50: Your First Website
# ex51: Getting Input from a Browser
# ex52: The Start Of Your Web Game
# Nothing impresses me.


</code>