python入门学习笔记_please type the file name of input data

学习书籍：learn python the hard way
操作环境：Windows 7, PowerShell, Notepad++
开始时间：2016/11/23
阅读签到：11/23, 11/25, 11/28, 11/29, 11/30，12/9, 12/10，12/12, 12/13, 12/14， 12/15
阅读进度：exercise 29

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1 打印字符串print

print "Hello World!"    #此处双、单引号均可
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2 注释符

NOTE：[csdn-markdown如何打出#字符-_-|||]

print "Hello World!"   #comments
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3 算术运算符与关系运算符

print "3 / 2 = ", 3 / 2
print "Is 3 greater than 2 ?", 3 > 2
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输出：

3 / 2 =  1
Is 3 greater than 2 ? True
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MORE: 注意此处逗号的连接作用

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4 变量声明、赋值、打印

cars = 20
print cars, "cars available"
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5 格式控制输出

province = "Zhejiang"
city = "Hangzhou"
print "Location: %s" % city
print "Let's talk about %s, %s." % (city, province)
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6 字符串变量赋值、%r格式含义

x = "There are %d types of people." % 10
print "I said: %r." % x
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7 输出相同、连续字符

#exr7
print "Its fleece was white as %s." % 'snow'
print "." * 10      #print 10 dots

print "Terry",      #逗号的连接作用
print "Gump"
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输出：

PS C:\Users\Administrator\Desktop> python.exe .\tst.py
Its fleece was white as snow.
..........
Terry Gump
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8 %r格式控制符

分别作用于双引号字符串和单引号字符串(?)：

#exr8
formatter = "%r %r %r %r"
print formatter % (formatter, formatter, formatter, formatter)
print "%r" % "I don't know why."    #note the ' character
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输出：

PS C:\Users\Administrator\Desktop> python.exe .\tst.py
'%r %r %r %r' '%r %r %r %r' '%r %r %r %r' '%r %r %r %r'
"I don't know why."
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9 两种方法输出多行语句：转义字符\n与三个引号

#exr9
months = "Jan\nFeb\nMar\nApr\nMay\nJun\nJul\nAug"
print "Here are the months: ", months

print """   #三个单引号亦可
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.
"""
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10 三个单引号作用与三个双引号相同

-_-|||

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11 raw_input 接收输入返回字符串

#exr11
print "How old are you?",
age = raw_input()
print "How tall are you?",
height = raw_input()
print "How much do you weight ?",
weight = raw_input()

print "So, you're %r old, %r tall and %r heavy." %(
 age, height, weight)
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MORE:
返回值转换为整型：int(raw_input())
raw_input() 将所有输入视为字符串输入；input()可接受合法的python表达式

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12 raw_input使用提示符或者语句接受字符串

#exr12
age = raw_input("How old are you?")
print age
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输出：

PS C:\Users\Administrator\Desktop> python.exe .\exr12.py
How old are you?22
22
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MORE:
pydoc是python自带的模块，可用于浏览或者生成字符串文档(docstring)。

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13 引入模块&接受参数(待修改)

#ex13
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
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输出：

PS C:\Users\Administrator\Desktop> python.exe .\ex13.py a b c
The script is called: .\ex13.py
Your first variable is: a
Your second variable is: b
Your third variable is: c
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14 使用提示符接收输入

#ex14
from sys import argv

script, user_name = argv
prompt = '> '   #NOTICE

print "Hi %s, I'm the %s script." % (user_name, script)
print "I'd like to ask you a few questions."
print "Do you like me %s?" % user_name
likes = raw_input(prompt)   #NOTICE

print "Where do you live %s?" % user_name
lives = raw_input(prompt)

print "What kind of computer do you have?"
computer = raw_input(prompt)

print """
Alright, so you said %r about liking me.
You live in %r. Not sure where that is.
And you have a %r computer. Nice.
""" % (likes, lives, computer)
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输出：

PS C:\Users\Administrator\Desktop> python.exe .\ex14.py terry
Hi terry, I'm the .\ex14.py script.
I'd like to ask you a few questions.
Do you like me terry?
> yes
Where do you live terry?
> hangzhou
What kind of computer do you have?
> pc

Alright, so you said 'yes' about liking me.
You live in 'hangzhou'. Not sure where that is.
And you have a 'pc' computer. Nice.
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15 打开和读取纯文本文件

#ex15
from sys import argv

script, filename = argv

txt = open(filename)

print "Here's your file %r:" % filename
print txt.read()    #NOTICE "print" before "txt.read()"
txt.close()         #NOTICE

print "Type the filename again:"
file_again = raw_input("> ")

txt_again = open(file_again)

print txt_again.read()
txt_again.close()
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输出：

PS C:\Users\Administrator\Desktop> python.exe .\ex15.py .\ex15.txt
Here's your file '.\\ex15.txt':
Time stands still,
Beauty in all she is.
I have been loving you for a thousand years, I'd love you for a thousand more.
Type the filename again:
> ex15.txt
Time stands still,
Beauty in all she is.
I have been loving you for a thousand years, I'd love you for a thousand more.
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python命令行界面使用open

>>> filename = "ex15.txt"
>>> txt = open(filename)
>>> txt.read()
"Time stands still,\nBeauty in all she is.\nI have been loving you for a thousand years, I'd love you for a thousand more."
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16 读写文件

常用函数列举

open
close
read
readline – 只读取文本文件的一行
truncate – 清空文件
write(stuff) – 写入stuff到文件

#ex16
from sys import argv

script, filename = argv

print "Going to erase %s." % filename
print "If you don't want that, hit CTRL-C (^C)."
print "If you do want that, hit ENTER."

raw_input("?")

print "Opening %s..." % filename
target = open(filename, 'w')

print "Truncating %s..." % filename
target.truncate()

print "Enter 3 lines to write in:"

line1 = raw_input("line 1: ")
line2 = raw_input("line 2: ")
line3 = raw_input("line 3: ")

print "Write these to %s..." % filename

#target.write(line1)
#target.write("\n")
#target.write(line2)
#target.write("\n")
#target.write(line3)
#target.write("\n")
target.write(line1 + "\n" + line2 + "\n" + line3 + "\n")
                #write同时接受多个字符串
print "Done!"

print "Reading to check it out..."
target = open(filename)     #default in 'r' mode
print target.read()
raw_input("Hit ENTER to confirm.")

print("Closing the file...")
target.close()  #疑问：此处open两次，close一次，会有什么隐藏的风险吗？

print "End."
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输出：

PS C:\Users\Administrator\Desktop> python.exe .\ex16.py ex16.txt
Going to erase ex16.txt.
If you don't want that, hit CTRL-C (^C).
If you do want that, hit ENTER.
?
Opening ex16.txt...
Truncating ex16.txt...
Enter 3 lines to write in:
line 1: So cold, isn't it?
line 2: Yeah...Bad weather.
line 3: Get in please.
Write these to ex16.txt...
Done!
Reading to check it out...
So cold, isn't it?
Yeah...Bad weather.
Get in please.

Hit ENTER to confirm.
Closing the file...
End.
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MORE:
open函数有三种打开方式’r’,’w’,’a’以及三种衍生的打开方式’r+’,’w+’,’a+’。
open函数默认打开方式是’r’。
在’w’模式下，写入之前通常进行擦除，防止生成乱码。

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17 对多个文件操作：读写、拷贝等

from sys import argv
from os.path import exists  #引用外部资源

script, from_file, to_file = argv

print "Copying from %s to %s" % (from_file, to_file)

# we could do these two on one line too, how?
#in_file = open(from_file)
#indata = in_file.read()
indata = open(from_file).read()

print "The input file is %d bytes long" % len(indata)

print "Does the output file exist? %r" % exists(to_file)
print "Ready, hit Enter to continue, CTRL-C to abort."
raw_input()

out_file = open(to_file, 'w')
out_file.write(indata)

print "Alright, all done."

out_file.close()
#in_file.close()
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exists()函数用以判断文件是否存在。
len()函数返回文件占用长度。

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18 使用关键字def定义函数

#单个参数
def fun1(arg):
    print "arg: %r" % arg   #函数定义语句均缩进4个字符

#多个参数
def fun2(arg1, arg2):
    print "arg1: %r, arg2: %r" % (arg1, arg2)

#带星号参数代指多个参数
def fun3(*args):
    arg1, arg2 = args
    print "arg1: %r, arg2: %r" % (arg1, arg2)

#无参数
def fun4():
    print "Nothing."
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19 函数的参数传递

包括立即数、变量、表达式等均可。

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20 自定义函数读取文件

成员函数seek()用于定位文件指针。
在print()函数后加上逗号，将取消打印print()自带行尾换行符。

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21 函数返回值

使用return传递返回值

def add(a, b):
    return a + b
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23 互联网源码资源

bitbucket.org
github.com
gitorious.org
launchpad.net
sourceforge.net
freecode.com

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24 使用return同时返回多个值

def fun(a):
    b = a + 100
    c = a * 100
    d = a / 100
    return b, c, d

e = int(raw_input())

f, g, h = fun(e)
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25 字符串处理函数

类成员函数

split(char) 以char作为标志分隔句子得到单词集
pop(index) 返回以首单词（字符串）为基准，index为偏移量（可为负数）的单词（字符串）

def print_last_word(words):
    last_word = words.pop(-1)
    print last_word
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系统函数

sorted(words) 给单词（字符串）排序

python解释器操作

以import加上源文件名（可省略’.py’）实现对其中资源的引用。\
输入变量回车，将直接打印变量值。\
help(srcfile)或者help(srcfile.fun)，从源代码中获取帮助。

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27 逻辑运算符

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28 布尔运算练习

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29 if语句

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由于需要加快进度，终止阅读本书，另寻得《简明Python教程》一书，适宜速读。 12/15

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学习书籍：简明Python教程
签到：12/15, 12/18++

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12/15

使用自然字符串处理正则表达式，否则将需要使用很多的反斜杠。

print r"a regular experssion: \\\"
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反斜杠还可起到连接不同物理行的逻辑行的作用。

print \
"hello world"
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12/18

while循环可以附带一个else从句，尽管很少用到。
for循环根据序列决定循环次数而不是判断条件。也可以附带else从句。

for i in range(1, 5) #此处生成的序列为[1,2,3,4]
    print i
else:
    print 'The for loop is over'
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函数

在函数内使用global语句可以引用函数外的变量。应尽量避免直接使用函数外的变量。

• 默认参数值
  在形参名后加上赋值运算符（=）和默认值，可以给形参指定默认参数值。有默认值的形参必须放在形参表的末尾。
• 关键参数
  使用名字（关键字）而不是位置来给函数指定实参。

def func(a, b=5, c=10):
    print 'a is', a, 'and b is', b, 'and c is', c

func(25, c=24)    
func(c=50, a=100)
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pass语句表示一个空的语句块。

DocStrings文档字符串
文档字符串适用于函数、模块和类。
其惯例是一个多行字符串，它的首行以大写字母开始，句号结尾。第二行是空行，从第三行开始是详细的描述。
对于函数，可以使用__doc__（双下划线）调用printMax函数的文档字符串属性（属于函数的名称）。help()所做的工作即抓取函数的__doc__属性。

模块

import语句可引入模块。
from .. import语句引入模块中的具体标识符。一般应避免使用。

from sys import *   #输入sys模块中的所有标识符
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sys.path第一个字符串是空的，代表当前目录。

模块的name属性 -> MORE
每个Python模块都有它的__name__，如果它是’__main__’，这说明这个模块被用户单独运行，可以进行相应的操作。
dir()返回模块定义的标识符列表。没有参数时返回当前模块中定义的标识符列表。
del语句删除当前模块中的变量/属性。

数据结构

通过[]索引具体项目：list[index]

列表，list类：方括号+用逗号分割项目，可变，序列

append方法：在列表尾添加项目
sort方法：给列表项排序

元组：圆括号+用逗号分割项目，不可变，序列

一个空的元组由一对空的圆括号组成。
含有单个元素的元组必须在第一个（唯一一个）项目后跟一个逗号，这样Python才能区分元组和表达式中一个带圆括号的对象。

字典，dict类的对象：花括号，键（唯一）：值，无序

键值对在字典中以这样的方式标记：d = {key1 : value1, key2 : value2 }。
items方法：返回一个由元组组成的列表，其中每个元组都包含一对项目——键与对应的值
in操作符/has_key方法：检验一个键/值对是否存在

序列

索引操作符

当索引是负数时，位置是从序列尾开始计算的。

切片操作符：序列名后跟一个方括号，方括号中有一对可选的数字，并用冒号（必有）分割。

返回的序列从开始位置开始，在结束位置之前结束。