3年前用过Python，现在忘的差不多了，现在项目又用到它了，重新拾起来，记录笔记以方便以后的重拾。

1. Python脚本

脚本提示符：

#! /usr/bin/env python

2. 语言基础

2.1 Numbers

i. Python的整数相除是向上取整

>>> 7/3

2

>>> 7/-3

-3

ii. 复数用(real+imagj)，或complex(real, imag)创建

2.2 Strings

i. 单引号(')和双引号(")均可表示字符串

ii. 多行可以用三个引号(""")标识开始和结束

iii. 常量字符串前加r表示raw字符串，内容将不会转义

>>> rawstring = r'raw string \n \t \r keeps'

>>> print rawstring

raw string \n \t \r keeps

iv. 字符串可以用加号(+)连接(常量字符串之间可以省略)，且可以重复(*)

>>> repeat = 'I' ' Love' * 3 + ' Python'

>>> print repeat

I LoveI LoveI Love Python

v. 字符串切割(slice)

字符串可以被任意切割，如果范围不正确或超过范围返回空字符串，但下标访问超过范围会抛异常

>>> helloworld = 'hello world'

>>>

>>> helloworld[5:]

' world'

>>> helloworld[6]

'w'

>>>

>>> helloworld[6:]

'world'

>>> helloworld[3:5]

'lo'

>>> helloworld[-1]

'd'

>>> helloworld[-2:3]

''

>>> helloworld[:-6]

'hello'

>>> helloworld[-0]

'h'

>>> helloworld[30:]

''

>>> helloworld[1:100]

'ello world'

>>> helloworld[6:2]

''

>>> helloworld[30]

Traceback (most recent call last):

File "", line 1, in

helloworld[30]

IndexError: string index out of range

2.3 Lists

i. Python的List的元素可以不为不同类型

>>> lista = ['egg', 'hurt', 2, 3.14]

>>> lista

['egg', 'hurt', 2, 3.14]

ii. List可以像字符串一样随意切割，重复，下标访问

>>> lista[0:2] + ['very'] * 2

['egg', 'hurt', 'very', 'very']

>>> lista[3]

3.14

iii. List的替换、插入、赋值、清空

>>> lista

['egg', 'hurt', 2, 3.14]

>>>

>>> lista[0:2]=['foo', 1.72] # replacement

>>> lista

['foo', 1.72, 2, 3.14]

>>> lista[0] = [] #add list as an element

>>> lista

[[], 1.72, 2, 3.14]

>>> lista[0:1] = [] #clear elements between 0 and 1

>>> lista

[1.72, 2, 3.14]

>>> lista[1:1] = ['sec', 'third'] #insert two elements at index 1

>>> lista

[1.72, 'sec', 'third', 2, 3.14]

>>> lista[:0] = lista #make a copy of itself

>>> lista

[1.72, 'sec', 'third', 2, 3.14, 1.72, 'sec', 'third', 2, 3.14]

>>> lista[:] = [] #clear

>>> lista

[]

>>> len(lista)

0

2.4 控制流

i. if...elif..else

>>> def whatx(x) :

if x > 0 :

print 'positive'

elif x == 0 :

print 'zero'

else :

print 'negative'

>>> whatx(-3)

negative

ii. for...in

>>> for i in [1, 2, 3, 4, 5] :

print i,

1 2 3 4 5

和其他语言一样在循环的时候添加删除元素是不安全的，Python可以隐式的拷贝一个List

>>> odds = [1, 3, 4, 7]

>>> for i in odds[:] : #make a slice copy of entire list

if (0 == i % 2) :

odds.remove(i)

>>> odds

[1, 3, 7]

iii. Range，可指定起始，步长

>>> range(5)

[0, 1, 2, 3, 4]

>>> range(2, 10)

[2, 3, 4, 5, 6, 7, 8, 9]

>>> range(3, 15, 3)

[3, 6, 9, 12]

>>> range(-5, -30, -5)

[-5, -10, -15, -20, -25]

iv. Pass占位符

Pass什么都不做，只是让语法通过，

>>> class Non :

pass # minimal class for indicate a status

>>> def foo() :

pass # remember implement this

>>>

v. 赋值

Python可以一次给多个变量赋值

>>> x, y, z = 1, 5, 7

>>> x

1

>>> y

5

>>> z

7

vi. == 和is

==相当于equals，而is确定是否是同一对象。

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2012-07-06 16:10

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