《Python 第一章》基础知识

第一章 基础知识
1.1 简单使用和认识 python
    >>> 2**3 
    >>> pow(2, 3)
    >>> 2+8
    >>> x = input("x: ")
    >>> print 'hello world' 
    >>> print "hello world"
    >>> print 3
    >>> print '3'
    >>> 0xAF
    175
    >>> 010
    8
    >>> abs(-10)
    >>> round(1.0/2.0)   // 把浮点数四舍五入为最简介的整数值
    1.0
  * 模块
  >>> import math
  >>> math.floor(32.9)
  32.0
  >>> math.sqrt(9)
  3.0
  >>>

hello.py $ python2 hello.py

name = raw_input("What is your name?")
print "Hello, " + name + "!"

hello2.py $ chmod u+x hello2.py

#!/usr/bin/python2.7
# you should zhushi
name = raw_input("What your name ? \n")
print "Hello " + name + " !\n"

单引号和双引号

>>> "Let's go"
"Let's go"
>>> '"hello world" she said'
'"hello world" she said'

字符串 (3种方法可以转化之) str, repr, 反引号。 print 与不用 print

>>> '"hello world" she said'
'"hello world" she said'
>>> "hello world"
'hello world'
>>> 10000L
10000L
>>> print "hello world"
hello world
>>> print 10000L
10000
>>> print repr("Hello, world")
'Hello, world'
>>> print repr(10000L)
10000L
>>> print str("Hello world")
Hello world
>>> print str(10000L)
10000
>>>

input 与 raw_input 的区别

>>> raw_input("shuru : ")
shuru : 6
'6'
>>> input("shuru : ")  #默认为合法的python表达式
shuru : 5
5
>>>

长字符串，原始字符串和 Unicode

>>> print '''asddddddjkhasdjkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkaweuwqbxcs'''
asddddddjkhasdjkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkaweuwqbxcs
>>> print """asddddddjkhasdjkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkaweuwqbxcs"""
asddddddjkhasdjkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkaweuwqbxcs
>>> print 'C:\nowhere'
C:
owhere
>>> print r'C:\nowhere'
C:\nowhere
>>> print r'C:\nowhere''\\'    # 解决最后一个字符是 '\' 的情况！ 完美解决
C:\nowhere\
>>> print u'hello, world'      # Unicode 字符串， 在python3.0中，所有的字符串都是 Unicode 字符串
hello, world
>>>

本章小结

*1 算法

*2 表达式

*3 变量

*4 语句

*5 函数

*6 模块 #例如： math模块提供了很多数学函数

*7 程序

*8 字符串

本章涉及的新函数： abs, cmath.sqrt, float(object) 将字符串和数字转换为浮点数，同 int(Object), long(object), help(), math.ceil(number), pow(x, y[,z]), round, str(object)......