重新梳理Python基础（3）

1. python输入raw_input()函数。

a = raw_input() #得到的是字符串
a = int(raw_input()) #如果想得到int，只能这样

如果输入特殊字符，比如\t \n等，会和输入一样输出，%r会输出\\t、\\n，%s会输出\t、\n

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 are %r old, %r tall and %r heavy." % (age, height, weight)
print "So, you are %s old, %s tall and %s heavy." % (age, height, weight)
print "So, you are %d old, %d tall and %d heavy." % (int(age), int(height), int(weight))

输出

How old are you?
\t
How tall are you?
\n
How much do you weight?
111
So, you are '\\t' old, '\\n' tall and '111' heavy.
So, you are \t old, \n tall and 111 heavy.

通常都是这么写的

age = raw_input("How old are you?")
height = raw_input("How tall are you?")
weight = raw_input("How much are you weight?")

print "So, you're %r old, %r tall and %r heavy." % (age, height, weight)

input和raw_input的区别

当输入为纯数字时

• input返回的是数值类型，如int,float
• raw_inpout返回的是字符串类型，string类型

输入字符串为表达式

　　input会计算在字符串中的数字表达式，而raw_input不会。

　　如输入 “57 + 3”:

• • 　　input会得到整数60
  • 　　raw_input会得到字符串”57 + 3”

其实

def input(prompt):
    return (eval(raw_input(prompt)))

2. 在windows中查看doc，可以用如下命令

 python -m pydoc raw_input

3. 运行python脚本的时候输入参数，该如何写。

看代码

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

argv类似于java中的main(String[] args)。但是argv需要指定参数个数，并且运行脚本的时候参数个数要对应，不然会报错。并且第一个参数是python ex13.py 1 1 1中的ex13.py。

如果参数个数不对，输出如下：

E:\SkyDrive\python\the hard way to learn python>python ex13.py 1 2 3 4
Traceback (most recent call last):
  File "ex13.py", line 2, in <module>
    script, first, second, third = argv
ValueError: too many values to unpack

4. 读取文件并打印

在脚本中读取文件，最好把文件名作为脚本的参数，以下是代码

from sys import argv

script, filename = argv

txt = open(filename)
print txt.read()
txt.close()

file_name_again = raw_input("the filename you want to print \n > ")
print open(file_name_again).read()

输出

E:\SkyDrive\python\the hard way to learn python>python ex15.py ex15_sample.txt
This is stuff I typed into a file.
It is really cool stuff.
Lots and lots of fun to have in here.
the filename you want to print
 > ex15_sample.txt
This is stuff I typed into a file.
It is really cool stuff.
Lots and lots of fun to have in here.