[Python基础]006.IO操作

IO操作

输入输出
- print
- raw_input
- input
文件
实例

输入输出

输入输出方法都是Python的内建函数，并且不需要导入任何的包就可以使用。

print

简单控制台输出方法 print ...

print 'content'

raw_input

简单的控制台输入方法 raw_input(显示的内容....)

num = raw_input('Please input a number:')   // 输入一个数字

print num

input

同样是输入方法，与raw_input不同的是：raw_input将所有输入作为字符串，返回字符串；而input要求输入的内容是一个合法的Python表达式。如在输入字符串时，要用引号包裹字符串，输入"xxx"。

content = input('Please input a string:')   //输入一个字符串

print content

文件

Python通过一个内建的file类型来操作一个文件。

打开文件

open(文件路径, 读写模式) 或者 file(文件路径, 读写模式) 方法。二者没有区别，都会返回一个file。

fr = open('test.txt', 'r')  # 读模式打开text.txt

fw = file('test.txt', 'w')  # 写模式打开text.txt

读写模式类型有：

r 读模式（默认模式，可以不写）
w 写模式
a 追加模式
r+ 读写模式
w+ 读写模式
a+ 读写模式
rb 二进制读模式
wb 二进制写模式
ab 二进制追加模式
rb+ 二进制读写模式
wb+ 二进制读写模式
ab+ 二进制读写模式

关闭文件

打开文件后要关闭文件。close(文件)

f = open('test.txt')

# 操作文件...

f.close()

读文件

使用file对象的read等方法进行文件的读取。

read 读取
readline 读取一行文件
readlines 读取文件所有行

代码

f = open('test.txt', 'r')

print f.read(10)                # 读取10个字节的数据

print f.read(100)               # 再读取后100个字节的数据

f.close()

# 第一种读取方式

f1 = open('test.txt', 'r')

print f1.read()                 # 不带参数时，读取文件的所有内容

f1.close()

# 第二种读取方式

f2 = open('test.txt')

line = f2.readline()            # 读取文件第一行

while line:

    # 不断读取文件下一行，直到line为空值

    print line

    line = f2.readline()        # 读取文件的下一行

f2.close()

# 第三种读取方式

f3 = open('test.txt')

lines = f3.readlines()          # 讲文件以行为单位做成一个数组返回

for line in lines:

    print line

f3.close()

readline和readlines都不会删除行结尾符\n。
在没有足够内存一次读取整个文件时，就要使用readline。

写文件

使用file对象的write等方法进行文件的写入。

write 写入文件
writelines 写入多行

代码

# 覆盖写入

f = open('test.txt', 'w')

f.write('write it to your file.')   # 写入

f.close()

# 追加写入

f = open('test.txt', 'a')

f.write('write it to your file.')   # 写入

f.close()

# 写入多行

f = open('test.txt', 'w')

content = ['aaaa\n', 'bbbb\n', 'cccc\n', 'dddd\n']

f.writelines(content)               # 写入多行

f.close()

文件指针

文件指针的操作

seek 移动文件指针到不同的位置
tell 显示文件当前指针的位置

代码

f = open('test.txt')

f.readline()

print f.tell()              # 文件指针位置改变

f.seek(0)                   # 文件指针回到起始位置0

print f.tell()

print f.readline()          # 始终打印第一行

实例

下面是一个简单的文件操作实例。

# -*- coding: utf-8 -*-

import os

while True:

    filepath = raw_input('输入要读取的文件路径:')

    if not os.path.exists(filepath):        # 判断文件是否存在

        print '文件不存在'

        continue

    f = open(filepath)

    print f.read()

    f.close()

本站文章为宝宝巴士 SD.Team原创，转载务必在明显处注明：（作者官方网站：宝宝巴士)
转载自【宝宝巴士SuperDo团队】 原文链接: http://www.cnblogs.com/superdo/p/4544859.html

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