Python 文件操作

文件操作的步骤

打开文件

对文件进行操作

关闭文件

打开文件

open("filename" [, mode])

codecs.open("filename"[, mode])

需import codecs 模块 (处理编码转换),推荐使用

两者均返回一个 file 对象

打开方式 Mode(默认只读方式 rb)

r 读

w 写(覆盖)

b 二进制

a 追加

import codecs

file = open("1.txt")
print(type(file))

file1 = codecs.open('1.txt')
print(type(file1))

执行:
C:\Python27\python.exe D:/Python/Study/file-1.py
<type 'file'>
<type 'file'>

Process finished with exit code 0

关闭文件

close()

关闭打开的文件

closed()

检测文件是否关闭 返回布尔值

import codecs

file = codecs.open('1.txt')
print(type(file))
print(file.closed)
file.close()
print(file.closed)

执行:
C:\Python27\python.exe D:/Python/Study/file-1.py
<type 'file'>
False
True

Process finished with exit code 0

with

import codecs
with codecs.open('1.txt') as file:
    print(file.closed)
print(file.closed)

等价于

import codecs

file = codecs.open('1.txt')
print(file.closed)
file.close()
print(file.closed)

操作

test.txt 内容

aaaa
#################
bbbb
@@@@@@@@@@@@@@@@@
cccc
$$$$$$$$$$$$$$$$$
dddd

读文件

file.read()

读取整个文件,返回一个字符串类型(可对其使用字符串的所有方法)

iimport codecs

file = codecs.open("test.txt")
text = file.read()
print(type(text))
print(text)
result = text.replace("a", "1")
print(result)
file.close()
执行:
C:\Python27\python.exe D:/Python/file/file.py
<type 'str'>
aaaa
#################
bbbb
@@@@@@@@@@@@@@@@@
cccc
$$$$$$$$$$$$$$$$$
dddd
1111
#################
bbbb
@@@@@@@@@@@@@@@@@
cccc
$$$$$$$$$$$$$$$$$
dddd

Process finished with exit code 0

file.readlines(self,size=None)

读取所有行,返回一个列表,每一行为列表里的一个元素

readlines([size]) -> list of strings, each a line from the file.

重复调用readline（），并返回所读行的列表。可选的size参数（如果给定）是返回行中总字节数的近似边界。

import codecs

file = codecs.open('test.txt')
text = file.readlines()
print(type(text))
print(text)

file.close()

执行:

C:\Python27\python.exe D:/Python/file/file.py
<type 'list'>
['aaaa\r\n', '#################\r\n', 'bbbb\r\n', '@@@@@@@@@@@@@@@@@\r\n', 'cccc\r\n', '$$$$$$$$$$$$$$$$$\r\n', 'dddd']

Process finished with exit code 0

file.readline(self,size=None) 和 file.next()

file.readline() 逐行读取文件,返回一个字符串

readline([size]) -> next line from the file, as a string.

保留换行符非负大小参数限制返回的最大字节数（然后可能会返回不完整的行）。在EOF返回一个空字符串

import codecs

file = codecs.open('test.txt')
text = file.readline()
print(type(text))
print(file.readline())
print(file.readline())
print(file.readline())
print(text)
# file.next()

file.close()

执行:
C:\Python27\python.exe D:/Python/file/file.py
<type 'str'>
#################

bbbb

@@@@@@@@@@@@@@@@@

aaaa


Process finished with exit code 0

file.next() 读取下行

import codecs

file = codecs.open('test.txt')
print(file.readline())
print(file.next())

file.close()

执行;
C:\Python27\python.exe D:/Python/file/file.py
aaaa

#################


Process finished with exit code 0

写文件

file.write(filename,[wb/ab])
需要传字符串类型的数据

#写入一个文件
import codecs

file = codecs.open('1.txt', 'wb')
# text = file.read()
# print(text)
# print('#' *30)
file.write('this is a test file for python write!!!')
print('#' *30)
file.close()

file = codecs.open('1.txt')
text = file.read()
print(text)
file.close()
执行:
C:\Python27\python.exe D:/Python/file/file.py
##############################
this is a test file for python write!!!

Process finished with exit code 0


#覆盖内容

import codecs

file = codecs.open('1.txt','rb')
text = file.read()
print(text)
file.close()

file = codecs.open('1.txt','wb')
file.write('1.txt已存在,wb模式将覆盖其原有内容')
file.close()

file = codecs.open('1.txt','rb')
text = file.read()
print(text)
file.close()

执行:
C:\Python27\python.exe D:/Python/file/file.py
this is a test file for python write!!!
1.txt已存在,wb模式将覆盖其原有内容

Process finished with exit code 0


# 追究加

import codecs

file = codecs.open('1.txt','rb')
text = file.read()
print(text)
file.close()

file = codecs.open('1.txt','ab')
file.write('这些内容将追加到1.txt中')
file.close()

file = codecs.open('1.txt','rb')
text = file.read()
print(text)
file.close()

执行:
C:\Python27\python.exe D:/Python/file/file.py
1.txt已存在,wb模式将覆盖其原有内容
1.txt已存在,wb模式将覆盖其原有内容这些内容将追加到1.txt中

Process finished with exit code 0

file.writelines()

必须传入一个列表

import codecs

file = codecs.open('2.txt', 'ab')
file.writelines(['123121\n', 'AFSDFA\n', '3424wewersf\n'])
file.close()

file = codecs.open('2.txt', 'rb')
print(file.read())
file.close()

执行:
C:\Python27\python.exe D:/Python/file/file.py
123121
AFSDFA
3424wewersf


Process finished with exit code 0

其它方法

file.tell()

返回文件的当前位置，即文件指针当前位置

import codecs

file = codecs.open('test.txt')
text = file.read()
print(text)
print(file.tell())
file.close()

print('#' * 30)
file = codecs.open('test.txt')
line = file.readline()
print(line)
print(file.tell())
file.close()

执行:
C:\Python27\python.exe D:/Python/file/file.py
aaaa
#################
bbbb
@@@@@@@@@@@@@@@@@
cccc
$$$$$$$$$$$$$$$$$
dddd
79
##############################
aaaa

6

Process finished with exit code 0

file.seek() fileObject.seek(offset[, whence])

用于移动文件读取指针到指定位置 没有返回值。

offset -- 开始的偏移量，也就是代表需要移动偏移的字节数

whence：可选，默认值为 0。给offset参数一个定义，表示要从哪个位置开始偏移；0代表从文件开头开始算起，1代表从当前位置开始算起，2代表从文件末尾算起。

import codecs

file = codecs.open('test.txt')
print(file.readline())
file.seek(0, 0)

print(file.readline())

file.close()

执行:
C:\Python27\python.exe D:/Python/file/file.py
aaaa

aaaa

Process finished with exit code 0

file.name()

import codecs

file = codecs.open('test.txt')
print(file.name)
file.close()
执行:
C:\Python27\python.exe D:/Python/file/file.py
test.txt

Process finished with exit code 0