Python: 文件操作

文件操作

文件操作，无外乎读写，但首先你要打开文件。

打开文件

f = open(filename, mode) filename是文件名，可以带目录；mode是读写模式（可以是读，写，追加等）；f是file handler。

关闭文件

f.close()

模式

• "r": Open a file for read only
• "w": Open a file for writing. If file already exists its data will be cleared before opening. Otherwise new file will be created
• "a": Opens a file in append mode i.e to write a data to the end of the file
• "wb": Open a file to write in binary mode
• "rb": Open a file to read in binary mode

写入文件

注意，write不会自动加入\n，这一点不像print。

f = open('myfile.txt', 'w')    # open file for writing
f.write('this is first line\n')   # write a line to the file
f.write('this is second line\n')  # write one more line
f.close()

读文件

总共有三个模式：

• read([number]): Return specified number of characters from the file. if omitted it will read the entire contents of the file.
• readline(): Return the next line of the file.
• readlines(): Read all the lines as a list of strings in the file

读取所有内容

f = open('myfile.txt', 'r')
f.read()

'this is first line\nthis is second line\n'

f.close()

读取所有行

f = open('myfile.txt','r')
f.readlines()

['this is first line\n', 'this is second line\n']

f.close()

读取一行

f = open('myfile.txt','r')
f.readline()

'this is first line\n'

f.close()

Append

f = open('myfile.txt','a')
f.write('this is third line\n')

f.close()

遍历文件数据

f = open('myfile.txt','r')
for line in f:
    print line,

this is first line
this is second line
this is third line

f.close()

with open

with open('myfile.txt','r') as f:
    for line in f:
        print line,

this first line
this second line
this is third line

with open('myfile.txt','r') as f:
    for line in f.readlines():
        print line,    

this is first line
this is second line
this is third line