open a file
1. Establish a program object file on disk with associated
2. Access to relevant documents by subject
File Operations
(1) read (2) writing (3) Other: adding, computing
Close the file
(1) cut off contact with the program file
(2) written to disk, and releases file buffers
open a file
Open( )
<variable> = open (<name>, <mode>)<name>磁盘文件名
<mode>打开模式
Open mode
'''
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'''
#例如，打开一个名为7.1.txt文件
textfile = open("7.1.txt",'r')
#打开一个music.mp3的音频文件
binfile = open('music.mp3','rb')
After use close the file using () method to close, release the license file format:
<Variable name> .close ()
Read and write files
-
read () Returns a string that contains the value of the contents of the entire file
-
the readline () Returns the value of the contents of the file string of the next line.
-
readlines () Returns the value of the entire contents of the file list, each newline to the end of his string.
#1
fname = input("输入你要打开的文件：")
fo = open(fname,'r')
for line in fo.readlines():
print(line)
fo.close()
#2
with open ("demo1.txt",'r',encoding='utf8')as f:
for line in f.readlines():
print(line,end='')
The code applies only to short code, the disadvantage is: when the file is very large, one-time to read the contents of the list will take up a lot of memory,
Rigid enforcement of speed. Reasonable approach is progressive read into memory, and progressive process. Python file itself as a sequence of rows,
All lines traverse the document.
'''
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'''
fname = input("输入你要打开的文件：")
fo = open(fname,'r')
for line in fo():
print(line)
fo.close()
Write to file
Data is written to the file from the computer's memory
- write (): This article contains a string or binary data blocks written to the file.
- writelines (): For a list of actions to receive a list of strings as arguments, it
had written to the file.
#写法一
fname = input("请输入要写入的文件：")
fo = open(fname,'w+')
lst = ['This is a demo ','and demo']
fo.writelines(lst)
for line in fo:
print(line)
fo.close()
#写法二
lst=['This is a demo ','and demo']
with open ("demo1.txt",'a',encoding='utf8')as f:
for x in lst:
f.write('{}\n'.format(x))
with open ("demo1.txt",'r',encoding='utf8')as f:
for line in f.readlines():
print(line,end='')
Results of the:
