Basic Operation Phython basis --- files, integrated use

This article summarizes the file operation and use phython basis, learn together, and common progress

• Phython专栏请参考: Life is short - I learned phython

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I. Introduction File Operations

• What is the file
  
• The role of file
• Some storage is to store them, you can make the next time a program executed directly, without having to re-create a copy, saving time and effort

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II. To read and write files

• (1) write data (write)
• Use write () to write data to a file can be done
• Demo: Create a new file file_write_test.py, to write to the following code:

f = open('test.txt', 'w')
f.write('hello world, i am here!')
f.close()

运行之后会在file_write_test.py文件所在的路径中创建一个文件test.txt,其中数据如下:

• Note: If the file does not exist then create, if there is then emptied first, then write the data.

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• (2) read data (Read)
• Use read (num) can read data from a file, NUM represents the length of the data read from the file (in bytes), if no incoming num, it means that all the data file is read
• Demo: Create a new file file_read_test.py, to write to the following code:

f = open('test.txt', 'r')
content = f.read(5)  # 最多读取5个数据
print(content)

print("-"*30)  # 分割线，用来测试

content = f.read()  # 从上次读取的位置继续读取剩下的所有的数据
print(content)

f.close()  # 关闭文件，这个可以是个好习惯哦

• 运行结果：

hello
------------------------------
 world, i am here!

注意：

如果用open打开文件时，如果使用的"r"，那么可以省略，即只写 open('test.txt')

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• (3) read data (the readlines)
• When read as no argument, the readlines entire contents of file can be read in one time-line manner, and returns a list, where each data row as an element

#coding=utf-8

f = open('test.txt', 'r')
content = f.readlines()
print(type(content))

i=1
for temp in content:
    print("%d:%s" % (i, temp))
    i += 1

f.close()

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• (4) read data (the readline)

#coding=utf-8
f = open('test.txt', 'r')

content = f.readline()
print("1:%s" % content)

content = f.readline()
print("2:%s" % content)

f.close()

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Think about it: If a file is large, such as 5G, should imagine how to read the data file into memory and then deal with it?

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Make a backup file: Three applications 1.

• Task Description : Enter the name of the file, then the program automatically back up files
  
  

# 提示输入文件
oldFileName = input("请输入要拷贝的文件名字:")

# 以读的方式打开文件
oldFile = open(oldFileName,'rb')

# 提取文件的后缀
fileFlagNum = oldFileName.rfind('.')
if fileFlagNum > 0:
    fileFlag = oldFileName[fileFlagNum:]

# 组织新的文件名字
newFileName = oldFileName[:fileFlagNum] + '[复件]' + fileFlag

# 创建新文件
newFile = open(newFileName, 'wb')

# 把旧文件中的数据，一行一行的进行复制到新文件中
for lineContent in oldFile.readlines():
    newFile.write(lineContent)

# 关闭文件
oldFile.close()
newFile.close()

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Related operations IV. File

Sometimes, you need to file rename, delete some operations, python os module has such a function

• Rename the file
• os module rename () can be done to the file rename operation

rename(需要修改的文件名, 新的文件名)

import os
os.rename("毕业论文.txt", "毕业论文-最终版.txt")

• Delete Files
• os module remove () to complete the deletion of files

remove(待删除的文件名)

import os
os.remove("毕业论文.txt")

• Create a folder

import os
os.mkdir("张三")

• Get the current directory

import os
os.getcwd()

• Get a directory listing

import os
os.listdir("./")

• Delete the folder

import os
os.rmdir("张三")

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V. Application 2: Batch modify the file name

• Run the demo process
• Before running the program

• After running the program

• Reference Code

#coding=utf-8
# 批量在文件名前加前缀
import os

funFlag = 1 # 1表示添加标志  2表示删除标志
folderName = './renameDir/'

# 获取指定路径的所有文件名字
dirList = os.listdir(folderName)

# 遍历输出所有文件名字
for name in dirList:
    print name

    if funFlag == 1:
        newName = '[东哥出品]-' + name
    elif funFlag == 2:
        num = len('[东哥出品]-')
        newName = name[num:]
    print newName

    os.rename(folderName+name, folderName+newName)

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• Phython专栏请参考: Life is short - I learned phython

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• Thank you for your reading. May we make progress together