用python与文件进行交互的方法

#打开f=open('a.txt','r')#通过句柄对文件进行操作read_f=f.read()#关闭文件f.close()with open('a.txt','r') as f:  #不需要关闭

f.close() #回收操作系统打开的文件del f #回收应用程序级的变量

#r,只读模式【默认模式，文件必须存在，不存在则抛出异常】f=open('a.txt',encoding='utf-8')data1=f.read()print(f.readline(),end='')print(f.readlines())

#w,只写模式【不可读；不存在则创建；存在则清空内容】f=open('a.txt','w',encoding='utf-8')f.write('werf')

#a,只追加写模式【不可读；不存在则创建；存在则只追加内容】f=open('a.txt','a',encoding='utf-8')f.write('werf/n')

with open('1.jpg','rb') as f_read:  data=f_read.read()  print(data)

with open('a.txt','rb') as f_read:  data=f_read.read().decode('utf-8') #解码  print(data)

with open('a.txt','wb')as f_write:  f_write.write('adsf'.encode('utf-8'))

'''练习，利用b模式，编写一个cp工具，要求如下：　　1. 既可以拷贝文本又可以拷贝视频，图片等文件　　2. 用户一旦参数错误，打印命令的正确使用方法，如usage: cp source_file target_file'''import sysif len(sys.argv)!=3:  print('usage:cp source_file target_file')  sys.exit()source_file,target_file=sys.argv[1],sys.argv[2]print()with open(source_file,'rb')as f_read,open(target_file,'wb')as f_write:  for line in f_read:    f_write.write(line)

#以文本模式读文件，n代表的是字符的个数with open('a.txt','r')as f_read:  data=f_read.read(6)  print(data)

#以b模式读文件，n代表的是字节的个数with open('a.txt','rb')as f_read:  data=f_read.read(6)  print(data)

# tell：告诉当前光标的位置with open('a.txt','r',encoding='utf-8')as f_read:  data=f_read.read(4)  data1=f_read.tell()  print(data,data1)

# seek：移动光标（0：文件开头默认；1：文件当前光标；2：文件末尾）with open('a.txt', 'r', encoding='utf-8')as f_read:  data = f_read.seek(3)  data1 = f_read.read()  print(data, data1)

# 实现tail功能import timewith open('access.log', 'rb')as f_read:  f_read.seek(0,2)  while True:    line = f_read.readline()    if line:      print(line.decode('utf-8'),end='')    else:      time.sleep(1)

import oswith open('a.txt') as read_f,open('.a.txt.swap','w') as write_f:  for line in read_f:    line=line.replace('alex','SB')    write_f.write(line)os.remove('a.txt')os.rename('.a.txt.swap','a.txt')