#打開f=open('a.txt','r')#通過句柄對文件進行操作read_f=f.read()#關閉文件f.close()with open('a.txt','r') as f:  #不需要關閉

f.close() #回收操作系統打開的文件del f #回收應用程序級的變量

#r,只讀模式【默認模式，文件必須存在，不存在則拋出異常】f=open('a.txt',encoding='utf-8')data1=f.read()print(f.readline(),end='')print(f.readlines())

#w,只寫模式【不可讀；不存在則創建；存在則清空內容】f=open('a.txt','w',encoding='utf-8')f.write('werf')

#a,只追加寫模式【不可讀；不存在則創建；存在則只追加內容】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') #解碼  print(data)

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

'''練習，利用b模式，編寫一個cp工具，要求如下：　　1. 既可以拷貝文本又可以拷貝視頻，圖片等文件　　2. 用戶一旦參數錯誤，打印命令的正確使用方法，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)

#以文本模式讀文件，n代表的是字符的個數with open('a.txt','r')as f_read:  data=f_read.read(6)  print(data)

#以b模式讀文件，n代表的是字節的個數with open('a.txt','rb')as f_read:  data=f_read.read(6)  print(data)

# tell：告訴當前光標的位置with open('a.txt','r',encoding='utf-8')as f_read:  data=f_read.read(4)  data1=f_read.tell()  print(data,data1)

# seek：移動光標（0：文件開頭默認；1：文件當前光標；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)

# 實現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')