一、檔案開啟模式

with open(r'a.txt',mode='wt',encoding='utf-8') as f:
  f.write("你好")
​
with open(r'a.txt',mode='ab') as f:
  f.write("哈哈哈".encode('utf-8'))
​
​
with open(r'a.txt',mode='rb') as f:
  data = f.read()
  print(data.decode('utf-8'))
​
​
with open(r'1.mp4',mode='rb') as f:
  data = f.read()
  print(data)
​
  for line in f:
    print(line)
​
''
with open('1.mp4',mode='rb') as f1,open(r'D:\111111111111.mp4',mode='wb') as f2:
  data = f1.read()
  f2.write(data)
  for line in f1:
    f2.write(line)
 

二、可讀可寫模式

with open('a.txt',mode='r+t',encoding='utf-8') as f:
  f.write('次臥')
  f.write('h')

三、修改檔案的兩種方式

with open('123.txt',mode='wb') as f:
   pass
​
with open('123.mp4',mode='rb') as f1,open('456.mp4',mode='wb') as f2:
   for line in f1:
     f2.write(line)
​
with open('123.txt',mode='rt',encoding='utf-8') as f1:
   date = f1.read()
   res = date.replace('wyf','WYF')
with open('123.txt',mode='wt') as f1:
   f1.write(res)
import os
​
with open('123.txt',mode='rt',encoding='utf-8') as f1,open('.123.txt.swp',mode='wt') as f2:
   date = f1.read()
   res = date.replace('WYF','wyf')
   f2.write(res)
os.remove('123.txt')
os.rename('.123.txt.swp','123.txt')
​
​
inpu_user = input("請輸入你的使用者名稱：")
inpu_pwd = input("請輸入你的密碼：")
inpu_money = input("請輸入你的餘額：")
with open('123.txt',mode='at') as f:
   f.write('%s:%s:%s\n' %(inpu_user,inpu_pwd,inpu_money))
​
​
import os
​
with open('123.txt',mode='rt',encoding='utf-8') as f1,open('.123.txt.swp',mode='wt') as f2:
   for line in f1:
     user,pwd,money = line.strip("\n").split(":")
     if user == "wyf":
       money = int(money)-100
     elif user == "cxk":
       money = int(money)+100
     line = '%s:%s:%s\n'%(user,pwd,money)
     f2.write(line)
​
os.remove('123.txt')
os.rename('.123.txt.swp','123.txt')
​
with open("198.txt",mode="wt") as f:
   print(f.writable())
   f.write('hcuwehfui')
​
with open("198.txt",mode='rt',encoding='utf-8') as f:
   print(f.readable())
   print(f.readline())
 

四、練習（註冊和轉賬）

註冊
​
inp_user = input("請輸入您的用名：").strip()
inp_pwd = input("請輸入您的密碼：").strip()
inp_money = input("請輸入您的餘額：").strip()
​
with open('db.txt', mode='at', encoding='utf-8') as f:
  f.write('%s:%s:%s\n' % (inp_user, inp_pwd, inp_money))
​
​
​
轉賬
import os
​
with open('db.txt',mode='rt',encoding='utf-8') as f1,open('.db.txt.swp',mode='wt',encoding='utf-8') as f2:
  for line in f1:
    user,pwd,money = line.strip('\n').split(':')
    if user == 'tom':
      money = int(money) - 100
    elif user == 'lili':
      money = int(money) + 100
​
    line = "%s:%s:%s\n" % (user, pwd, money)
    f2.write(line)
​
os.remove('db.txt')
os.rename('.db.txt.swp','db.txt')
​
 

五、檔案讀寫的其他方法

with open('b.txt',mode='rt',encoding='utf-8') as f:
  print(f.readable())  是否可讀
  print(f.readline())  讀取一行內容,游標移動到第二行首部
  print(f.readlines()) 讀取每一行內容,存放於列表中
​
  lines = f.readlines()
  print(lines[0])
​
​
with open('b.txt', mode='wt', encoding='utf-8') as f:
  print(f.writable())
​
  lines = ['你好\n', '我好\n', '大家好\n']
​
  for line in lines:
    f.write(line)
  f.writelines(lines)
​
  f.write('1111\n222\n333\n')
​
​
  f.write('hello')
  f.writelines('hello')
​
  f.flush()   立刻將檔案內容從記憶體刷到硬碟
​
​
​
with open('b.txt', mode='at', encoding='utf-8') as f:
  f.truncate(3)  

六、控制檔案指標移動

儲備知識：只有t模式下的read(n)的n代表的是字元個數，除此以外都代表位元組個數
with open('b.txt',mode='rt',encoding='utf-8') as f:
  print(f.read(4))  從第4個字元的位置讀到檔案末尾
​
​
with open('b.txt',mode='rb') as f:
  print(f.read(3).decode('utf-8'))
​
​
f.seek(移動的位元組個數,模式)
模式：
0：參照檔案開頭,只有0模式可以在t下使用，其他的都只能在b下使用
with open('b.txt',mode='rt',encoding='utf-8') as f:
  f.seek(3,0)
  f.seek(6,0)
  print(f.tell())  檢視當前指標距離檔案開頭的位置
​
1：參照指標當前所在的位置，只能在b下使用
with open('b.txt',mode='rb') as f:
  f.seek(3,1)
  f.seek(6,1)
  print(f.tell())
​
2：參照指標檔案末尾，通常是倒著移動，只能在b下使用
with open('b.txt',mode='rb') as f:
  f.seek(-5,2)
  f.seek(-8,2)
  print(f.tell())
  print(f.read().decode('utf-8'))