python  文件的基本操作 菜中菜功能的实例代码

​ f :文件句柄
f = open("1.txt",mode = 'r',encoding = 'utf-8')
print(f.read())
f.close

f = open('1.txt','r')
print(f.read()) #全部读取
print(f.read(5))#按照字符进行读取，前5个
print(f.readline())#读取一行内容，自动换行
print(f.readline().strip())#拖\n
print(f.readlines())#一行一行读，存为列表

#解决大文件：
for i in f:
  print(i)#本质就是一行一行进行读取

1.先清空文件
2.写入文件
f = open('1.txt','w',encoding='utf-8')
f.write('13030308\n')
f.write('456456\n')
f.close()

#在源文件的基础上进行添加
f = open('1.txt','a',encoding='utf-8')
f.write('13030308\n')
f.write('456456\n')
f.close()

#rb:
f1 = open('1.jpg','rb')
print(f1.read())
print(f1.read(3))#按照字节读取，读取前3个字节
#wb:
f = open('3.jpg','wb')
f.write(f1.read())
#ab:
f = open('2.jpg','ab')
f.write('你好啊',encode = 'utf-8')

1. r+:读写。应该先读后写
#错误示范
f = open('1.txt','r+','utf-8')
#f = write('cx你太美')
#print(f.read())
#正确
print(f.read())
f = write('cx你太美')

#读不到内容
f = open('1.txt','r+','utf-8')
f = write('cx你太美')#光标问题
print(f.read())

#读不到内容
f = open('1.txt','r+','utf-8')
f = write('cx你太美')#光标问题
print(f.read())

print(f.tell())#显示光标位置，返回的是字节数
f.seek(0)#移动光标

f =open('1.txt','r','utf-8')
#for i in f:
s = f.read()
s1 = s.replace('12','45')
f.close()
f1 =open('1.txt','w','utf-8')
f1.write(s1)
f1.close() 

with open('1.txt','r','utf-8') as f,\
open('1.1.txt','w','utf-8') as f1:
  for i in f:
    s1 =i.replace('12','45')
    f1.write(s1)
import os 
os.rename('1.txt','1.bak')
os.rename('1.1.txt','1.txt')

f = open("E:\\python\\oldboy\\py\\190715",'r','utf-8')
#路径转义：1.'\\'
#2.r。-->repr()：数据的原形态
#s = "[1,2,'3',4]"
#print(s)
#print(repr(s))#--显示数据原形态
f = open(r"E:\python\oldboy\py\190715",'r','utf-8')
print(f.read())
f.close()
1.相对路径
f = open("../190713/1.txt",'r','utf-8')
print(f.read())
f.close()
#推荐使用相对路径