文件处理

1、文件读写：

file = open('file_name.txt','w',encoding='utf-8')
names = ['a','b','c']
n='wang,123'
file.write(n)   #多用于字符串
#file.writelines(n)
for name in names:
    file.write(name)
#for name in names:
#    file.writelines(names)

import time
file = open('hahaha','w')
file.write('kakaka')
file.flush() 　　#立即把缓冲区里面的内容写到磁盘里面

with open('file_name.txt','w') as a , open('file_name2.txt') as a2:   #打开多个文件
    a.write('123')
    a2.write('456')

2、以二进制模式打开图片：

import requests
url = 'https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1515746419895&di=9aa9a8429799de178ba0cc9cf06c89e9&imgtype=0&src=http%3A%2F%2Fimg.zcool.cn%2Fcommunity%2F01a2e6567ce0bd6ac725ad903aa9bb.jpg'
img = requests.get(url).content
f = open('xiaohei.jpg','wb')　　#bytes，以二进制模式打开
f.write(img)

3、修改文件两种方式：

1/
with open('nums', 'a+', encoding='utf-8') as f:
    f.seek(0)
    all = f.read()
    new_num = all.replace('1', '2')  #a为旧字符串，b为新字符串
    f.seek(0)
    f.truncate()
    f.write(new_num)
    f.flush()

2/
import os
with open('nums',encoding='utf-8') as f, open('nums.gy','w',encoding='utf-8') as f2:
    for line in f:
        new_line = line.replace('1', '2')
        f2.write(new_line)
os.remove('nums')                #删文件
os.rename('nums.gy', 'nums')    #改名