what is file?
virtual unit offered by operation system
steps to open file
1.find the file_path(file_path)
2.open file(open)
3.read or change the file(read/write)
4.save the files(flush)
5.close the file (close)
three modes to open .txt file
w：clear the file and write in
r：can only read
a:write in after the file
two ways to open .txt file
b：binary
t：text
you'd better not to use three ways below
1.r+
2.a+
3.w+
with in charge of the context
f=open()
f.read()
#close file automaticly
with open() as f
f.read()
principle of crawler
send requests through explore to get files，through requests module analog browser gets content
process of crawler
1.send requests（filling url）
2.get context
3.choose the value you need
use of requests module
import requests
res=requests.get(url)
#wenben
res.txt
#erjinzhiliu
res.content
re module
re.S search all
re.findall() choose what you need in the context
if you need anything just(.*?)