爬虫基础之文件操作

打开文件

f = open("test_01")
# print(f.read())		#返回全部内容
# print(f.readlines())	#返回每一行内容
print(f.readline())		#返回每一行内容，每次指针下移一行
print(f.readline())
f.close() 				#每次用完文件需要关闭

写入文件

f = open("test_01", "w")
# f.write("tesstssss")				#改写入全部内容
f.writelines(["first\n","second"])	#改写入多行内容
f.close()

========= ===============================================================
Character Meaning
--------- ---------------------------------------------------------------
'r'       open for reading (default)
'w'       open for writing, truncating the file first
'x'       create a new file and open it for writing
'a'       open for writing, appending to the end of the file if it exists
'b'       binary mode
't'       text mode (default)
'+'       open a disk file for updating (reading and writing)
'U'       universal newline mode (deprecated)
========= ===============================================================

‘b’ binary mode

什么时候用 b

一般情况下，读写文件是文本格式，用“w”和“r”，当是图片、音频、压缩包等，用“wb”和“rb”。

open 不用关闭的方法（常用）

with open("test_01") as aaa:
	print(aaa.read())

with open("test_01", "a") as bbb:
	bbb.write("dfkjlafjdkf")

with open("a.png", "rb") as ccc:
	with open("c.png","wb") as ddd:
		ddd.write(ccc.read())