Python打开文件、文件读写操作、with方式、文件常用函数实例分析

open(file, mode='r', buffering=None, encoding=None, errors=None, newline=None, closefd=True)

file--文件名

mode—打开模式，默认只读模式

buffering--如果buffering的值被设为0，就不会有寄存。如果buffering的值取1，访问文件时会寄存行。如果将buffering的值设为大于1的整数，表明了这就是的寄存区的缓冲大小。如果取负值，寄存区的缓冲大小则为系统默认。

encoding—打开文件的编码方式 

print("r".center(50,'-'))
f=open("file.txt",encoding="utf-8")
print(f.read())
f.close()
-----------------
运行结果：
my
sas
aaa
fsafsa
中文
中文
葫芦娃

print("r".center(50,'-'))
f=open("file.txt",encoding="utf-8")
print(f.read())
f.close()
---------------------------
运行结果：
my
sas
aaa
fsafsa
中文
中文
葫芦娃

print("r".center(50,'-'))
f=open("file.txt",encoding="utf-8")
print(f.readline())
f.close()

-----------
运行结果：
my

print("r".center(50,'-'))
f=open("file.txt",encoding="utf-8")
print(f.readlines())
f.close()




#------------------------r-------------------------
#运行结果：
['my\n', 'sas\n', 'aaa\n', 'fsafsa\n', '中文\n', '中文\n', '葫芦娃\n', '\n']

print("r".center(50,'-'))
f=open("file.txt","r+",encoding="utf-8")
# print(f.readline())
f.write("hello mike")
f.close()

print("r".center(50,'-'))
f=open("file.txt","r+",encoding="utf-8")
print(f.readline())
f.write("hello mike")
f.close()

myfile=open("myfile1","wb")
myfile.write(b"nnnnnn")
myfile.write("my葫芦娃".encode("utf-8"))
myfile.close()

myfile=open("myfile1","wb")
myfile.write(b"nnnnnn")

myfile.writelines([b'1',b'2',b'3',b'4'])
myfile.close()

myfile=open("myfile1","wb+")
myfile.write(b"nnnnnn")
myfile.seek(0)
print(myfile.read())
myfile.close()

myfile=open("myfile1","wb+")
myfile.write(b"1nnnnnn")
site=myfile.tell()
myfile.write(b"2nnnnnn")
myfile.seek(site)##读出后一段
print(myfile.read())
myfile.close()

with open("file.txt","r+",encoding="utf-8") as f:##将自动执行f.close()
 print(f.tell())
 f.write("金刚")
 for line in f:
  print(line,end="")

with open("file.txt",'r') as f ,\
open("file.new",'r') as m:
 print(f.read(),m.read())

myfile=open("myfile1","wb+")
myfile.write(b"1nnnnnn")
site=myfile.tell()
myfile.write(b"2nnnnnn")
myfile.seek(site)##读出后一段
print(myfile.read())
myfile.close()

import time
myfile=open("myfile1","wb+")
myfile.write(b"1nnnnnn")
time.sleep(10)
# myfile.flush()
myfile.write(b"2nnnnnn")
myfile.close()

import time
myfile=open("myfile1","wb+")
myfile.write(b"1nnnnnn")
myfile.flush()
time.sleep(10)
myfile.write(b"2nnnnnn")
myfile.close()

print("r".center(50,'-'))
f=open("file.txt","r+",encoding="utf-8")

print(f.readline())
print("----truncate()-------")
print(f.tell())
m=f.tell()
f.truncate(m)#内容从0位置截断到指定位置，不论当前光标位置
f.close()