python文件的使用方法

文件的类型
文件是存储在辅助存储器上的数据序列
文件是数据存储的一种形式
文件展现形态：文本文件和二进制文件

本质上所有文件都用二进制形式形式存储。文本文件是由单一特定编码组成的文件，二进制文件直接由0和1组成，没有特定的编码。

文件的打开和关闭
<变量名> = open(<文件名>, <打开模式>)
源文件和程序在同一目录下可以省略路径（即使用相对路径），否则需要使用绝对路径。

file=open('meimei.txt','r')   #相对路径，只读
file=open('C:Users/lenovo/coding/meimei.txt','r')   #绝对路径，只读

(图片来自北理工嵩天python慕课）
文件的关闭

file=open('F:meimei.txt','r')
print(file.read())
file.close()   #文件的关闭

文件内容的读取
文件内容的读取主要有三种方式，分别是read，readline，和readlines函数
三种方式各有特点

操作方法	描述
file.read(size=-1)	读入全部内容，如果给出参数，读入前size长度
file.readline(size=-1)	读入一行内容，如果给出参数，读入该行前size长度
file.readlines(hint=-1)	读入文件所有行，以每行为元素形成列表如果给出参数，读入前hint行

文件的全文本读取
（一次读取全部文本内容）

file=open('F:meimei.txt','r')
print(file.read())
file.close()

We can leave the Christmas lights up 'til January
This is our place we make the rules
And there's a dazzling haze
A mysterious way about you dear
Have I known you 20 seconds or 20 years
Can I go where you go
Can we always be this close
Forever and ever
And ah take me out
And take me home
You're my my my my
Lover

（读取全部文本内容并形成列表）

file=open('F:meimei.txt','r')
print(file.readlines())
file.close()

["We can leave the Christmas lights up 'til January\n", 'This is our place we make the rules\n', "And there's a dazzling haze\n", 'A mysterious way about you dear\n', 'Have I known you 20 seconds or 20 years\n', 'Can I go where you go\n', 'Can we always be this close\n', 'Forever and ever\n', 'And ah take me out\n', 'And take me home\n', "You're my my my my\n", 'Lover']

文件的逐行读取

（readline方法）

file=open('F:meimei.txt','r')
txt=file.readline()    #分行读入，逐行处理
for txt in file:
    print(txt)
file.close()

This is our place we make the rules

And there's a dazzling haze

A mysterious way about you dear

Have I known you 20 seconds or 20 years

Can I go where you go

Can we always be this close

Forever and ever

And ah take me out

And take me home

You're my my my my

Lover

(read方法）


file=open('F:meimei.txt','r')
txt=file.readlines()   #一次读入，分行处理
for line in txt:
    print(line)
file.close()

read和readlines方法都是一次性读入整个文件，如果文件的规模特别大，可能会直接破坏软件，所以一般的小文件可以直接读取，较大的文件使用readline逐行读取，或者可以采取切片的方式。

file=open('F:meimei.txt','r')
print(file.read(100))
file.close()

We can leave the Christmas lights up 'til January
This is our place we make the rules
And there's a

文件的读取还可以使用with open 方式，示例如下

path='F:meimei.txt'
with open(path,'r') as file:
    txt=file.read()
print(txt)
file.close()

数据的文件写入

path='F:meimei.txt'
file=open(path,'a')  #追加写模式
txt=file.write('I love meimei\n')
file.close()

file=open(path,'r') 
print(file.read())
file.close()

We can leave the Christmas lights up 'til January
This is our place we make the rules
And there's a dazzling haze
A mysterious way about you dear
Have I known you 20 seconds or 20 years
Can I go where you go
Can we always be this close
Forever and ever
And ah take me out
And take me home
You're my my my my
Lover
I love meimei

path='F:meimei.txt'
file=open(path,'a')    #追加写模式
lis=['meimei\n','taylor\n','swift\n']
file.writelines(lis)
file.close()

file=open(path,'r') 
print(file.read())
file.close()

We can leave the Christmas lights up 'til January
This is our place we make the rules
And there's a dazzling haze
A mysterious way about you dear
Have I known you 20 seconds or 20 years
Can I go where you go
Can we always be this close
Forever and ever
And ah take me out
And take me home
You're my my my my
Lover

meimei
taylor
swift