Python3学习之路~2.7 文件操作

Somehow, it seems the love I knew was always the most destructive kind

不知为何，我经历的爱情总是最具毁灭性的的那种

Yesterday when I was young

昨日当我年少轻狂

The taste of life was sweet

生命的滋味是甜的

As rain upon my tongue

就如舌尖上的雨露

I teased at life as if it were a foolish game

我戏弄生命 视其为愚蠢的游戏

The way the evening breeze

就如夜晚的微风

May tease the candle flame

逗弄蜡烛的火苗

The thousand dreams I dreamed

我曾千万次梦见

The splendid things I planned

那些我计划的绚丽蓝图

I always built to last on weak and shifting sand

但我总是将之建筑在易逝的流沙上

I lived by night and shunned the naked light of day

我夜夜笙歌 逃避白昼赤裸的阳光

And only now I see how the time ran away

事到如今我才看清岁月是如何匆匆流逝

Yesterday when I was young

昨日当我年少轻狂

So many lovely songs were waiting to be sung

有那么多甜美的曲儿等我歌唱

So many wild pleasures lay in store for me

有那么多肆意的快乐等我享受

And so much pain my eyes refused to see

还有那么多痛苦 我的双眼却视而不见

I ran so fast that time and youth at last ran out

我飞快地奔走 最终时光与青春消逝殆尽

I never stopped to think what life was all about

我从未停下脚步去思考生命的意义

And every conversation that I can now recall

如今回想起的所有对话

Concerned itself with me and nothing else at all

除了和我相关的 什么都记不得了

The game of love I played with arrogance and pride

我用自负和傲慢玩着爱情的游戏

And every flame I lit too quickly, quickly died

所有我点燃的火焰都熄灭得太快

The friends I made all somehow seemed to slip away

所有我交的朋友似乎都不知不觉地离开了

And only now I'm left alone to end the play, yeah

只剩我一个人在台上来结束这场闹剧

Oh, yesterday when I was young

噢 昨日当我年少轻狂

So many, many songs were waiting to be sung

有那么那么多甜美的曲儿等我歌唱

So many wild pleasures lay in store for me

有那么多肆意的快乐等我享受

And so much pain my eyes refused to see

还有那么多痛苦 我的双眼却视而不见

There are so many songs in me that won't be sung

我有太多歌曲永远不会被唱起

I feel the bitter taste of tears upon my tongue

我尝到了舌尖泪水的苦涩滋味

The time has come for me to pay for yesterday

终于到了付出代价的时间 为了昨日

When I was young

当我年少轻狂

f=open("yesterday.txt",encoding='UTF-8') #打开文件句柄

print(f.read()) #打印全部,读完之后，指针在文件最后，下次读时从文件最后开始读

for i in range(5):

        print(f.readline()) #打印前5行，读完之后，指针在文件第5行后，下次读时从文件第5行开始读

print(f.readlines()) #将文件作为一个列表读出来，每一行代表一个元素

#循环打印所有行，low的写法

# 吃内存，内存保存全部行，需要将全部行写入内存后再一行行地读，当文件较大时，我们等待时间变长，并且内存也吃不消了

for line in f.readlines():

        print(line.strip()) 

#循环打印除第10行之外的所有行，low的写法

for index,line in enumerate(f.readlines()):

        if index==9:

                print('-------我是分割线----------')

                continue

        print(line.strip())

#循环打印所有行，high的写法

#效率高，文件变成一个迭代器，读一行内存中删一行，内存中只保存一行，牛B了

for line in f:

        print(line.strip())

#循环打印除第10行之外的所有行，high的写法

count=0

for line in f:

        if count == 9:

                print('-------我是分割线----------')

                count+=1

                continue

        print(line.strip())

        count += 1

print(f.tell()) #打印指针位置，开始位置0

print(f.read(5)) #读文件的5个字符

print(f.tell()) #此时指针位置是5

print(f.seek(0)) #指针回到位置0

print(f.readline()) #从头开始打印第一行

print(f.seekable()) #判断是否可以移动文件的光标位置，如果可以（比如说二进制，字符串文件），返回True，否则返回False

                    #并不是所有的文件都是可以把光标移动的，因为Linux是一切皆文件，比如说tty文件就是不可以的

print(f.encoding) #打印文件的编码格式

print(f.fileno()) #返回文件句柄在内存中的编号，我们一般不会用到它

                  # 操作系统有一个专门的接口，负责调度所有文件。Python读文件不是自己读的，是调用操作系统的IO，

                  # 操作系统内部维护了一个类似于现在读了多少文件之类的列表，这就是在其中的编号。

print(f.name) #打印文件名字

print(f.isatty()) #判断文件是否是一个终端设备，比如说打印机、Linux上打开的terminal都属于终端设备，

                  # 这个是你做一些底层的，比如说和打印机交互等可能会用得到。

print(f.readable()) #判断文件是否可读

print(f.writable()) #判断文件是否可写

print(f.cloed) #判断文件是否已关闭

f.close() #对文件操作完之后，一定要关闭文件

#写文件时，是先将内容写入一个缓存中，当缓存满时再一次性将所有内容写入硬盘

#flush()作用是强制将内容刷新到硬盘

>>> f=open('test.txt','w')

>>> f.write('hello1\n') #此时打开test.txt文件，发现文件为空

7

>>> f.flush() #重新打开文件，文件显示一行hello1

>>> f.write('hello2\n') #重新打开文件，文件未变还是只显示一行hello1

7

>>> f.flush() #重新打开文件，发现hello2已写入文件

>>> f.close()

import sys,time

for i in range(20):

    sys.stdout.write('#')

    sys.stdout.flush() #如果没有这一句，则程序时先将所有的#写到缓存中，再一次性输出

    time.sleep(0.2)

f=open("yesterday2.txt",'a',encoding='UTF-8') #文件句柄

f.seek(5)

f.truncate(10) #截取前10个字符，此时打开文件发现只剩前10个字符

               #此处seek方法没有作用，truncate方法默认就是从文件开头开始截取

f.close()

def close(self): # real signature unknown; restored from __doc__

        """

        Close the file.

        A closed file cannot be used for further I/O operations.  close() may be

        called more than once without error.

        """

        pass

    def fileno(self, *args, **kwargs): # real signature unknown

        """ Return the underlying file descriptor (an integer). """

        pass

    def isatty(self, *args, **kwargs): # real signature unknown

        """ True if the file is connected to a TTY device. """

        pass

    def read(self, size=-1): # known case of _io.FileIO.read

        """

        注意，不一定能全读回来

        Read at most size bytes, returned as bytes.

        Only makes one system call, so less data may be returned than requested.

        In non-blocking mode, returns None if no data is available.

        Return an empty bytes object at EOF.

        """

        return ""

    def readable(self, *args, **kwargs): # real signature unknown

        """ True if file was opened in a read mode. """

        pass

    def readall(self, *args, **kwargs): # real signature unknown

        """

        Read all data from the file, returned as bytes.

        In non-blocking mode, returns as much as is immediately available,

        or None if no data is available.  Return an empty bytes object at EOF.

        """

        pass

    def readinto(self): # real signature unknown; restored from __doc__

        """ Same as RawIOBase.readinto(). """

        pass #不要用,没人知道它是干嘛用的

    def seek(self, *args, **kwargs): # real signature unknown

        """

        Move to new file position and return the file position.

        Argument offset is a byte count.  Optional argument whence defaults to

        SEEK_SET or 0 (offset from start of file, offset should be >= 0); other values

        are SEEK_CUR or 1 (move relative to current position, positive or negative),

        and SEEK_END or 2 (move relative to end of file, usually negative, although

        many platforms allow seeking beyond the end of a file).

        Note that not all file objects are seekable.

        """

        pass

    def seekable(self, *args, **kwargs): # real signature unknown

        """ True if file supports random-access. """

        pass

    def tell(self, *args, **kwargs): # real signature unknown

        """

        Current file position.

        Can raise OSError for non seekable files.

        """

        pass

    def truncate(self, *args, **kwargs): # real signature unknown

        """

        Truncate the file to at most size bytes and return the truncated size.

        Size defaults to the current file position, as returned by tell().

        The current file position is changed to the value of size.

        """

        pass

    def writable(self, *args, **kwargs): # real signature unknown

        """ True if file was opened in a write mode. """

        pass

    def write(self, *args, **kwargs): # real signature unknown

        """

        Write bytes b to file, return number written.

        Only makes one system call, so not all of the data may be written.

        The number of bytes actually written is returned.  In non-blocking mode,

        returns None if the write would block.

        """

        pass

#VIM修改文件的方式：先把文件读到内存中，在内存中修改，之后再把修改后的文件读出来覆盖原文件

#另一种修改文件的方式，将文件修改后，写到另一个新文件中,如下

f=open("yesterday.txt",'r',encoding='UTF-8')

f_new=open("yesterday.bak",'w',encoding='UTF-8')

for line in f:

    if "有那么多肆意的快乐等我享受" in line:

        line=line.replace("有那么多肆意的快乐等我享受","有那么多肆意的快乐等Alex享受")

    f_new.write(line)

f.close()

f_new.close()